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Ultrasonic consolidation of thermoplastic composite prepreg for automated fiber placement
Abstract
To address the industrial need for manufacturing advanced thermoplastic composite parts with less energy, waste, and time and at lower cost, the feasibility of automated fiber placement using ultrasonic consolidation (UC) is investigated as an alternative to hot gas torch, laser, and infrared (IR) heating. The flexural stiffness and strength of simple flat parts made using UC and also thermal pressing per manufacturer’s specifications are measured by three-point bending and compared. Whereas UC proved to be more effective in welding polyethylene terephthalate/carbon prepreg tape than thermal pressing for both unidirectional and quasi-isotropic layups, the opposite was true for high-density polyethylene/glass, although optimal welding process parameters may not have been used. Finally, a simple transient conduction model is used to predict temperature rise in the thickening laminate and is compared to experimental measurements.
... Therefore, thermal behaviour plays a vital role here as it provides details on optimizing the temperature distribution during processing. The heating system in the compaction device is among the most challenging elements in literature [67][68][69]. Basically, the melt fusion bonding process comprises two composite parts/plies which are bonded through melting their surfaces while subjected to pressure [41]. There are various heating procedures that enable the attainment of this level of bonding which includes discontinuous and static procedures where the plies are initially stacked and further consolidated through continuous methods (e.g., laser, hot gas, or infrared (IR) heating) whereby consolidation occurs while the tape/prepregs are kept in motion [70,71]. ...
... Hot gas heating is highly effective for attaining high temperatures. However, this system is renowned for wasting a significant amount of energy due to its convective heat transfer medium which is regarded as a lengthy dynamic response time, and this reduces its heating efficiency and reduces the process control performance which indirectly makes attaining the necessary general production become a challenge [67,69]. For the hot gas torch systems, air can be used as the gas [74,75], however, nitrogen is widely employed for setups with a single torch [76][77][78] or two torches [79][80][81][82][83]. ...
... CO 2 lasers can be too big for a focused mounting on the placement head during automated fabrications [96]. Additionally, due to their lengthy wavelength, the suitability for fibre optic delivery is hampered as they have higher adsorption rates of the wavelengths [69,96]. Typically, the CO 2 laser output is a tiny round point while a rectangular or linear distribution is the desired choice because uniform heating across the width of the substrate and incoming tape is produced [96]. ...
Thermoplastic composite pipes (TCP) are a form of fibre reinforced thermoplastic pipes that have proven benefits such as being lightweight and non-corrosive. However, during manufacturing, certain defects are induced because of certain parameters which eventually affect TCP performance in-service. Current manufacturing techniques are challenged with on-the-spot detection as the pipe is regularly monitored. When a defect is noticed, the process stops, and action is taken. However, stopping the process is costly; hence it is vital to decrease downtime during manufacturing. Potential solutions are through process optimisation for defect reduction and an in-depth understanding of the effect of parameters that cause defect formation in the pipe. This article provides an overview of manufacturing influence on the end performance. This is intimately linked to the material features, properties, and performance in-service. The material features are the determinants for the manufacturing technique to be used. For TCP, it is a melt fusion bonding process involving heating and consolidation among other factors such as the consolidation speed and pull force. Thermal behaviour is essential at this phase as it determines the curing rate and this study indicates that laser heating is the better heat source in efficiency terms. Defects such as fibre misalignments, voids, and delamination are induced during manufactuirng are explored. The sources of these defects have been discussed herein as well as the secondary defects caused by them with the consideration of residual stress impact. The presence of manufacturing defects has been identified to influence the strength and stiffness, interlaminar shear strength, toughness, and creep performance. In addition the study shows there is a need to explore the state of the art in defect characterization during manufacturing for TCP. The in-situ characterization aims to derive high-quality TCP with reduced defects and need for repairs, and increased production rate in safe and eco-friendly conditions while maintaining the current manufacturing process.
Graphical abstract
... This results in a significant increase in the operating costs [43,44]. Another drawback of the hot gas torch is its low energy efficiency [43,46]. In order to improve the heating process, hot gas heating can be used together with methods such as preheating of the composite fibers or tapes [36,47] and using a heated mandrel or tool [48]. ...
... Additional rollers can be added to increase the contact time [35]. Researchers have studied the ultrasonic ISC of FRTP composites in the forms of commingled yarns and prepreg tapes, with thermoplastic matrices including poly(ethylene terephthalate) (PET), PP and high density polyethylene (HDPE) [35,46,56,57]. One of the limitations of ultrasonic welding is the dependence of the heat transfer process on the FRTP material properties, including stiffness, hardness and damping response [55]. ...
