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Fracture behavior of additively manufactured acrylonitrile butadiene styrene (ABS) materials
Abstract
The effect of layer orientation on the fracture properties of poly(acrylonitrile-butadienestyrene) (ABS) materials fabricated through the fused filament fabrication (FFF) process was explored. Critical elastic-plastic strain energy release rates of single edge notch bend (SENB) specimens with variable crack-tip/laminae orientations were compared. Results show that the inter-laminar fracture toughness (fracture between layers) is approximately one order of magnitude lower than the cross-laminar toughness (fracture through layers) of similarly manufactured parts. Contrasting brittle and ductile fracture behavior is observed for inter-laminar and cross-laminar crack propagation, respectively, demonstrating that the elastic-plastic response of AM ABS parts is governed by the direction of crack propagation within the laminated structure. Fracture surfaces of failed specimens are examined using scanning electron microscopy to show micro- and macro-scale toughening/embrittling mechanisms. Techniques for designing tougher additively manufactured materials based on biological analogies are discussed.
... The fracture properties of AM polymers appear in Refs. [25][26][27], providing a benchmark and good understanding of the fracture behavior of AM parts that enable the structural design based on damage tolerance criteria. Rodriguez and Thomas [25] obtained a energy release rate, i.e., the energy required by the cracked material to initiate a fracture (also known as energy release rate), of 3D printed ABS as measured using single edge notch specimens under tension (SENT) to be 0.24-0.88 ...
... kJ/m 2 with a noticeable degree of anisotropy due to the raster orientation. In other work, Hart and Wetzel [26] reported values of interlaminar energy release rate of 3D printed ABS at 0.25 kJ/m 2 . In comparison, the crosslaminar energy release rate was 2.26 kJ/m 2 , exposing the anisotropy of the fracture behavior in ABS. ...
... As the crack propagates, a local 'whitening' (i.e., crazing [54]) develops ahead of the crack tip in ABS. Here, the energy density required to grow the crack is partly transformed into building an elastoplastic regime around the crack [26]. Internally, crazing is developed due to the stretching of multiple nanofibrils around microvoids during plastic deformation [55]. ...
Large-Area Additive Manufacturing (LAAM) has seen increased application in manufacturing meter-scale, polymeric composite structural parts, especially for tooling and fixturing. Unfortunately, LAAM introduces manufacturing-induced defects in printed composites, e.g., intrabead microvoids and poor interbead adhesion that are not otherwise seen when traditional manufacturing methods are used, causing degradation of mechanical and fracture properties. In this paper, the fracture behavior of neat acrylonitrile butadiene styrene (ABS) and short carbon fiber-reinforced ABS (CF/ABS) fabricated by LAAM is compared and analyzed by evaluating their energy release rate and fracture mechanisms. A double cantilever beam with doublers (DCB-D) test for single-bead, double-bead, and multiple-bead configurations is developed by incorporating rigid doublers to reduce the compressive failure at the crack tip, allowing for the measurement of crack propagation. A new data reduction method for these configurations is derived to remove the doubler effect from the calculation, producing ‘pure’ intrabead and interbead values. We show that CF/ABS is more damage tolerant than ABS at the intrabead level, but less damage tolerant than ABS at the interbead level. The development of plastic ligaments in ABS helps dissipate additional strain energy, improving the overall energy release rate. The experimental fracture test approach developed here is expected to provide mechanistic insight into their damage tolerance capability, accelerating the qualification process of LAAM-produced polymer and polymer composites.
... Additionally, strength and fracture toughness of AM parts are often anisotropic. [2][3][4][5][6][7][8][9][10][11][12][13][14][15] It is crucial to understand fracture toughness of AM polymers to ensure their reliability and durability. To this end, this study considers three common AM polymers and two of the most widely used AM techniques for polymers: fused filament fabrication (FFF) and selective laser sintering (SLS). ...
... The effect of the build direction on the fracture properties of FFF-ABS polymers has been studied by Hart and Wetzel. 3 They found that the fracture toughness inside the layers (intralayer) was 1 order of the magnitude higher than between the layers (interlayer). ...
... Another study introduced a hole in front of the initial crack, totally changing the stress field of the initial crack. 3 Therefore, this study presents accurate mode-I fracture toughness measurements of three AM polymers based on complete understanding of fracture mechanics. To resolve the K IC measurement issue described here, this study examines (1) the anisotropic and elastoplastic nature of fracture toughness, (2) the fracture toughness reduction between bulk and AM polymers, and (3) the effect of the AM technique on the fracture toughness of polymers. ...
Two types of additive manufacturing (AM) techniques, fused filament fabrication (FFF) and selective laser sintering (SLS), were employed to fabricate specimens from three widely used AM polymers: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyamide (PA): the first two using FFF and PA using SLS. The single‐edge notch bending (SENB) test was employed to measure the mode‐I fracture toughnesses of bulk and AM specimens in three directions relative to the printing direction. Unlike their bulk counterparts, AM polymers exhibited anisotropic fracture toughness. The degree of anisotropy in FFF‐PLA was much larger than FFF‐ABS and SLS‐PA. The smallest fracture toughness value for each AM polymer was achieved along the transverse printing direction. Different AM techniques affect fracture toughness differently. For instance, FFF is shown to increase PLA's plastic deformation, while SLS reduces PA's ductility. The decrease in fracture toughness is consistently observed when transitioning from bulk polymers to AM ones, reaching as much as 75%. This study provides insights into the fracture toughness of AM parts made via popular plastics, which are crucial for designing structural parts using FFF and SLS processes.
... Many studies have carried out optimization of process parameters for achieving desirable mechanical properties [20][21][22][23][24][25][26][27]. In particular, fracture resistance of 3D-printed PLA has been studied for different raster angles, and the +45 deg/−45 deg stacking sequence has been found to have the highest crack initiation resistance, while the 0 deg/90 deg sequence has been reported to have the lowest [21,25]. ...
... In particular, fracture resistance of 3D-printed PLA has been studied for different raster angles, and the +45 deg/−45 deg stacking sequence has been found to have the highest crack initiation resistance, while the 0 deg/90 deg sequence has been reported to have the lowest [21,25]. Other studies have shown that the initiation fracture toughness is highest when the crack is perpendicular to the printed layer and lowest when it is parallel to the same, with intermediate values for a 45 deg orientation [24,28]. ...
... The SENB follows the ASTM D6068, with a length-to-width ratio of at least 6. However, the crack length-to-width ratio was kept at 0.2, which is smaller than the recommended value of 0.5 [24]. This is to enable measurement of R-curve behavior and total work of fracture (WOF) as the crack grows. ...
3D printing is a layer by layer deposition process, which results in highly anisotropic structures, and contain interfaces. Complex shapes manufactured by 3D printing carry defects. Complete elimination of these defects and interfaces is not possible, and these defects degrade the mechanical properties. In the present study, mechanical properties of printed dog bone samples are quantified as a function of building parameters, in particular, filling patterns, raster angle, and orientation of build direction with respect to that of loading, in polylactic acid (PLA). The tensile strength of 3D printed PLA is the same for hexagonal and linear pattern filling when build direction is along thickness and width, and failure was initiated at the defects in the structure, while better overall toughness is offered by hexagonal pattern filling. Build direction along specimen gauge length gives very low tensile strength and toughness, and failure happens between the printing layers. To minimize the defects especially near the grip section, cuboid sample were first deposited, and micro-machined by laser into dog bone shape to perform tension test. Tensile strength and elastic modulus of micro-machined samples are surprisingly lower, while failure strain is highest among line filling printed samples. Damage resistance was quantified in terms of work of fracture, and hexagonal filling provided better damage resistance than line filling patterns for conditions of 0º raster angle with respect to the crack whereas line filling with 45º and 90º raster angle tolerated damage better than hexagonal filling.
... The fracture properties of AM polymers and composites have been measured experimentally by several authors [4][5][6], which have been shown to provide a good understanding of the fracture behavior of AM parts that enables the structural design based on damage tolerance criteria. For example, the fracture toughness (i.e., energy required by the cracked material to initiate a fracture) of 3D printed unfilled/neat ABS, as measured using single edge-notch specimens under tension (SENT), was found to be 0.24-0.88 ...
... kJ/m 2 [4] with a noticeable degree of orthotropy due to the raster orientation. Hart and Wetzel [5] found that the fracture of 3D-printed neat ABS also exhibited an orthotropy response where the measured fracture toughness was 0.25 kJ/m 2 for inter-laminar and 2.26 kJ/m 2 for cross-laminar. A higher print speed of 70 mm/s improved the fracture toughness of 3D-printed ABS with measured values up to 4.1 kJ/m 2 [6]. ...
This paper proposes an efficient experimental method to measure the mode I fracture toughness of large-area additive manufactured polymeric composites. By utilizing either single-bead or double-bead systems bonded to the double cantilever beam (DCB) configuration, we measure intrabead and interbead fracture toughness of acrylonitrile butadiene styrene (ABS) and short carbon fiber-reinforced ABS. The effect of rigid doublers (which are used to eliminate a premature compressive failure) is excluded in the calculation of total energy dissipation, producing a purely interlayer fracture toughness. We found that the critical fracture toughness of carbon fiber/ABS is lower than that of ABS due to the voids within and between the beads. The experimental and data reduction methods developed here can be utilized to optimize the interlayer adhesion of large-scale 3D printed materials.
... This chapter provides a general classification and detailed discussion on the use of collected MCM equipment. The following tables demonstrate the defect methods by diverse types of data acquisition equipment of MCM, including charge-coupled device (CCD) cameras in Table 7 [28,32,33,36,38,41,44,49,50,[95][96][97][98][99][100][101][102][103], optical microscopes in Table 8 [21, 39, 40, 44, 52, 70-72, 78, 104-107], scanning electron microscope (SEM) in Table 9 Fig. 12 Schematic of defect detection methodology Table 7 Defect study methods by using CCD Cameras [28,32,33,36,38,41,44,49,50,[95][96][97][98][99][100][101][102][103] [27,40,45,51,65,67,71,75,104,105,108,109], and cameras with embedded image processors in Table 10 [37,41,46,63,70,78,87,107,108,[110][111][112][113][114][115]. ...
... Holzmond and Li [37] applied the DIC technology to monitor the relative displacement and used the microscope to observe the optical pattern in polylactic acid (PLA) and ColorFabb Woodfill Fine filament. Hart and Wetzel [105] applied an optical microscope to locate the defects of 3D printed parts and investigated the nature of those defects via SEM micrographs. Garg and Bhattacharya [71] also applied the CCD camera and SEM to detect the defects. ...