... One of the limitations of ultrasonic welding is the dependence of the heat transfer process on the FRTP material properties, including stiffness, hardness and damping response [55]. Rizzolo and Walczyk reported that ultrasonic welding is effective for the consolidation of carbon/PET but less so for glass/HDPE [46]. ...
Fiber reinforced thermoplastic composites are gaining popularity in many industries due to their short consolidation cycles, among other advantages over thermoset-based composites. Computer aided manufacturing processes, such as filament winding and automated fiber placement, have been used conventionally for thermoset-based composites. The automated processes can be adapted to include in situ consolidation for the fabrication of thermoplastic-based composites. In this paper, a detailed literature review on the factors affecting the in situ consolidation process is presented. The models used to study the various aspects of the in situ consolidation process are discussed. The processing parameters that gave good consolidation results in past studies are compiled and highlighted. The parameters can be used as reference points for future studies to further improve the automated manufacturing processes.
... Apart from CF/PEEK prepregs, other high-performance thermoplastics such as polyamide (PA-6), polyethersulphone (PES), and polyethylene terephthalate (PET) have also been exploited by many researchers in the recent past for automated manufacturing of composite laminates. In this context, Rizzolo and Walczyk [192] used ultrasonic consolidation (UC) during the fabrication of prepregs made out of carbon fiber reinforced (CF/PET) and high-density polyethylene reinforced with glass fibers (GF/HDPE) using the AFP process. Three-point bending tests revealed that the UC CF/PET laminates showed significantly higher flexural strength and stiffness compared to those exhibited by thermally pressed specimens. ...
... Based on the ongoing research in the field, a highly efficient and fully automated composite manufacturing environment using advanced materials is expected in the near future. Carbon/epoxy prepreg AFP, ATP [178] Carbon/epoxy prepreg AFP [180] Carbon/epoxy prepreg AFP [182] Carbon/epoxy prepreg AFP [183] CF/epoxy prepreg AFP [197] GF/epoxy AFP [198] CF/epoxy AFP, Autoclave [199] CF/epoxy AFP [200] CF/epoxy prepreg AFP [201] Thermoplastic [53] CF/PEEK LATP, Autoclave [186] CF/PEEK LATP, Autoclave [187] CF/PEEK LATP [189] CF/PEEK LATP [190] CF/PET AFP [192] GF/HDPE AFP [192] CF/PES AFP [193] GF/HDPE, GF/Nylon AFP [56,202] ...
... Based on the ongoing research in the field, a highly efficient and fully automated composite manufacturing environment using advanced materials is expected in the near future. Carbon/epoxy prepreg AFP, ATP [178] Carbon/epoxy prepreg AFP [180] Carbon/epoxy prepreg AFP [182] Carbon/epoxy prepreg AFP [183] CF/epoxy prepreg AFP [197] GF/epoxy AFP [198] CF/epoxy AFP, Autoclave [199] CF/epoxy AFP [200] CF/epoxy prepreg AFP [201] Thermoplastic [53] CF/PEEK LATP, Autoclave [186] CF/PEEK LATP, Autoclave [187] CF/PEEK LATP [189] CF/PEEK LATP [190] CF/PET AFP [192] GF/HDPE AFP [192] CF/PES AFP [193] GF/HDPE, GF/Nylon AFP [56,202] ...
In recent years, new revolutionary paradigms generally indicated using the term Industry 4.0, have been conceived and are progressively applied in several manufacturing systems to achieve a smarter, more effective, and sustainable production. This article aims to depict the present and future scenarios related to the application of Industry 4.0 concepts to polymer composites manufacturing. To provide a view on future potential, and open new research frontiers, the article attempts to address through elaborate discussions two major questions:
• What is the future of fiber-reinforced polymer composites manufacturing in the Industry 4.0 context?
• What are the recent and potential developments in robotic and additive manufacturing of advanced fiber-reinforced composites?
The article, in addition, connects new avenues in additive manufacturing, for instance, incorporating topology optimization, design opportunities, recent industrial developments in machines and patent disclosures, and defect detection/mitigation during manufacture. Similarly, recent developments concerning robotic Automated Fiber/Tape Placement have been provided, discussing state-of-the-art research trends and future opportunities.
... Besides, it is emphasized that inclusion of a plasticizer has a strong influence on the processing window and on the weld quality [5]. ...