Additive manufacturing (AM), also known as 3D printing (3DP), refers to manufacturing technologies that build up the desired geometries by adding materials layer by layer. Common meltable and fusible materials such as polymers, metals, and ceramics could be used in 3DP processes. During decades of development, products made by 3DP can now achieve stringent industrial standards at comparable costs compared to those traditionally manufactured. Improving 3DP technologies is required to make them more competitive and acceptable than their counterparts. However, achieving this is challenging since the quality of printing products is still heavily dependent on many cost-driven factors. Inadequate quality, impaired functionality, and reduced service life are three main consequences of 3DP’s failures. To effectively detect and mitigate defects and failures of 3DP products, machine condition monitoring (MCM) technologies have been used to monitor 3D printing processes. With the help of those dedicated algorithms, it could also prevent failures from occurrence by alerting operators to take appropriate actions accordingly. This study systematically reviews the MCM technologies used in a typical 3DP process—the fused deposition modelling (FDM), identifying their advantages and disadvantages. The mentioned MCM technologies include but are not limited to traditional MCM (sensors only), aided with analytical and artificial intelligence (AI) tools. The MCM techniques focus on the defects of the 3DP process. The detection and identification of those defects are investigated. Furthermore, research trends on developing MCM technologies, including challenges and opportunities, are identified for improving the FDM process. This review highlights the developed methodologies of MCM that are applied to FDM processes to detect and identify abnormalities such as defects and failures. The evaluations of defects are elaborated to deepen the comprehension of the essence of the defects, including their cause, severity, and effect. A detailed deliberation about identifying the critical components for the successful application of 3DP MCM systems was done. Finally, this review indicates the technical barriers that need to be overcome to enhance the performance of monitoring, detection, and prediction by MCM and associated technologies.
... mechanical properties of final 3D-printed part in z direction, and the interlayer adhesion strength is primarily dictated by the material's physical/chemical properties and the printing processing conditions. In recent years, several studies have characterized the fracture properties of single material MEX parts under mode I (opening mode) loading condition [13][14][15][16], which determines the overall interfacial bond strength. Some of the studies have utilized the American Society for Testing and Materials (ASTM) standards to characterize the fracture toughness of MEX parts [13,[16][17][18][19]. Aliheidari et al. characterized the apparent and true fracture resistance using a series of double cantilever beam (DCB) tests and quantifying the print meso-structure [15] to understand how each of the intrinsic layer-to-layer adhesion and print meso-structure contribute to the overall apparent fracture resistance. ...
... In recent years, several studies have characterized the fracture properties of single material MEX parts under mode I (opening mode) loading condition [13][14][15][16], which determines the overall interfacial bond strength. Some of the studies have utilized the American Society for Testing and Materials (ASTM) standards to characterize the fracture toughness of MEX parts [13,[16][17][18][19]. Aliheidari et al. characterized the apparent and true fracture resistance using a series of double cantilever beam (DCB) tests and quantifying the print meso-structure [15] to understand how each of the intrinsic layer-to-layer adhesion and print meso-structure contribute to the overall apparent fracture resistance. ...
Interface fracture in additively manufactured multi-materials is a leading cause of failure and it is critical to understand and characterize it. Here a simple methodology is presented to quantify the interfacial failure in additively manufactured acrylonitrile butadiene styrene (ABS) and thermoplastic polyurethane (TPU) bimaterials. Double cantilever beam (DCB) specimens were 3D-printed where a TPU layer is sandwiched between two ABS substrates. The printed specimens were loaded under mode I until failure, and the crack initiation load was identified using a verified stiffness drop method. This method overcame the significant crack blunting issues in visual crack detection methods, caused by the TPU inelastic deformation. A finite element model was used to obtain the J-integral fracture energy values. The measured fracture energy presented the adhesion strength between ABS and TPU, as the failure was purely adhesive in nature. The effect of the specimen geometry on the ABS/TPU interface fracture energy was then analyzed. It was found that the fracture energy is independent of the precrack length, but it is strongly affected by the TPU layer thickness, which was related to enlargement of the damage zone ahead of crack tip. This methodology provides a simple route to characterize interfacial adhesion in various additively manufactured multi-materials.
... Figure 1 illustrates this phenomenon, where the insufficient contact between deposited layers impedes the proper interlocking of polymeric chains, which is a critical mechanism for achieving Various methods have been employed to enhance this interlayer adhesion, including the optimization of printing parameters such as scanning speed, printing bed temperature, nozzle temperature, deposition rate, among others (Aliheidari et al., 2017;Johanson, 2016). Additionally, alternative approaches encompass the utilization of adaptive layer height algorithms (Allen and Trask, 2015), the introduction of plasticizers into the filament (Wang et al., 2014), microwave irradiation (Sweeney et al., 2017), or post-processing techniques like annealing (Hart et al., 2018;Bhandari et al., 2019). While these methods have demonstrated improvements in mechanical performance, it is noteworthy that the resultant properties often fall short of achieving the mechanical strength and toughness comparable to materials produced using more traditional methods such as injection molding. ...
... Figure 9 presents a comparison between the annealed flexural samples and the printed ones, focusing on material deformation. In all cases, an increase in thickness and a decrease in length were observed, which aligns with a common phenomenon occurring due to the crystallization process (Lluch-Cerezo et al., 2022) and the reorganization of voids (Hart et al., 2018) inherent to the printing process. Interestingly, condition B exhibited a notable increase in width, which differs from all other printing conditions. ...
... Although the overall fracture behaviour of FFF fabricated structures has been studied in many respects [40] (e.g. raster orientation [41,42]) and even on different length scales [43], there is a certain lack of understanding whether a crack prefers initial deflection or penetration, which greatly affects the overall failure later on. Therefore, the aim of this work was to clarify whether the Cook & Gordon and He & Hutchinson models, can contribute to a correct prediction of the actual crack progression, depending on processing parameters (T nozzle ) and thermal posttreatment. ...
... Several scientific contributions have been published addressing the macroscopic fracture behaviour of additively manufactured structures in recent years. Influences such as nozzle temperature [77], printing speed [78], build/raster orientation [41,42], thermal post-treatment [14], etc. on the failure mode are part of today's state of the art [40]. What still remains a gap in the understanding of fracture is how a crack initially propagates at the initiation stage. ...
... To this end, several studies have dealt with the effects of manufacturing parameters such as layer orientation [3][4][5], printing speed [6,7], raster angle [5,7], etc. on the fracture resistance of cracked FDM parts. Kevin et. ...
... Kevin et. al [4] assessed the mode I fracture toughness of Single Edge Notched Bend (SENB) specimens containing an arrest hole which was made of Acrylonitrile Butadiene Styrene (ABS) and printed in three different layer orientations, i.e. on-edge, upright, and oblique. Their experimental results revealed that the Load Carrying Capacity (LCC) of the specimens with upright layer orientation is considerably lower than that of the other counterparts. ...
This study deals with the effects of employing copper additives on the fracture resistance and fracture micro-mechanisms of 3D-printed Polylactic Acid (PLA) specimens under mixed mode I/II loading. Several comparative fracture tests are conducted on pre-cracked Semi-Circular Bend (SCB) specimens made of pure PLA and particulate copper-reinforced PLA (PLA/Cu) printed using the Fused Deposition Modeling (FDM) technique. The SCB specimens are fabricated in three different layer orientations. The comparison of the experimental results reveals that employing copper additives increases the load carrying capacities (LCCs) of the pre-cracked SCB specimens with the flat, on-edge, and upright layer orientations by 2.9%, 15.5%, and 27.7%, respectively. In addition, to determine the tensile properties of two desired materials, dogbone specimens made of PLA and PLA/Cu in three different layer orientations are fabricated and tested. The experimental results obtained from the characterization tests similarly indicate that the presence of copper additives in 3D printed PLA specimens increases ultimate tensile strength by 15.9%,14%, and, 10.4% in the three flat, on-edge, and upright layer orientations, respectively. Aside from performing experimental tests, the LCCs of pre-cracked specimens are predicted theoretically by utilizing Equivalent Material Concept (EMC) combined with the well-known Average Strain Energy Density (ASED) criterion. It is shown that the EMC-ASED criterion can estimate accurately the experimental LCCs of both FDM-PLA and FDM-PLA/Cu specimens. Finally, the Scanning Electron Microscope (SEM) technique is employed to provide a better understanding of the effects of copper additives on the micro-mechanisms of fracture.
... As a result, studying the fracture mechanics behavior of 3D-printed parts has drawn the interest of researchers in the last few years. The influence of the process parameters on the fracture behavior of ME-fabricated parts, such as thermal conditions of the process (Abeykoon et al., 2020;Aliheidari et al., 2018), infill density (Abeykoon et al., 2020), speed of printing (Abeykoon et al., 2020;Damodaran et al., 2018), layer thickness (Aliheidari et al., 2018;Somireddy et al., 2020), printing orientation (Li et al., 2018;Sedighi et al., 2019;Yap et al., 2019) and raster angle Cicero et al., 2021;Hart and Wetzel, 2017;Li et al., 2018;Oviedo et al., 2020;Verma et al., 2021;Yap et al., 2019) have been investigated in different articles. Cicero et al. (2022) presented a method for evaluating the structural integrity of 3D printed polymers using the notion of the failure assessment diagram in combination with the critical distance theory. ...
... As mentioned before, the ultimate tensile strength was considered as the material traction strength. The cohesive energy is equivalent to the fracture energy herein, which can be calculated using the below equation for plane strain conditions due to the brittle behavior of the material under study (Hart and Wetzel, 2017): Table 3 presents the values of the TSL parameters used in the simulations. The XFEM-CZM anisotropic damage model was developed for the FEA using two UDMGINI and USDFLD subroutines. ...
Purpose
The purpose of this study is to develop an efficient numerical procedure for simulating the effect of printing orientation, as one of the primary sources of anisotropy in 3D-printed components, on their fracture properties.
Design/methodology/approach
The extended finite element method and the cohesive zone model (XFEM-CZM) are used to develop subroutines for fracture simulation. The ability of two prevalent models, i.e. the continuous-varying fracture properties (CVF) model and the weak plane model (WPM), and a combination of both models (WPM-CVF) are evaluated to capture fracture behavior of the additively manufactured samples. These models are based on the non-local and local forms of the anisotropic maximum tangential stress criterion. The numerical models are assessed by comparing their results with experimental outcomes of 16 different configurations of polycarbonate samples printed using the material extrusion technique.
Findings
The results demonstrate that the CVF exaggerates the level of anisotropy, and the WPM cannot detect the mild anisotropy of 3D-printed parts, while the WPM-CVF produces the best results. Additionally, the non-local scheme outperforms the local approach in terms of finite element analysis performance, such as mesh dependency, robustness, etc.
Originality/value
This paper provides a method for modeling anisotropic fracture in 3D-printed objects. A new damage model based on a combination of two prevalent models is offered. Moreover, the developed subroutines for implementing the non-local anisotropic fracture criterion enable a reliable crack propagation simulation in media with varying degrees of complication, such as anisotropy.
... Among the fracture tests that have been performed on 3D printed specimens are compact tension, single and double edge notch tension [33,34], double cantilever beam, single edge notch bend, double edge notch tension [35,36], end-notched flexure [37,38], and semi-circular bend. Among the research on fracture behavior of 3D printed specimens, Kevin and Wetzel [39] investigated the impact of layer orientation on the fracture properties of a 3D printed single edge notch bend specimen made of ABS material. They saw that the inter-layer fracture toughness value is approximately 10% lower than the cross-layer fracture toughness value. ...
... In studied unidirectional 3D samples, which previously showed that the changing the failure mode between the interlayer and inlayer modes occurs at a printing angle of about 30 degrees, it is expected that the failure mode of M/90 • seen as inlayer failure and in M/45 • and M/ 0 • specimens seen as interlayer. Similar behavior was observed in other research, such as by Hart and Wetzel [39]. ...
This study aims to investigate the mechanical properties and crack resistance of unidirectional polylactic acid-based 3D printed components. In this regard, the effects of three printing angles (e.g., 0°, 45°, and 90°) and four ambient temperatures (e.g., −20, 0, 20, and 40 °C) on the tensile, flexural, and mode-I fracture characteristics were investigated. Additionally, utilizing theoretical theories appropriate for 3D printed samples as transversely isotropic samples, the results were assessed and expanded. Using the concepts of inlayer and interlayer failure modes in layered samples, the critical printing angle that separates the failure modes were evaluated. Also, failure patterns and the behavior of load-displacement curves were observed and assessed. The results show that an increase in temperature from − 20–40 °C caused tensile strength to decrease by 55–75%. Considering the samples isotropically, the strengths and energies were compared, then considering the anisotropy, inlayer, and interlayer tensile and shear strengths were reviewed. The results show that perpendicularly and transitively printed specimens have tensile strengths that are 4.4 and 2.5 times lower than parallel to loading direction printed specimens. Also, the critical printing angle is calculated as 23–31° based on the test temperature (respecting the load direction).
... Process parameters such as infill density and layer thickness significantly impact quality and surface finish [50]. The effect of layer height and infill on the mechanical characteristics of the component was also investigated [51]. Campbell et al. studied surface roughness for several materials; they reported that, in the case of ABS material, the surface roughness of the FDM process varies between 9 µm and 40 µm when a layer thickness of 0.253 mm is used [52]. ...
This study utilized a 3D printer that employed the photopolymer extrusion (PPE) technique with ultraviolet (UV) lasers to solidify a liquid-photosensitive polymer material. The research focused on studying fumed silica nanoparticles reinforced fillers with PPE, aiming for improved surface finish while maintaining desired rheological and mechanical properties for printing and application requirements. Various silica filler concentrations were examined during the experiments. It was noted that composite mixtures with fillers exceeding 10% exhibited significantly increased viscosity, rendering them unsuitable for extrusion in 3D printing applications. Additionally, it was observed that these mixtures displayed an increase in viscosity over time (aging), indicating a limited shelf-life. Non-contact profilometer results revealed enhanced values of roughness average (Ra) and root mean square average (Rq) for surface roughness in a 9% fumed silica mixture. This concentration resulted in superior surface properties compared to others, leading to improved print quality and higher strength overall; however, higher concentrations negatively impacted the bending properties of the printed samples.
Graphical Abstract
... at different magnifications. From Figure 6a,d, it can be observed that there are many voids in the cross-section of wABS, which is a result of the rubber particles' cavitation [40,41]. At the same time, it can be seen that aging has led to severe phase separation in wABS, with smooth interfaces and poor interfacial bonding strength, which is consistent with the poor mechanical performance results. ...
Adding a chain extender is one of the effective means to achieve high‐value recycling of waste acrylonitrile‐butadiene‐styrene (wABS). In this study, tris(4‐hydroxyphenyl)methane triglycidyl ether (TTE), with the small molecular structure and multiple epoxy groups, was used as a chain extender in wABS. The effects of TTE on the mechanical properties, molar mass, rheological behaviors, thermal stability, and fracture morphology were studied. The results showed that TTE extended the broken wABS chains, increased the molar mass, and improved the morphology of wABS/TTE, resulting in better performance in impact strength, tensile strength, storage modulus, loss modulus, complex viscosity, and thermal stability. When the content of TTE is 2.0 wt.%, the impact strength of the wABS/TTE blend increased to 28.5 kJ/m², which was a 20.8% increase compared with wABS, and both T 5% and T max2 in air had been improved, with each showing an increase of 5°C and 9°C, respectively, compared to wABS. The incorporation of TTE significantly enhanced wABS, improving interfacial bonding and providing better performance for wABS.
... They discovered that when the alignment of the extruded filament layers shifted from parallel to perpendicular to the crack plane, the fracture toughness significantly increased by 54%. Hart et al. 16 employed SENB samples to study the effect of layer orientation on the fracture properties of ABS. Their study emphasized the considerable anisotropy of fracture toughness due to the laminated structure of FFF-ABS components. ...
This study presents an experimental investigation to examine the mixed‐mode fracture behavior of fused filament fabrication printed acrylonitrile butadiene styrene (ABS). The single‐edge notch bending specimen configuration is employed to perform mixed‐mode fracture experiments. Four distinct printing orientations—90°, 0°, 45°/−45°, and 90°—are investigated. For each orientation, fracture studies are conducted under pure mode‐I loading (symmetric three‐point bending), mixed‐mode I/II, and pure mode‐II loading (asymmetric three‐point bending) to establish a mixed‐mode fracture criterion. The study evaluates the influence of printing orientation on fracture toughness, crack propagation behavior, and the mixed‐mode fracture criterion. Scanning electron microscopy (SEM) is utilized to analyze the fracture surfaces and correlate the observed fracture mechanisms with the measured fracture toughness values. The findings reveal that printing orientation significantly affects both the fracture toughness and the mixed‐mode fracture criterion. Among the orientations studied, the 90° specimens exhibit the highest fracture toughness and superior performance under all mixed‐mode conditions. SEM images of the fracture surfaces across different printing orientations show the formation of smooth shear zones of varying sizes near the crack tip under mixed‐mode and pure mode‐II conditions. These zones suggest an enhanced resistance to crack propagation, with the degree of improvement differing among the orientations.
Highlights
Mixed‐mode fracture behavior of 3D‐printed acrylonitrile butadiene styrene.
Printing orientations have a major influence on mixed‐mode fracture criterion.
90° printing orientation has the highest fracture toughness for mode‐mixities.
0° printing orientation has the lowest fracture toughness for mode‐mixities.
Fracture surface has dominant shear zone for all mode‐mixities except mode‐I.
... Once completed, the 3D model is split into hundreds or perhaps thousands of horizontal layers using specialized software. These layers are then fed to a 3D printer (which may interpret them differently depending on the model being used), which then uses a range of materials to print the object layer by layer, including plastics (ABS, PLA, PETG, etc.), resins, metals, and even ceramics (Hart, & Wetzel, 2017;Samiee & Azadi, 2018;Bardiya et al., 2021). Generally speaking, 3D printing and additive technology have become paradigm-shifting innovations. ...
... TPU-based flexible conductive filaments enable direct 3D printing onto textiles for electronic textile applications, offering flexibility that allows the printed material to bend and flex with the fabric [17]. Acrylonitrile butadiene styrene (ABS) is well-suited for durable applications [18], while thermoplastic elastomers (TPE), TPU, and thermoplastic copolyester (TPC) are known for their high durability and flexibility [19]. Nylon is commonly used for applications that demand long-lasting parts, such as tools, functional prototypes, or mechanical components [20]. ...
3D printing technology has made significant strides in smart textiles—fabrics embedded with electronics like conductive fibers and sensors—now widely applied in areas such as health con-dition monitoring, wearable energy-harvesting devices, and interactive textiles that respond to environmental conditions and color changes. Different 3D printing methods, such as Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), Direct Ink Writing (DIW), and PolyJet printing, are used in the fabrication of smart textiles. This study provides a detailed, applica-tion-specific overview of 3D printing technologies—such as FDM, SLS, DIW, and PolyJet print-ing—and their use in smart textiles across various sectors, including wearable technology, medical textiles, and smart fashion design. We gathered articles and reports from Scopus and Google Scholar, providing a concise assessment of 3D printing materials for smart textiles to give readers a quick understanding of the field. The timeline of 3D printing’s use in smart textiles, from 2016 to 2023, highlights significant advancements in various additive manufacturing techniques applied to smart textiles. The review emphasizes the importance of understanding 3D printing techniques such as FDM, SLS, DIW, and PolyJet, as their applicability for selecting the best approach to in-corporating advanced functionalities into smart textiles.
... Many inquiries have concentrated on enhancing the mechanical features of FDM polymers by optimizing 3D-printing conditions [43,44]. Nevertheless, few research works have concentrated on the fatigue performance of FDM ABS [16,[45][46][47][48][49][50]. Safai and Shanmugam expounded upon the fatigue behavior of 3D-printed polymers by providing a detailed overview. ...
This article explores the fatigue characteristics of acrylonitrile butadiene styrene (ABS) components fabricated using fused filament fabrication (FFF) additive manufacturing technology. ABS is frequently used as a polymeric thermoplastic material in open-source FFF machines for a variety of engineering applications. However, a comprehensive understanding of the mechanical properties and execution of FFF-processed ABS components is necessary. Currently, there is limited knowledge regarding the fatigue behavior of ABS components manufactured using FFF AM technology. The primary target of this study is to evaluate the results of part-build directions and build orientation angles on the tensile fatigue behavior exhibited by ABS material. To obtain this target, an empirical investigation was carried out to assess the influence of building angles and orientation on the fatigue characteristics of ABS components produced using FFF. The test samples were printed in three distinct directions, including Upright, On Edge, and Flat, and with varying orientation angles ([0°, 90°], [15°, 75°], [30°, 60°], [45°]), using a 50% filling density. The empirical data suggest that, at each printing angle, the On-Edge building orientation sample exhibited the most prolonged vibrational duration before fracturing. In this investigation, we found that the On-Edge printing direction significantly outperformed the other orientations in fatigue life under cyclic loading with 1592 loading cycles when printed with an orientation angle of 15°–75°. The number of loading cycles was 290 and 39 when printed with the same orientation angle for the Flat and Upright printing directions, respectively. This result underscores the importance of orientation in the mechanical performance of FFF-manufactured ABS materials. These findings enhance our comprehension of the influence exerted by building orientation and building angles on the fatigue properties of FFF-produced test samples. Moreover, the research outcomes supply informative perspectives on the selection of building direction and building orientation angles for the design of 3D-printed thermoplastic components intended for fatigue cyclic-loading applications.
... Once completed, the 3D model is split into hundreds or perhaps thousands of horizontal layers using specialized software. These layers are then fed to a 3D printer (which may interpret them differently depending on the model being used), which then uses a range of materials to print the object layer by layer, including plastics (ABS, PLA, PETG, etc.), resins, metals, and even ceramics (Hart, & Wetzel, 2017;Samiee & Azadi, 2018;Bardiya et al., 2021). Generally speaking, 3D printing and additive technology have become paradigm-shifting innovations. ...
The use of 3D printing technology has become more significant recently, especially in the area of developing new products. The process of creating a three-dimensional object or prototype using 3D printing technology is called layer-by-layer building. The present investigation has looked into the fatigue characteristics of 3D printed specimens. Acrylonitrile butadiene styrene (ABS) has been chosen as a study material due to its numerous applications. For the printing, three different raster angles 0°, 45°, and 90°, layer thickness of 0.255, infill density of 100%, and printing speed of 30 mm/s were used. The fused deposition modeling (FDM) method was employed to create the specimens. The dog bone-shaped object was made in accordance with ASTM D638 standard, and its mechanical properties were determined by a fatigue test. The fatigue test was carried out at tensile strengths of thirty, fifty, and seventy percent. The 3D-printed ABS samples at 45° and 90° raster angles show reduced fatigue cycles than the 0° raster angles for all loading percentages. The results indicated that the use of ABS material 3D printed at 45° and 90° raster angles might not be suitable for industrial environments.