... The waterproof composites are welded using ultrasonic welding process for the specialized applications in the studies. Various recommendations are made to enhance the ultrasonic welding technique to offer theoretical guidance for further research and usages in different industries [5]. Production of micro devices made from thermoplastic materials using ultrasonic welding method is a optimal technology for the current manufacturing scenario. ...
... For small scale production as in case of micro devices industry, it is less expensive as compared to other methods of plastic joining. Ultrasonic welding process is being deployed for past ten years and adapted in the industry for multiple purposes as shown in figure 1 [2][3][4][5][6]. ...
Ultrasonic welding of polymers is an economically viable joining technique which eludes the addition of solvents or adhesives but causes localized heating at the interface by using relatively short cycle times [1]. Ultrasound welding is a high-frequency continuous joining technique. It is appropriate for joining small and larger regions in a sequential manner [2]. It is the technique that offers a good alternative to automotive, medical, packaging, appliance, textile, electronics, and others. The merits of ultrasonically assembled parts reveal clean and reliable bonds to the components. Ultrasonic welding is a swift process wherein a frequency in the range of 18–70 kHz is being used. Output value differs from hundreds of watts to a few kilowatts. Ultrasonic welding machine comprises a booster, transducer, horn, and electrical power supply (generator). The transducer (process controller) receives the electrical signal supply from the generator. Transducer converts electrical signal into mechanical longitudinal vibrations which are transmitted to horn to bond the interface of the material.
... Although the application of thermoplastic composite materials in civil aircraft has gradually aroused an upsurge in research upsurge abroad and in the future, the largescale application of thermoplastic composite materials in civil aircraft is the inevitable result of the development of advanced materials and the progress of manufacturing technology. Nevertheless, the continuous fiber-reinforced thermoplastic composite in situ consolidation technology has not been applied in the manufacturing of civil aircraft structural components effectively at present [21,22]. The reason is the significant difference between the AFP in situ consolidation process of thermoplastic composite and the AFP of thermosetting composite. ...
... In the process of in situ consolidation, the prepreg and the substrate are melted in the bonding area under the heating of the heat source, and pressure is applied through the Although the application of thermoplastic composite materials in civil aircraft has gradually aroused an upsurge in research upsurge abroad and in the future, the large-scale application of thermoplastic composite materials in civil aircraft is the inevitable result of the development of advanced materials and the progress of manufacturing technology. Nevertheless, the continuous fiber-reinforced thermoplastic composite in situ consolidation technology has not been applied in the manufacturing of civil aircraft structural components effectively at present [21,22]. The reason is the significant difference between the AFP in situ consolidation process of thermoplastic composite and the AFP of thermosetting composite. ...
Automated fiber placement (AFP) in situ consolidation of continuous CF/high-performance thermoplastic composite is the key technology for efficient and low-cost manufacturing of large thermoplastic composites. However, the void in the in situ composite is difficult to eliminate because of the high pressure and the short consolidation time; the void content percentage consequently is the important defect that determines the performance of the thermoplastic composite parts. In this paper, based on the two-dimensional Newtonian fluid extrusion flow model, the void dynamics model and boundary conditions were established. The changes of the void content percentage were predicted by the cyclic iteration method. It was found that the void content percentage increased gradually along the direction of the layers’ thickness. With the increasing of the laying speed, the void content percentage increased gradually. With the increasing of the pressure of the roller, the void content percentage gradually decreased. When the AFP speed was 11 m/min and the pressure of the compaction roller reached 2000 N, the void content percentage of the layers fell below 2%. It was verified by the AFP test that the measured results of the layers’ thickness were in good agreement with the predicted results of the model, and the test results of the void content percentage were basically equivalent to the predicted results at different AFP speeds, which indicates that the kinetic model established in this paper is representative to predict the void content percentage. According to the metallographic observation, it was also found that the repeated pressure of the roller was helpful to reduce the void content percentage.
... IR heaters are one of the most common heat sources seen in AFP manufacturing of thermoset materials. Heat transfer from the IR heater to the substrate is done through radiation [65]. Calawa and Nancarrow [66] developed a quartz lamp IR heater with the advantages of short response time, durability, and longest wavelength with high power output. ...
... For this reason, a reflector is often incorporated to ensure most of the emitted energy is in a useful direction [66]. This heating system has a main disadvantage of inefficient heat transfer and non-uniform heating due to the wide dispersion of the heat [65]. Further, the heat generated by the IR heaters is not high enough for manufacturing with thermoplastic materials. ...