... Recently, ABS plastics have been used to make kind of products viz. electronic housings, automobile parts, toys for children etc [70]. Furthermore, ABS polymers have good thermal stability, rigidity and lower thermal expansion making them durable and resistant to environmental stress conditions and chemical weathering in beach sand [71]. ...
... Recently, ABS plastics have been used to make kind of products viz. electronic housings, automobile parts, toys for children etc [70]. Furthermore, ABS polymers have good thermal stability, rigidity and lower thermal expansion making them durable and resistant to environmental stress conditions and chemical weathering in beach sand [71]. ...
... Li et al. observed print orientation dependency in single-edge notch tension (SENT) experiments for quasi-static fracture toughness in FDM printed materials Li et al. (2018). Hart and Wetzel also discovered print orientation dependency on layer relation to the crack tip in quasi-static fracture toughness values for single edge notch bend (SENB) tests Hart and Wetzel (2017). FDM printed polycarbonate parts have also demonstrated print orientation dependence for quasi-static fracture toughness for semi-circular bend experiments Bahrami et al. (2020). ...
This study examines the fracture behavior of two thermosetting polymer resins for additive manufacturing (AM) and specifically presents the role of print orientation on the quasi-static and dynamic fracture responses of DA-3 resin printed via digital light processing (DLP) and PM-EM828 resin printed via stereolithography (SLA). A unique long-bar apparatus is used to launch a striker at the opposite end of a notched and pre-cracked specimen to create a dominantly Mode-I (opening) fracture event. Digital image correlation (DIC) is used in conjunction with ultra-high-speed imaging to capture the evolving displacement fields ahead of the crack tip. The elastodynamic solution for a stationary crack is used to determine the critical stress intensity factor (SIF), and the asymptotic steady-state dynamic crack solution is used to examine propagation behavior. These results are compared to quasi-static experiments of the same material and similar geometries on a standard load frame. Both DA-3 and PM-EM828 exhibited higher quasi-static fracture toughness values than critical dynamic stress intensity values, although the PM-EM828 demonstrated less rate dependence on fracture toughness than DA-3. Overprinting the last two layers of the weakest DA-3 orientation proved to enhance isotropy of DLP 3-dimensional (3D) printed DA-3 plaques while PM-EM828 plaques 3D printed by SLA did not show significant anisotropy.
... 18 In recent years, researchers have focused on the fracture behavior of FDM parts with a pre-existing crack under different loading conditions. For instance, Hart et al. 19 investigated the influence of layer orientation on the mode I fracture behavior of FDM-ABS specimens. The results confirmed that the specimens printed horizontally had higher fracture resistance compared with those printed vertically. ...
Fused deposition modeling (FDM) is a material extrusion technique that works by extruding molten filament on a heated platform. In this method, several manufacturing parameters are engaged which affect the mechanical performance of printed parts. In this study, the effects of nozzle diameter on tensile (under two loading rates) and mixed‐mode I/II fracture behavior of printed specimens were examined. The obtained results revealed that testing speed had a minor effect on basic mechanical properties. For instance, ultimate tensile strengths of tensile specimens printed with 1 mm nozzle diameter were 32.56 and 39.71 MPa for test speeds of 1 and 5 mm/min, respectively. Higher nozzle diameters resulted in higher mechanical properties and fracture resistance (e.g., specimens printed with 45/−45° raster angle with 0.4 and 1 mm nozzle diameters indicated fracture loads of 4520 and 5071 N, respectively). Besides, fracture loads were predicted through the equivalent material concept coupled with J‐integral method.
... The value of Y I for the SCB specimen solely relies on its geometry, while K I varies with changes in the applied load. Therefore, to determine the fracture toughness of the photopolymer when printed in various orientations, it is essential to insert the respective applied load and Y I values into Equation (8). ...
Herein, we conducted tensile and fracture tests on a photopolymer produced with a stereolithography apparatus (SLA), utilizing dog‐bone and semi‐circular bending specimens fabricated in five different orientations. The analysis revealed a direct linear correlation between the tensile strength and printing orientation, highlighting a decrease in tensile strength with an increase in orientation angle. Young's modulus of the printed material remained insensitive to the printing orientation. Conversely, fracture toughness demonstrated a distinct cubic polynomial relationship with the printing orientation. The equivalent material concept in conjunction with the maximum tangential stress criterion was used to predict the fracture behavior of SLA printed polymer. This research sheds light on the significant effect of printing orientation on the mechanical properties of SLA printed materials, offering pivotal insights for optimizing SLA printing across various applications and catalyzing progress in this research field.
... This result may be associated with the fact that during annealing, which maintains the parts at a temperature above the Tg of the polymer, the greater mobility of the macromolecules allows for better intertwining of the polymer chains, improving adhesion between the deposited filaments (Seppala et al, 2017). Another possibility is the change suffered in the empty spaces configuration, which can coalesce and form structures of lower stress concentration, or even facilitate contact between the layers, as observed by Hart et al (2017). Another possibility of increasing the mechanical properties comes from the crystallization process itself, since the crystals act as barriers to the stretching of the amorphous chains, which is the initial mechanism of the elastoplastic deformation observed in thermoplastic polymers (Callister, 2006). ...
... Thus, the fracture behavior of the FDM samples under different loading conditions gained more attention from researchers. By employing Single Edge Notch Bending (SENB) specimens, Hart et al. 26 investigated the impact of layer orientation on the fracture toughness of FDM-ABS parts. In their study, samples that were oriented horizontally had higher fracture loads than samples that were oriented vertically. ...
Additive Manufacturing (AM) processes are known as revolutionary manufacturing processes that fabricate a part using a 3D model layer upon layer. These techniques gained more attention from various industries due to their advantages like low waste material. Also, these processes can produce any part with high degrees of complexity in a short period of time. The Fused Deposition Modeling (FDM) process is a material extrusion-based technique which works by extruding a fine molten polymeric filament through a heated nozzle on the heated platform named printer bed. In this method, some important manufacturing parameters play a crucial role in controlling the mechanical properties and quality of the final fabricated part. However, all printed specimens through the FDM process should be tested based on the standards under some critical circumstances. Thus, in the current research paper, five and three test speeds are considered in tensile and fracture testing procedures, respectively to evaluate how these speeds can affect the mechanical and mode I fracture properties. Also, as the FDM specimens present elastic–plastic behavior, the critical value of J-integral is assumed as a fracture assessment and calculated from the finite element analysis. Among the mechanical properties, ultimate tensile strength is affected significantly by the test speed. For instance, the ultimate tensile strength of FDM specimens is 39.02, 38.58, 42.33, 48.09, and 52.11 for test speeds of 2, 4, 6, 8, and 10 mm/min, respectively. But vice-versa results are detected for the mode I fracture behavior and corresponding values of J for the FDM-PLA specimens. Finally, experimental and numerical results together with comprehensive discussions about the considered speeds and obtained results are reported.
... The additive nature of the MEX process results in intralayer and interlayer areas that are particularly weak and susceptible to fracture as represented in the diagram in (Ahn et al., 2002;Koch et al., 2017;Young et al., 2018;Zaldivar et al., 2017). Hart and Wetzel (2017) showed that intralayer fracture resistance can be increased by an order of magnitude compared to interlayer fracture simply by alternating raster orientations 90 degrees from layer to layer. Conversely, interlayer fracture properties cannot be improved using simple geometric approaches, leading many researchers to study interlayer bond strength and the related concept of interlayer fracture toughness, G c , in a variety of MEX build materials (Fonseca et al., 2019;Khan et al., 2021;Khudiakova et al., 2019;Gao et al., 2021). ...
Parts produced using material extrusion (MEX), a common additive manufacturing method, are often limited to non-structural applications due to sub-optimal mechanical properties, including poor interlayer fracture toughness, Gc. Gc of MEX parts depends on process parameters, but the complex relationships between process parameters and Gc are not well understood. This paper describes the use of a machine learning (ML) method using Forests with Uncertainty Estimates for Learning Sequentially (FUELS) to study the effect of five process parameters on the Gc of MEX parts. Training data for the FUELS model is collected using a modified double cantilever beam (MDCB) test, and Gc is calculated using a classical beam theory approach. The FUELS method provides guided testing by suggesting additional parameter combinations from high-uncertainty regions of the parameter space. After sequentially testing a total of 2.9% of the 2205 possible parameter combinations, there was minimal change in the non-dimensional model error, and training was concluded. Gc values collected from testing ranged 0.056 kJ/m² to 1.774 kJ/m². The resulting parameter space was examined to better understand how Gc evolves with changing process parameters. Among other results, extrusion temperature was shown to have a greater effect on Gc at higher print speeds. Overall, the FUELS method, paired with accelerated experimental testing, provides a useful means of quickly exploring the large MEX parameter space to establish relationships among process parameters and Gc. The methods of this study can serve as a blueprint for other studies with large parameter spaces, not just in MEX but in other manufacturing processes.
... During the printing process, once the defects mentioned above appear, it is difficult to eliminate by adjusting the printing parameters. When these defects accumulate to a certain extent, the printed part will face some serious problems, such as low strength, low toughness, and rough surfaces [8,9]. Therefore, fuses in printed parts often need to be kept in a tight fit to improve their mechanical properties [10]. ...
Fused deposition modeling comes with many conveniences for the manufacturing industry, but many defects tend to appear in actual production due to the problems of the FDM mechanism itself. Although some deep learning-based object detection models show excellent performance in detecting defects in the additive manufacturing process, their detection efficiency is relatively low, and they are prone to drawbacks in the face of large numbers of defects. In this paper, an improved model based on the YOLO v4 network structure is developed. We lightweight the model and modify its loss function to achieve better performance. Experimental results show that the improved model, MobileNetV2-YOLO v4, achieves a mAP of 98.96% and an FPS of 50.8 after training, which obtains higher detection accuracy and faster detection speed than the original YOLO v4 algorithm model. Through testing, this improved model can accurately identify the location and information of target defects, which has great potential for real-time detection in the additive manufacturing process.
... This deformation is theorized to be attributed to the lower print density and therefore increased instance of voids within the structure, which reduce the thermo-structural stability of the part. Increased instance of voids also drastically reduces the Izod impact strength of the parts since they act as stress concentrators [20][21][22] . For the v f = 94% 17-94 samples, the specimens displayed no significant warping at any annealing temperature; however slight upward (in z-direction) deformation of 0.23 mm relative to the as-printed print face was observed at 155 °C for 8 h samples, and slightly higher deformation of 1.03 mm was observed for samples annealed at 175 °C for 8 h. ...
Thermoplastic parts manufactured via fused filament fabrication (FFF) have limited strength and toughness compared to other types of polymer additive and subtractive manufacturing. Low strength results from poor interlayer adhesion, making FFF parts not suitable for most engineering applications. Post processing solutions, such as annealing, enable healing of these interlayers, thus approaching injection molded parts. Prior work demonstrated a core–shell polycarbonate (PC)—acrylonitrile butadiene styrene (ABS) structured dual material filament to provide thermo-structural stability during annealing of the ABS component; however, annealing was limited to relatively low temperatures (135 °C) and required long annealing times (72 h). In the current work, a PC copolymer with a higher glass transition temperature (173 °C) than conventional PC is processed along with an extrusion-grade ABS into a PC-ABS core–shell filament. This improved dual material filament was printed, annealed, and evaluated via Izod impact testing, ultimately yielding 83% of bulk annealed ABS z-direction strength at an accelerated annealing time (8 h) and higher annealing temperature (155—175 °C). A demonstration part is printed with the dual material filament and annealed at 155 °C for 8 h, resulting in excellent dimensional accuracy, and a ductile failure at 73% higher ultimate load compared to the brittle failure of an as-printed part. This work highlights that material selection and design of a bicomponent filament geometry can lead to parts printed with FFF, with increased strength compared to other post-processing techniques at reduced processing times.