Automated fiber placement (AFP) is a composite manufacturing technique used to fabricate complex advanced air vehicle structures that are lightweight with superior qualities. The AFP process is intricate and complex with various phases of design, process planning, manufacturing, and inspection. An understanding of each of these phases is necessary to achieve the highest possible manufacturing quality. This literature review aims to summarize the entire AFP process from the design of the structure through inspection of the manufactured part to generate an overall understanding of the lifecycle of AFP manufacturing. The review culminates with highlighting the challenges and future directions for AFP with the goal of achieving a closed loop AFP process.
... Although it is an efficient approach to achieve an appropriate temperature, its disadvantages are its complex control and typical excessive waste of much of the available energy. 81,82 IR heating is very similar to open flame heating, with the significant difference being that the IR source is brought close to the two parts being welded, without touching the surface. Heat is transferred to the composite workpiece essentially by radiation. ...
... Although ultrasonic consolidation seems to have received less attention, it is also a rapid heating method and can exert the desired pressure on a composite surface. 81 LED heating technology using a plurality of LEDs for thermoset AFP systems can provide heat with a little reaction time, and the corresponding heat transfer models were established by Orth et al. 88 ...
Automated fibre placement (AFP) systems have successfully intensified the demand for high-quality composite component manufacturing in both the military and civilian fields. One of the main elements of these systems is the AFP mechanism for accomplishing individual fibre delivery, clamp/cut/restart (CCR) and the consolidation process, and it consists of several functional sub-mechanisms presenting strong coupling relationships and motion sequences. This review aims to summarize the development of AFP mechanisms and the associated research achievements and provide insight into the research challenges in promoting innovative design in such mechanisms. The systematic development of AFP systems is reviewed in detail, and subsequently, engineering tendency and the general principle of AFP mechanisms are introduced. Focusing on the mechanism design of AFP sub-mechanisms, including the creel assembly CCR and compaction mechanisms, the mechanical schemes as well as the AFP process parameter control are discussed. To improve system reliability and fully optimise AFP mechanisms, the essential theoretical foundation for AFP mechanisms are provided. It is believed that this attempt will help to change the design and optimisation of similar complete mechanisms. Based on the reviewed research, overall remarks and perspectives are presented to serve as a guide for exploring the possibility of novel easy-to-use and cost-effective integrated AFP applications.
... Then, the substrate layer enters the natural air-cooling zone to undergo cooling and consolidation. In the process of thermoplastic fiber placement, the heat transfer model is the primary model to start with as part of the process modeling with the resulting temperature [21][22][23][24]. At present, hot-air heating is widely used in the field of automatic placement of composite materials due to its low cost and small heating window. ...
... The results showed that it is beneficial to improve the fusion strength when the substrate layer is heated to a temperature above the melting point multiple times, but this also increases the porosity between the layers. Lionetto et al. [27] established a simple two-dimensional model of thermoplastic prepreg tape, studied the In the process of thermoplastic fiber placement, the heat transfer model is the primary model to start with as part of the process modeling with the resulting temperature [21][22][23][24]. At present, hot-air heating is widely used in the field of automatic placement of composite materials due to its low cost and small heating window. ...
Under the effect of different process parameters, the temperature field inside the thermoplastic fiber is very complex and directly affects the fusion quality between the resins. Considering the heat transfer behavior of thermoplastic fiber polyether ether ketone (PEEK) as the research object, a mathematical model of heat transfer in the thermoplastic composite fiber placement with the relevant boundary conditions was established. Ansys Parametric Design Language (APDL) was used to generate the finite element model and simulate the transient process, not only to explore the influence of various process parameters on the temperature field, but also to build an online temperature field measurement system. The influence rules of placement process parameters and mold initial temperature with respect to the temperature field in the first layer were obtained. Combining the relationship between heating temperature and placement speed, when the first layer was laid, the placement process temperature could be quickly reached by low speed and high temperature. The temperature data were collected by the online detection system. Compared with the temperature data from the simulation, the error was below 8%, which verified the correctness of the heat transfer model. The academic research results will lay a theoretical foundation for the thermoplastic fiber placement.
... Continuous GF/polypropylene, GF/high-density polyethylene (HDPE), and CF/polyethylene terephthalate (PET) have been fabricated by auto fiber placement (AFP) using ultrasonic consolidation. 31,32 Chu et al reported the interlaminar shear strength (ILSS) of ultrasonic-assisted AFP parts could as good as those done with hot-press process. 31 Hence, ultrasonic vibration can be an alternate heating source to bond the thermoplastic prepregs at a high speed and efficiency in the AM process. ...