... Zhang et al. studied the fracture behavior of a glass-fiber-reinforced polymer gasket under tensile stress at various temperatures [20]. Compared with other techniques, Hart et al. have shown that the phenomenon of crack propagation in polymer structures obtained by FDM is complex due to their microstructures, which are highly dependent on various printing parameters [21]. ...
This article investigates the impact of raster width on crack propagation resistance in structures manufactured using the FDM (Fused Deposition Modeling) additive manufacturing process. This process involves a large number of variables to be controlled, which influence the mechanical properties and quality of the parts produced. During layer-by-layer printing, the filaments making up each layer fuse together on adjacent and overlapping sides. This fusion occurs at the contact surfaces, which depend mainly on the raster's width and the deposited filaments' length. The quality of this fusion plays a crucial role in the resistance to crack propagation, both between filaments and between layers. Therefore, this article aims to examine how raster width affects resistance to crack propagation in FDM structures. In this study, we developed two approaches; one is experimental based on CT (Compact Tension) specimens to assess the fracture toughness of poly-lactic acid (PLA)-based polymers using the theoretical approach of the J integral. To do so, we determined the strength curves (J-∆a) and deduced the J IC parameter for different raster widths (l = 0.42 mm, l = 0.56 mm and l = 0.68 mm). To better understand the behavior of contact zones between filaments during fracture, we developed a simplified numerical approach. The numerical results obtained were analyzed and discussed on the basis of observations of the fracture facies of CT specimens.
... Although 3D-printing technology has been enhanced substantially in recent years, there is no specific standard for evaluating the fracture toughness of 3D-printed parts. Hence, the standards which are already available for plastic parts [22] (for example, compact tension (CT) [23][24][25], single-edge cracked [26,27], three-point bending [28,29], and Double Cantilever Beam (DCB) [30-32]) have been used for SFRP and cFRP composites as well. García-Guzman et al. [33] experimentally and analytically studied the fracture behavior of adhesively bonded DCB composite specimens made of Glass Fiber reinforced PolyAmide (GF/PA), with both trapezoidal and flat interface patterns. ...
It is well known that the use of continuous reinforcing fibers can largely improve the typical low in-plane mechanical properties of 3D-printed parts. However, there is very limited research on the characterization of the interlaminar fracture toughness of 3D-printed composites. In this study, we investigated the feasibility of determining the mode I interlaminar fracture toughness of 3D-printed cFRP composites with multidirectional interfaces. First, elastic calculations and different FE simulations of Double Cantilever Beam (DCB) specimens (using cohesive elements for the delamination, in addition to an intralaminar ply failure criterion) were carried out to choose the best interface orientations and laminate configurations. The objective was to ensure a smooth and stable propagation of the interlaminar crack, while preventing asymmetrical delamination growth and plane migration, also known as crack jumping. Then, the best three specimen configurations were manufactured and tested experimentally to validate the simulation methodology. The experimental results confirmed that, with the appropriate stacking sequence for the specimen arms, it is possible to characterize the interlaminar fracture toughness in multidirectional 3D-printed composites under mode I. The experimental results also show that both initiation and propagation values of the mode I fracture toughness depend on the interface angles, although a clear tendency could not be established.
... As it appears in some AM processes, the printed parts possess anisotropic characteristics, meanwhile, the mechanical properties like tensile strength vary with several printing parameters such as printing angle and orientation on the build platform [74][75][76][77][78][79][80][81][82]. According to the AM technique and 3D printing machine, some researchers attempted to develop a constitutive model to predict the structural response of the printed parts against the input force or moment. ...
The unique design freedom offered by additive manufacturing (AM) technologies enables engineers to develop more innovative products with relatively lower costs within a shorter period of processing time in comparison with conventional manufacturing methods. On the other hand, the unique capabilities of AM have created a platform for researchers to combine several engineering methods with the new manufacturing technique to grow industrial applications as well as resolve the existing issues with AM processes. Understanding the research values that AM offers academic environments, this paper performs a systematic survey on AM-related research topics in the fields of mechanical engineering and materials science that have attracted much attention from research teams over the last few years. These topics, namely process modelling in AM, innovative research in AM, generative design by AM, material characterisation in AM processes, and finally, design for additive manufacturing (DfAM), are notably investigated through this study.
Combining characteristics of two different materials offer improved performance in numerous application. Innovative material
(IM) is one such heterogenous material fabricated through additive manufacturing (AM) technique by depositing poly lactic
acid (PLA: M-1) and ceramic PLA (M-2) an alternate layer. Lightweight, heat resistance, and improved strength obtained
from combining attributes of M-1 and M-2 are effectively superimposed in IM. Single edge notch bend (SENB) test is used to
study fracture behaviour of considered materials and assess its mode I fracture toughness (KIC) by means of experimentation
and numerical simulation. Experimental values of KIC are obtained as 5.72 MPa √m, 6.8 MPa √m, and 11.54 MPa √m for
M-1, M-2 and IM. Strong correlation between experimental and simulation indicates that IM has a stronger fracture resistance
than M-1 and M-2, suggesting that it could replace metals in light-weight application. This encourages effective use of IM
structures in aerospace, automotive, and architectural industries where fracture resistance is crucial.
Hydrogen is gaining attention as a fossil fuel alternative due to its potential to meet global energy demands. Producing hydrogen from water splitting is promising as a clean and sustainable fuel pathway. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are crucial in electrocatalytic water splitting for energy conversion and storage. However, water electrolysis faces challenges in cost, efficiency, and scalability. Alternative transition metal electrocatalysts and emerging 2D materials advance electrolysis research, though transitioning from academia to industry remains challenging. The introduction of 3D‐printing technologies has revolutionized electrode fabrication for HER and OER. This review explores integrating 3D‐printing technologies and surface functionalization with non‐noble metal‐based electrocatalysts and emerging 2D materials. It focuses on surface‐functionalized 3D‐printed electrodes using technologies like selective laser melting, stereolithography, and fused deposition modeling with non‐noble metal electrocatalysts such as transition metal oxides, hydroxides, and emerging 2D materials like transition metal carbide/nitride (MXenes) and transition metal dichalcogenides (TMDCs). The review highlights the opportunities and challenges in scalable fabrication, long‐term durability, and cost‐efficiency for practical implementation. Future research directions include exploring new materials for 3D printing and alternative electrocatalysts alongside leveraging theoretical and machine‐learning approaches to accelerate the development of competitive materials for water electrolysis.
The emergence of additive manufacturing has enabled scientists to efficiently construct complex geometries, facilitating the development of novel, high-impact energy-absorbing structures suitable for a wide range of industrial applications. The present study conducted flexural and impact test to quantitatively assess the energy absorption capabilities of polymer composites fabricated through fused filament fabrication. Specifically, the polymer composites investigated were multi-walled carbon nanotubes reinforced poly-lactic acid, carbon fibre reinforced poly-ethylene terephthalate glycol, and carbon fibre reinforced poly-lactic acid. The investigation also examined the influence of different infill patterns and nozzle hole diameters on the polymer composites. The investigation depicts that by altering the process parameters, the flexural strength is improved from 21.079 MPa to 70.653 MPa by 235.18%. The experimental study of impact specimens utilising the Izod impact test demonstrates that the rectilinear infill pattern and a nozzle hole diameter of 0.6 mm result in the highest energy absorption of 37.76 kJ/m2 for carbon fibre reinforced poly-lactic acid. The study revealed that the energy absorption of the specimens was significantly influenced by both the independent and interaction effects of process variables. The application of the fused filament fabrication demonstrates an improved energy absorption, making it suitable for manufacturing of vehicle and aircraft components.
The FDM (Fused Deposition Modelling) additive manufacturing process is characterised by a large number of process variables that determine the mechanical properties and quality of the manufactured parts. When printing layer by layer, the filaments constituting the layer are welded on the one hand between them in the same layer and on the other hand between the superimposed layers, this welding develops on the contact surfaces (raster width) along the deposited filaments. The quality of this welding determines the resistance to crack propagation between filaments and between layers. This article aims to study the effect of the width of the raster on the resistance to crack propagation in a structure obtained by FDM.We have developed an experimental approach from CT specimens to determine the tensile strength of polylactic acid (PLA) polymers, considering the J-Integral method. And given the complexity of the problem, three cases of raster width (l=0.42 mm, l=0.56 mm and l=0.68 mm) have been treated.According to the results obtained (J, ∆a), the resistance to crack propagation in the parts printed by FDM seems to be better when the width of the filament is small. Indeed, the energy necessary to break the specimen is relatively greater than in the case of a larger width. This finding was confirmed by comparing the values of J for a given advancement of the crack for the three cases studied.In order to present an exhaustive study, we focused on the effect of raster widths (including 0.42 mm, 0.56 mm to 0.68 mm) on the crack propagation of printed PLA. This study is in progress for other printing parameters. To highlight the cracking mechanisms, microscopic observations will be developed in greater depth at the SEM.Our analysis can be used as decision support in the design of FDM parts. In effect, we can choose the raster width that would provide the resistance to crack propagation desired for a functional part.In this article, we analysed the damage mechanism of CT specimens printed by FDM. This subject represents a new direction for many lines of research. For our study, we used the J-Integral theoretical approach to study the fracture behaviour of these parts by determining the resistance curves (J-∆a).
Considering the industrial requirements on the mechanical performances requested in the printed parts, many research axes have been developed. Among these requirements, the resistance to breakage of this type of structures printed by FDM is very complex and little developed. The objective of this study is to analyze and understand the effect of raster widths on the mechanical performance and crack propagation in an ABS (Acrylonitrile–Butadiene–Styrene) sample obtained by FDM (Fused Deposition Modeling). A numerical approach has been developed to link this printing parameter (the raster width) to the crack propagation phenomenon. And more particularly our study was oriented towards the analysis of the cohesion between filaments, for that, we treated only two cases of width of the raster (l = 0.42 and l = 0.56 mm). In order to analyze the results obtained from the concepts of the energetic theory of the rupture.KeywordsFDMRaster widthABSCT specimenCrackNumerical simulation
Acrylonitrile butadiene styrene (ABS) is a commonly used copolymer. It is widely employed, especially in additive manufacturing (AM), a newly developed and open-ended production method. It can be used in medical applications due to its biocompatible behaviour and performance characteristics. Though there are a few disadvantages of the AM, improving the sample's mechanical properties are possible by applying pre-processing to the filament (dehumidification) or choosing the correct printing parameters. Nevertheless, surface quality is limited regardless of the mechanical properties and printing parameters. For this reason, finishing, called post-processing, is often preferred. ABS post-process application is made with an acetone vapour atmosphere. However, this application is a chemical process. This chemical process could change the properties of the ABS sample. This paper investigates the effect of post-processing on the ABS sample. According to reference samples, the change in porosity values was measured from 30 to 60%. In addition, as the post-processing time increased, the hue of the samples shifted from yellow to blue and from dark to light. Further, increased acetone vapour exposure decreased the bending and tensile test results. The impact of acetone vapour exposure on the toughness of ABS polymer has yielded conflicting results.
The recent creation and growth of desktop three-dimensional (3D) printing has led to a new way of building objects. In the manufacture of pieces using Open-Source 3D printing it is very common to use a range of infill patterns and densities with the aim of reducing printing time and material consumption. However, it is not well understood how these factors influence the characteristics of the pieces obtained. Due to the differences with FDM technology, it is necessary to evaluate the strength of the pieces manufactured with this technology. In this work, the influence of two controllable variables, such as pattern and density of the infill has been evaluated. A series of test pieces with different density characteristics and infill patterns were produced using an open-source 3D printer. The results obtained show that the influence of the different printing patterns causes a variation of less than 5% in maximum tensile strength, although the behavior is similar. The change in infill density determines mainly the tensile strength. The combination of a rectilinear pattern in a 100% infill shows the higher tensile strength, with a value of 36.4 Mpa, with a difference of less than 1% from raw ABS material.
While fused deposition modelling (FDM) is one of the most used additive manufacturing (AM) techniques today due to its ability to manufacture very complex geometries, the major research issues have been to balance ability to produce aesthetically appealing looking products with functionality. In this study, five important process parameters such as layer thickness, part orientation, raster angle, raster width, and air gap have been considered to study their effects on tensile strength of test specimen, using design of experiment (DOE). Using group method of data handling (GMDH), mathematical models relating the response with the process parameters have been developed. Using differential evolution (DE), optimal process parameters have been found to achieve good strength simultaneously for the response. The optimization of the mathematical model realized results in maximized tensile strength. Consequently, the additive manufacturing part produced is improved by optimizing the process parameters. The predicted models obtained show good correlation with the measured values and can be used to generalize prediction for process conditions outside the current study. Results obtained are very promising and hence the approach presented in this paper has practical applications for design and manufacture of parts using additive manufacturing technologies.
Accessible via: https://momrg.cecs.ucf.edu/wp-content/uploads/2019/05/Torres-et-al.-2016-RPJ.pdf
Purpose
This paper aims to present the influences of several production variables on the mechanical properties of specimens manufactured using fused deposition modeling (FDM) with polylactic acid (PLA) as a media and relate the practical and experimental implications of these as related to stiffness, strength, ductility and generalized loading.
Design/methodology/approach
A two-factor-level Taguchi test matrix was defined to allow streamlined mechanical testing of several different fabrication settings using a reduced array of experiments. Specimens were manufactured and tested according to ASTM E8/D638 and E399/D5045 standards for tensile and fracture testing. After initial analysis of mechanical properties derived from mechanical tests, analysis of variance was used to infer optimized production variables for general use and for application/load-specific instances.
Findings
Production variables are determined to yield optimized mechanical properties under tensile and fracture-type loading as related to orientation of loading and fabrication.
Practical implications
The relation of production variables and their interactions and the manner in which they influence mechanical properties provide insight to the feasibility of using FDM for rapid manufacturing of components for experimental, commercial or consumer-level use.
Originality/value
This paper is the first report of research on the characterization of the mechanical properties of PLA coupons manufactured using FDM by the Taguchi method. The investigation is relevant both in commercial and consumer-level aspects, given both the currently increasing utilization of 3D printers for component production and the viability of PLA as a renewable, biocompatible material for use in structural applications.
The successful invention of self-healing polymer composites a decade ago necessitated a methodology to quantify the ability of the material to heal and recover structural properties following damage. Healing efficiency was defined as the ratio of healed to virgin fracture toughness, η = KIChealed/KICvirgin. Early work took advantage of the crack length independence offered by a tapered double-cantilever beam (TDCB) fracture geometry to simplify calculation of healing efficiency to the ratio of healed to virgin critical loads, η = PChealed/PCvirgin. The current work investigates the application of the TDCB geometry and three common geometries utilized in the broader fracture literature (the compact tension (CT), single-edge notch bend (SENB), and single-edge notch tension (SENT) geometries) to the measurement of healing efficiency. While the TDCB geometry simplifies the calculation of healing efficiency because the crack lengths do not need to be accounted for, it is shown that if the virgin and healed crack lengths are not accurately accounted when using the CT, SENB, and SENT geometries, errors in calculated healing efficiency can be several hundred per cent. The TDCB geometry is reviewed at length, including the underlying theory and experimental calibration and validation of TDCB geometry.
Fused deposition modelling (FDM) is gaining distinct advantage in manufacturing industries because of its ability to manufacture parts with complex shapes without any tooling requirement and human interface. The properties of FDM built parts exhibit high dependence on process parameters and can be improved by setting parameters at suitable levels. Anisotropic and brittle nature of build part makes it important to study the effect of process parameters to the resistance to compressive loading for enhancing service life of functional parts. Hence, the present work focuses on extensive study to understand the effect of five important parameters such as layer thickness, part build orientation, raster angle, raster width and air gap on the compressive stress of test specimen. The study not only provides insight into complex dependency of compressive stress on process parameters but also develops a statistically validated predictive equation. The equation is used to find optimal parameter setting through quantum-behaved particle swarm optimization (QPSO). As FDM process is a highly complex one and process parameters influence the responses in a non linear manner, compressive stress is predicted using artificial neural network (ANN) and is compared with predictive equation.
Bone and nacre are the most-known biological hard tissues to materials researchers. Although highly mineralized, both bone and nacre are amazingly tough and exhibit remarkable inelasticity, properties that are still beyond the reach of many modern ceramic materials. Very interestingly, the two hard tissues seem to have adopted totally different structural strategies for achieving mechanical robustness. Starting from a true nanocomposite of the mineralized collagen fibril and following up to seven levels of hierarchical organization, bone is built on a structure with extreme complexity. In contrast, nacre possesses a structure of surprising simplicity. Polygonal mineral tablets of micrometer size are carefully cemented together into a macroscopic wonder. A comparative analysis of the structure-property relations in bone and nacre helps us to unveil the underlying mechanisms of this puzzling phenomenon. In this review, we critically compare the various levels of structures and their mechanical contributions...
In literature several studies have been performed to analyze the surface finish of rapid prototyped parts. These researches have been mainly aimed to the optimal build direction of prototypes to obtain the best possible surface finish on specific surfaces. Very diffuse technologies that suffers considerably of low surface quality are Fused Deposition Modeling (FDM) and extrusion based Rapid Prototyping machines in general. Hand finishing for even the most basic levels of part quality are often required by the customers, forcing the geometrical features of the prototypes to be controlled by the skill level of the operator. This study completes past researches performed by the authors on tensile and flexural properties of chemical dipped specimens after immersion in a dimethyl ketone-water solution. The authors aim to gain a more in-depth knowledge of this process, by analyzing and comparing the compressive properties of finished and non-finished FDM parts through the use of an experimental approach, totalizing about 100 tests.
A line integral is exhibited which has the same value for all paths surrounding the tip of a notch in the two-dimensional strain field of an elastic or deformation-type elastic-plastic material. Appropriate integration path choices serve both to relate the integral to the near tip deformations and, in many cases, to permit its direct evaluation. This averaged measure of the near tip field leads to approximate solutions for several strain-concentration problems. Contained perfectly plastic deformation near a crack tip is analyzed for the plane-strain case with the aid of the slip-line theory. Near tip stresses are shown to be significantly elevated by hydrostatic tension, and a strain singularity results varying inversely with distance from the tip in centered fan regions above and below the tip. Approximate estimates are given for the strain intensity, plastic zone size, and crack tip opening displacement, and the important role of large geometry changes in crack blunting is noted. Another application leads to a general solution for crack tip separations in the Barenblatt-Dugdale crack model. A proof follows on the equivalence of the Griffith energy balance and cohesive force theories of elastic brittle fracture, and hardening behavior is included in a model for plane-stress yielding. A final application leads to approximate estimates of strain concentrations at smooth-ended notch tips in elastic and elastic-plastic materials.
Properties of the organic matrix of bone as well as its function in the microstructure could be the key to the remarkable mechanical properties of bone. Previously, it was found that on the molecular level, calcium-mediated sacrificial bonds increased stiffness and enhanced energy dissipation in bone constituent molecules. Here we present evidence for how this sacrificial bond and hidden length mechanism contributes to the mechanical properties of the bone composite, by investigating the nanoscale arrangement of the bone constituents and their interactions. We find evidence that bone consists of mineralized collagen fibrils and a non-fibrillar organic matrix, which acts as a 'glue' that holds the mineralized fibrils together. We believe that this glue may resist the separation of mineralized collagen fibrils. As in the case of the sacrificial bonds in single molecules, the effectiveness of this mechanism increases with the presence of Ca2+ ions.
Bone, with a hierarchical structure that spans from the nano-scale to the macro-scale and a composite design composed of nano-sized mineral crystals embedded in an organic matrix, has been shown to have several toughening mechanisms that increases its toughness. These mechanisms can stop, slow, or deflect crack propagation and cause bone to have a moderate amount of apparent plastic deformation before fracture. In addition, bone contains a high volumetric percentage of organics and water that makes it behave nonlinearly before fracture. Many researchers used strength or critical stress intensity factor (fracture toughness) to characterize the mechanical property of bone. However, these parameters do not account for the energy spent in plastic deformation before bone fracture. To accurately describe the mechanical characteristics of bone, we applied elastic-plastic fracture mechanics to study bone's fracture toughness. The J integral, a parameter that estimates both the energies consumed in the elastic and plastic deformations, was used to quantify the total energy spent before bone fracture. Twenty cortical bone specimens were cut from the mid-diaphysis of bovine femurs. Ten of them were prepared to undergo transverse fracture and the other 10 were prepared to undergo longitudinal fracture. The specimens were prepared following the apparatus suggested in ASTM E1820 and tested in distilled water at 37 degrees C. The average J integral of the transverse-fractured specimens was found to be 6.6 kPa m, which is 187% greater than that of longitudinal-fractured specimens (2.3 kPa m). The energy spent in the plastic deformation of the longitudinal-fractured and transverse-fractured bovine specimens was found to be 3.6-4.1 times the energy spent in the elastic deformation. This study shows that the toughness of bone estimated using the J integral is much greater than the toughness measured using the critical stress intensity factor. We suggest that the J integral method is a better technique in estimating the toughness of bone.
In this work the effect of strain rate on the tensile strength of fused deposition modeling parts built with Acrylonitrile-butadiene-styrene (ABS) and ABS plus material is presented. ASTM D638-02a specimens were built with ABS and ABS plus and they were tested on a Schenck Trebel Co. tensile test machine at three different test speeds, equal, lower, and higher to the test speed required by the ASTM D638-02a standard. The experimental tensile strength results were compared and evaluated. The fracture surfaces of selected specimens were examined with a scanning electron microscope, to determine failure mode of the filament strands. It was found that, as the test speed increases, specimens develop higher tensile strength and have higher elastic modulus. Specimens tested in the highest speed of the experiment had on average about 10% higher elastic modulus and developed on average about 11% higher tensile strength.
The aim of the present study is to utilize fractographic methods employing scanning electron microscope (SEM) images to investigate the effects of build direction and orientation on the mechanical response and failure mechanism for Acrylonitrile–Butadiene–Styrene (ABS) specimens fabricated by fused deposited modeling (FDM). The material characterized here is ABS-M30 manufactured by Stratasys, Inc. Measurements of tensile strength, elongation-at-break and tensile modulus measurements along with the failure surfaces were characterized on a range of specimens at different build direction and raster orientation: ±45°, 0°, 0/90°, and 90°. The analysis of mechanical testing of the tensile specimens until failure will contribute to advances in creating stronger and more robust structure for various applications. Parameters, such as build direction and raster orientation, can be interdependent and exhibit varying effects on the properties of the ABS specimens. The ABS-M30 specimens were found to exhibit anisotropy in the mechanical response when exposed to axial tensile loading. The stress-strain data was characterized by a monotonic increase with an abrupt failure signifying brittle fracture. In certain combinations of build direction and raster orientation tensile failure was preceded by slight softening. The tensile strength and modulus, and elongation-at-break were found to be highly dependent upon the raster orientation and build direction. The relationship between the mechanical properties and failure was established by fractographic analysis. The fractographic analysis offers insight and provides valuable experimental data for the purpose of building structures in orientations tailored to their exemplified strength. For instance, specimens loaded such that bonds between adjacent rasters are the primary load bearing mechanism offer the least significant failure resistance. Other examples are shown where artifacts of the FDM fabrication process act to enhance tensile strength when configured properly with respect to the load. The results highlighted in this study are fundamental to the development of optimal design of complex ultra-light structure weight with increased structural efficiency. The study also presents a systematic scheme employing analogs to traditional fiber-reinforced polymer composites for the designation of build orientation and raster orientation parameters.
We describe an experimental approach for characterizing the local mechanical behavior of acrylonitrile butadiene styrene (ABS) structures processed through fused deposition modeling. ABS test specimens processed in various build orientations were subject to multiscale mechanical tests as well as local morphology and chemical analyses. Instrumented indentation, local dynamic mechanical analysis, and atomic force microscopy tests were used to explore the mechanical behavior and morphology of build surfaces and weld interfaces. An interfacial stiffening effect was found for the majority of the specimens tested, with up to a 40% increase in the indentation elastic modulus measured with respect to the build surfaces. Raman spectroscopy mapping of the interfacial areas revealed 30% less butadiene/styrene and butadiene/acrylonitrile ratios with respect to analysis of the build surfaces. The results provide insight into the multiscale behavior of additive manufactured structures and offer the potential to guide processing-structure-property understanding of these materials.
Purpose
– This paper aims to define the effect of specimen mesostructure on the monotonic tensile behavior and tensile-fatigue life of layered acrylonitrile butadiene styrene (ABS) components fabricated by fused deposition modeling (FDM).
Design/methodology/approach
– Tensile tests were performed on FDM dogbone specimens with four different raster orientations according to ASTM standard D638-03. Resulting ultimate tensile stresses (UTS) for each raster orientation were used to compute the maximum stress for fatigue testing, i.e. 90, 75, 60 and 50 or 45 per cent nominal values of the UTS. Multiple specimens were subjected to tension – tension fatigue cycling with stress ratio of R = 0.10 in accordance with ASTM standard D7791-12.
Findings
– Both tensile strength and fatigue performance exhibited anisotropic behavior. The longitudinal (0°) and default (+45/−45°) raster orientations performed significantly better than the diagonal (45°) or transverse (90°) orientations in regards to fatigue life, as displayed in the resulting Wohler curves.
Practical implications
– Raster orientation has a significant effect on the fatigue performance of FDM ABS components. Aligning FDM fibers along the axis of the applied stress provides improved fatigue life. If the direction of applied stresses is not expected to be constant in given application, the default raster orientation is recommended.
Originality/value
– This project provides knowledge to the limited work published on the fatigue performance of FDM ABS components. It provides S-N fatigue life results that can serve as a foundation for future work, combining experimental investigations with theoretical principles and the statistical analysis of data.
Purpose
– The purpose of this paper is to systematically and critically review the literature related to process design and modeling of fused deposition modeling (FDM) and similar extrusion-based additive manufacturing (AM) or rapid prototyping processes.
Design/methodology/approach
– A systematic review of the literature focusing on process design and mathematical process modeling was carried out.
Findings
– FDM and similar processes are among the most widely used rapid prototyping processes with growing application in finished part manufacturing. Key elements of the typical processes, including the material feed mechanism, liquefier and print nozzle; the build surface and environment; and approaches to part finishing are described. Approaches to estimating the motor torque and power required to achieve a desired filament feed rate are presented. Models of required heat flux, shear on the melt and pressure drop in the liquefier are reviewed. On leaving the print nozzle, die swelling and bead cooling are considered. Approaches to modeling the spread of a deposited road of material and the bonding of polymer roads to one another are also reviewed.
Originality/value
– To date, no other systematic review of process design and modeling research related to melt extrusion AM has been published. Understanding and improving process models will be key to improving system process controls, as well as enabling the development of advanced engineering material feedstocks for FDM processes.
Purpose – This paper aims to provide a review of available published literature in which nanostructures are incorporated into AM printing media as an attempt to improve the properties of the final printed part. The purpose of this article is to summarize the research done to date, to highlight successes in the field, and to identify opportunities that the union of AM and nanotechnology could bring to science and technology. Design/methodology/approach – Research in which metal, ceramic, and carbon nanomaterials have been incorporated into AM technologies such as stereolithography, laser sintering, fused filament fabrication, and three-dimensional printing is presented. The results of the addition of nanomaterials into these AM processes are reviewed. Findings – The addition of nanostructured materials into the printing media for additive manufacturing affects significantly the properties of the final parts. Challenges in the application of nanomaterials to additive manufacturing are nevertheless numerous. Research limitations/implications – Each of the AM methods described in this review has its own inherent limitations when nanoparticles are applied with the respective printing media. Overcoming these design boundaries may require the development of new instrumentation for successful AM with nanomaterials. Originality/value – This review shows that there are many opportunities in the marriage of AM and nanotechnology. Promising results have been published in the application of nanomaterials and AM, yet significant work remains to fully harness their inherent potential. This paper serves the purpose to researchers to explore new nanomaterials-based composites for additive manufacturing.
A mixed mode I/II fracture criterion applicable to cracks oriented both along and across the fibres in wood is derived within the framework of linear elastic fracture mechanics. The use of a common fracture criterion for both types of cracks is made possible by the fact that cracks in wood generally propagate along the fibres, irrespective of both the original crack orientation and the degree of mode mixity. The derived criterion is simple, and contains a single material dependent fracture parameter. The applicability of the fracture criterion to spruce (Picea abies) is experimentally validated in part two of the paper.
The toughness of three high-thermal-resistant ABSs and the associated deformation behavior were studied. Matrix deformation in all the ABSs samples involved particle cavitation, crazing and shear yielding. This observation indicates that rubber particle cavitation plays an important role in the toughness enhancement.
Purpose
The purpose of this paper is to provide macromechanical insight into the fatigue behaviour of laser sintered parts and to understand the influence of the laser sintered surface structure on this behaviour.
Design/methodology/approach
A background on the technological maturity of manufacturing processes and the demand for structural and aesthetic properties of laser sintered plastic products is given. As the contribution of surface structure on part quality was the focus, laser sintered specimens with and without surface finishes, as well as injection moulded specimens were used. The latter simply served as a comparison and was not intended to qualify injection moulding. The study comprises the determination of short‐term tensile properties, the load increase method for investigating fracture and deformation behaviours, and fatigue crack propagation analysis.
Findings
According to the test results, the contribution of laser sintered surface structures to relevant mechanical properties can be neglected. Under dynamic loading conditions, laser sintered specimens achieved a longer lifetime but showed less deformation capabilities in contrast to injection moulded specimens. In general, laser sintered specimens presented considerable resistance to crack initiation and propagation.
Research limitations/implications
Because of the long‐term approach of the research, the number of tests conducted per lot was limited. Thus, the effects of different process settings and the reproducibility could not be fully analysed.
Practical implications
The studied fatigue behaviour of laser sintered specimens has implications for the functional testing of parts or components, for the product and process design as well as for the general compatibility of laser sintering as a manufacturing technology of end‐customer products.
Originality/value
The value of this paper lies in the better understanding of deformation and fracture behaviours of laser sintered polymers.
Purpose
The purpose of this paper is to investigate the mechanisms controlling the bond formation among extruded polymer filaments in the fused deposition modeling (FDM) process. The bonding phenomenon is thermally driven and ultimately determines the integrity and mechanical properties of the resultant prototypes.
Design/methodology/approach
The bond quality was assessed through measuring and analyzing changes in the mesostructure and the degree of healing achieved at the interfaces between the adjoining polymer filaments. Experimental measurements of the temperature profiles were carried out for specimens produced under different processing conditions, and the effects on mesostructures and mechanical properties were observed. Parallel to the experimental work, predictions of the degree of bonding achieved during the filament deposition process were made based on the thermal analysis of extruded polymer filaments.
Findings
Experimental results showed that the fabrication strategy, the envelope temperature and variations in the convection coefficient had strong effects on the cooling temperature profile, as well as on the mesostructure and overall quality of the bond strength between filaments. The sintering phenomenon was found to have a significant effect on bond formation, but only for the very short duration when the filament's temperature was above the critical sintering temperature. Otherwise, creep deformation was found to dominate changes in the mesostructure.
Originality/value
This study provides valuable information about the effect of deposition strategies and processing conditions on the mesostructure and local mechanical properties within FDM prototypes. It also brings a better understanding of phenomena controlling the integrity of FDM products. Such knowledge is essential for manufacturing functional parts and diversifying the range of application of this process. The findings are particularly relevant to work conducted on modeling of the process and for the formulation of materials new to the FDM process.
Fused-deposition (FD) is a robotically controlled ``fiber'' extrusion process that produces a new class of materials
with a variety of controllable mesostructural features related to fiber layout and the presence of voids. Mesostructural features of importance to the stiffness and strength of unidirectionally extruded materials were
characterized as a function of the processing variables. Samples were made using the Stratasys FDM1600
Modeler with the P400 acrylonitrile-butadiene-styrene plastic. Results showed that the void geometry/density
and the extent of bonding between contiguous fibers depended strongly on the fiber gap and extrusion flow
rate. Settings for minimum void and maximum fiber-to-fiber bonding were determined. Void and bond length
densities in the plane transverse to the fiber extrusion direction varied from 4 to 16 per cent and 39 to 73 per
cent respectively. The results quantify the important mesostructural features as a function of the FD process
variables and are expected to find use with other FD materials
An experimental study of the mechanical behavior of fused-deposition (FD) ABS plastic materials is described. Elastic moduli and strength values are determined for the ABS monofilament feedstock and various unidirectional FD-ABS materials. The results show a reduction of 11 to 37 per cent in modulus and 22 to 57 per cent in strength for FD-ABS materials relative to the ABS monofilament. These reductions occur due to the presence of voids and a loss of molecular orientation during the FD extrusion process. The results can be used to benchmark computational models for stiffness and strength as a function of the processing parameters for use in computationally optimizing the mechanical performance of FD-ABS materials in functional applications.
Tensile strength, modulus of rupture, and impact resistance were found for different layer orientations of ABS rapid prototype solid models. The samples were fabricated by a Stratasys rapid prototyping machine in five different layer orientations. The 0° orientation where layers were deposited along the length of the samples displayed superior strength and impact resistance over all the other orientations. The anisotropic properties were probably caused by weak interlayer bonding and interlayer porosity.
The objective of this paper is to investigate the applicability of a very simple new method, based on load separation criterion, developed for evaluating J-R curves in steels, when applied to ABS polymers. This technique proposes the testing of a single precracked specimen and a single blunt notched specimen. The latter provides a method to detect the plastic displacement range during crack tip blunting in which the assumption of load separation criterion in the precracked specimen is valid, and also allows determination of JIC independently of J-R curve determination. The deformation material function is assumed to be a Ramberg-Osgood type law deformation function which leads to a very easy procedure to determine J-R curves. The J-R curve resulting from this new method is compared with one resulting from a traditional multiple specimen J-R curve determination method. Both results are in good agreement.
Tensile properties of injection and compression molded ABS, terpolymer of acrylonitrile, butadiene, and styrene, were measured as a function of aging time at 40 to 90°C. Both air and nitrogen atmospheres were employed to separate the oxidative and thermal effects. Results demonstrate that tensile elongation is drastically reduced by oven aging at 50 to 90°C, even when a nitrogen atmosphere is employed. Aging in air causes changes in the infrared spectra of ABS and these changes can he monitored in thick samples using the frustrated multiple internal reflection (FMIR) technique. The FMIR technique also provides information on the changes in polybutadiene distribution near the surface of molded parts. The loss of tensile elongation after oven aging is attributed to annealing of the glassy styrene-acrylonitrile matrix. This is supported by differential scanning calorimetry. The tensile elongation is found to he recoverable by reheating to processing temperatures.
A high speed puncture impact apparatus was used to measure impact loss in thermally aged ABS (acrylonitrilebutadiene-styrene) as a function of time and temperature. Impact energy values decreased to a low level and degraded surface layer thickness increased as a function of aging time at three aging temperatures. Systematic removal of surface layers from thermally aged samples progressively increased impact energy values to control levels. Infrared spectroscopy, differential scanning calorimetry and molecular weight data indicate that degradation occurs in the rubber, graft and rigid phases at different times during the thermal aging period. Microscopy results show a critical degraded layer thickness which causes brittle failure of the entire sample.
The fracture toughness of acrylonitrile-butadiene-styrene (ABS) was determined by three J-integral methods, ASTM E813-81, E813-87, and by hysteresis. The critical J values (J1c) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813-81 and hysteresis methods result in comparable J1c values, whereas the ASTM E813-87 was ∼40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the corresponding J1c represents a physical event of crack initiation. The elastic storage energy. The input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to the J1c obtained from the E813-81 or the hysteresis method.
The toughness and impact resistance of a high thermal resistant poly(acrylonitrile-butadiene-styrene) (ABS), a rubber toughened polymer are investigated. The specimen is characterized by transmission electron microscopy (TEM). The extensive rubber particle cavitation shown on the TEM micrographs represents the genuine deformation behavior of the ABS under tensile testing. Although some artefacts were generated by the microtoming process, Due to improper sectioning of the rubber particles, the artefacts do not affect the overall fracture behavior revealed by the TEM micrograph.
The structural integrity and durability of a construction are highly dependent on the material quality. Poly(Acrylonitrile-Butadiene-Styrene) Copolymer (ABS) is a material which is preferably chosen for high performance products, because of its superior toughness. The toughness of ABS is revealed by its high fracture strain in a tensile test, and high notched Izod impact fracture energy. However, the fatigue resistance of ABS is less favourable. This investigation is mainly devoted to the fatigue behaviour of ABS and to the fracture strain and the notched Izod fracture energy. Various mechanical tests, performed in conjunction with scanning electron microscope investigations of the fracture surfaces, demonstrate that fracture initiates from small defects which are abundantly present in the material. Especially the fatigue fracture surfaces show numerous cracks which had initiated from the defects. The fracture strain in tensile tests is high, but shows a large scatter. It is demonstrated that the fracture strain is also related to the presence of defects. A pre-fatigue load up to 40% of the anticipated fatigue life, followed by a tension test shows a significant reduction of the fracture strain as compared with a tension test on non damaged as-moulded material. Microscopic investigations show that this fracture strain reduction is caused by the presence of small cracks which initiated from the defects, during the preceding fatigue load. A similar but much smaller effect of pre-fatigue was observed for notched Izod tests. Finally it is concluded that the fatigue behaviour of ABS is dominated by the growth live of microscopic small cracks from material defects.
In this study, a transparent acrylonitrile–butadiene–styrene polymer alloy was tested in a range of biaxial stress states and a yield locus was generated. The onset of microscopic damage was detected by in situ light transmission measurements. The macroscopic yield locus followed a linear behavior on an octahedral shear stress vs. mean stress plot and the onset of microscopic damage was dependent on both shear and mean stresses. Our findings indicate that macroscopic ductility arises from damage in the polymer at two distinct length scales. On the scale of the rubber particle (0.1–0.2 um), damage occurs via particle debonding from the matrix. At a length scale intermediate between the particle size and macro scale, damage occurs through the formation of micro crack arrays with a well-defined pattern.
An experimental investigation of mixed mode I/II fracture in Norway spruce (Picea abies) is presented. Mixed mode fracture is studied in two principal crack systems, RL and LR, in which the crack planes extend along and across the wood fibres, respectively.The investigation shows that onset of mixed mode cracking can be predicted with a very simple fracture criterion in both these crack systems. However, the applicability of the fracture criterion to cross-fibre cracks is limited to configurations, in which the crack tip T-stress, i.e. the non-singular stress acting parallel to the crack plane, is low.
The suitability of J–R curve fitting methods proposed by ASTM E 813-81 and E 813-87 metal standards in fitting ABS J–R curves is discussed. Tests were carried out at room temperature on one commercial grade ABS resin in three-point bending.Specimens were precracked with a razor blade and tests were performed over a X20 range of crosshead rate in the quasistatic regime.Specimens of different geometric relationships (B/W, a/W, smooth specimens of different thickness, and side-grooved specimens) were assayed.The two ASTM fitting procedures were also checked against data reported by other authors for other ABS type resins.Model appropriateness was checked by statistical analysis.Results appeared to be geometrically independent for deeply notched specimens. No significant variation in the J–R curve was found for changes in the displacement rate. Both J–R curve fittings appeared to be adequate.The ASTM E 813-87 procedure led to less conservative critical initiation JIC values.
Yielding at the end of a slit in a sheet is investigated, and a relation is obtained between extent of plastic yielding and external load applied. To verify this relation, panels containing internal and edge slits were loaded in tension and lengths of plastic zones were measured.
Fused deposition modelling (FDM) is a fast growing rapid prototyping (RP) technology due to its ability to build functional parts having complex geometrical shape in reasonable time period. The quality of built parts depends on many process variables. in this study, five important process parameters such as layer thickness, orientation, raster angle, raster width and air gap are considered. Their influence on three responses such as tensile, flexural and impact strength of test specimen is studied. Experiments are conducted based on central composite design (CCD) in order to reduce experimental runs. Empirical models relating response and process parameters are developed. The validity of the models is tested using analysis of variance (ANOVA). Response surface plots for each response is analysed and optimal parameter setting for each response is determined. The major reason for weak strength may be attributed to distortion within or between the layers. Finally, concept of desirability function is used for maximizing all responses simultaneously. (C) 2009 Elsevier Ltd. Ail rights reserved.
In recent years, the interest in the problem of brittle fracture and, in particular, in the theory of cracks has grown appreciably in connection with various technical applications. Numerous investigations have been carried out, enlarging in essential points the classical concepts of cracks and methods of analysis. The qualitative features of the problems of cracks, associated with their peculiar nonlinearity as revealed in these investigations, makes the theory of cracks stand out distinctly from the whole range of problems in terms of the theory of elasticity. The chapter presents a unified view of the way basic problems in the theory of equilibrium cracks are formulated and discusses the results obtained thereby. The object of the theory of equilibrium cracks is the study of the equilibrium of solids in the presence of cracks. However, there exists a fundamental distinction between these two problems, The form of a cavity undergoes only slight changes even under a considerable variation in the load acting on a body, while the cracks whose surface also constitutes a part of the body boundary can expand even with small increase of the load to which the body is subjected.
Fracture toughness resistance curves describe a material's resistance against crack propagation. These curves are often used to characterize biomaterials like bone, nacre or dentin as these materials commonly exhibit a pronounced increase in fracture toughness with crack extension due to co-acting mechanisms such as crack bridging, crack deflection and microcracking. The knowledge of appropriate stress intensity factors which depend on the sample and crack geometry is essential for determining these curves. For the dental biomaterials enamel and dentin it was observed that, under bending and tensile loading, crack propagation occurs under certain constant angles to the initial notch direction during testing procedures used for fracture resistance curve determination. For this special crack geometry (a kink crack of finite length in a finite body) appropriate geometric function solutions are missing. Hence, we present in this study new mixed-mode stress intensity factors for kink cracks with finite kink length within samples of finite dimensions for two loading cases (tension and bending) which were derived from a combination of mixed-mode stress intensity factors of kink cracks with infinitely small kinks and of slant cracks. These results were further applied to determine the fracture resistance curves of enamel and dentin by testing single edge notched bending (SENB) specimens. It was found that kink cracks with finite kink length exhibit identical stress fields to slant cracks as soon as the kink length exceeds 0.15 times the initial straight crack or notch length. The use of stress intensity factor solutions for infinitely small kink cracks for the determination of dentin fracture resistance curves (as was done by other researchers) leads to an overestimation of dentin's fracture resistance of up to 30%.
Although the mode I (tensile opening) fracture toughness has been the focus of most fracture mechanics studies of human cortical bone, bones in vivo are invariably loaded multiaxially. Consequently, an understanding of mixed-mode fracture is necessary to determine whether a mode I fracture toughness test provides the appropriate information to accurately quantify fracture risk. In this study, we examine the mixed-mode fracture of human cortical bone by characterizing the crack-initiation fracture toughness in the transverse (breaking) orientation under combined mode I (tensile opening) plus mode II (shear) loading using samples loaded in symmetric and asymmetric four-point bending. Whereas in most structural materials, the fracture toughness is increased with increasing mode-mixity (i.e., where the shear loading component gets larger), in the transverse orientation of bone the situation is quite different. Indeed, the competition between the maximum applied mechanical mixed-mode driving force and the weakest microstructural paths in bone results in a behavior that is distinctly different to most homogeneous brittle materials. Specifically, in this orientation, the fracture toughness of bone is markedly decreased with increasing mode-mixity.
Rubber particle cavitation on toughness enhancement of SMI-modificed poly(ABS)
- Jar
ASTM D6068-10 - Standard Test Method for Determining J-R Curves of Plastic Materials, ed
- Astm
Maximizing the strength of fused-deposition ABS plastic parts, presented at the 10th Solid Free-form Fabrication Symposium Proceedings
- J F Rodriguez
- J P Thomas
- J E Renaud