... As a reference, flexural properties of unidirectional fiber-reinforced composites fabricated by the proposed method were compared with additively manufactured fiber-reinforced composites by other methods, including short carbon-fiber (SCF) composites printed by SLS, 35 FDM, 36 and continuous carbon-fiber (CCF) composites fabricated by FDM, 12,[14][15][16]19,20,[37][38][39][40] ultrasonic-assisted auto-fiber placement (UAFP), 32 and laser-assisted laminated object manufacturing (LA-LOM). 21 As shown in Figure 3B, the proposed method exhibits the highest flexural modulus and strength for all reported AM methods. ...
Additive manufacturing (AM) of continuous fiber‐reinforced thermoplastic composites (CFRTPCs) has drawn increasing interest and great attention in academic and industrial communities due to its capability of manufacturing complex lightweight structures with high strength at a low cost. In this study, we proposed a novel AM technique to fabricate CFRTPCs using carbon fiber prepreg sheets based on a novel method: ultrasonic‐assisted laminated object manufacturing (UA‐LOM). The prepreg sheets were first cut into 2D shapes, then every eight layers of the sheets were successively consolidated by an ultrasonic‐vibration roller to fabricate one 3D composite part at a faster speed than conventional AM processes where materials are deposited layer by layer. Samples with controlled fiber alignments were prepared for mechanical tests. The post‐processing hot press was carried out to further improve mechanical properties of the additively manufactured components. Results showed that the unidirectional composite samples displayed an ultra‐high tensile strength of 1760.2 (±71.7) MPa and a tensile modulus of 105.7 (±7.2) GPa. The proposed method exhibited superior mechanical performance compared to state‐of‐the‐art AM techniques. The hot‐press‐treated AM composite parts in this work approached the benchmark mechanical properties provided by the prepreg manufacturing company using traditional fabrication methods. Overall, the proposed AM methods of CFRTPCs show great potential applications in aerospace and transportation industries. Schematic illustration of the ultrasonic vibration‐assisted laminated object manufacturing method and the properties of printed continuous fiber reinforced thermoplastic composites.
... Nowadays, construction and civil sector has become one of the world's largest consumers of polymer composites and recently fiber reinforced polymer (FRP) composites especially glass fiber reinforced polymer (GFRP) have gained a great worldwide interest in civil, construction and other applications due to their advantages including lightness, high mechanical performance, possibility of fabrication in any shape, ease of installation. The mechanical properties of polymer composites such as glass fiber reinforced polymer composites make fiber matrix attractive for structural and energy absorption applications due to low cost, low density, high stiffness and strength-to-weight ratio [1][2][3][4][5][6][7][8][9]. ...
... This mode of failure distinguishes brittle failure which validates the results obtained from Whitney-Nuismer mathematical model. 7. SEM micrographs revealed the presence of 'hackles' at whole the fiber surfaces in the virgin specimen which are the matrix bonded to the fibers even after the fracture which confirms the presence of a strong bond at the interface between the fiber and the matrix. ...
... This technique, called ultrasonic consolidation (UC), takes advantage of vibrations generated by the waves in to the material in order to facilitate the removal of the air trapped between layers. The benefits in the use of UC are well known for automated lay-up of both thermosetting and thermoplastic composites [15][16][17][18], where ultrasound waves are used for both matrix debulking and curing (heat generation), with a frequency generally in the range of 20-120 kHz [15]. Lionetto et al. [16] presented both experimental and numerical analyses of an automated lay-up process that uses ultrasonic propagation in order to provide pressure and heat during filament winding of thermoplastic matrix composite, reporting a void content within the typical range for composites processed by filament winding and other traditional methods. ...
... Lionetto et al. [16] presented both experimental and numerical analyses of an automated lay-up process that uses ultrasonic propagation in order to provide pressure and heat during filament winding of thermoplastic matrix composite, reporting a void content within the typical range for composites processed by filament winding and other traditional methods. Rizzolo et al. [17] experimentally studied the UC process during AFP of PET/carbon composite samples resulting in significantly higher mechanical properties in comparison with those obtained by hot-press manufacturing process. In their work, Chu et al. [18] analysed the influence of ultrasonic AFP (UAFP) on the mechanical properties and microstructure crystallization of thermoplastic composites showing a good match with properties of the same specimens produced by hot-press. ...
Debulking of prepreg (pre-impregnated resin system) layers during hand lay-up manufacturing of carbon fibre reinforced polymers (CFRP) is a key-step to reduce air content and maximise the mechanical properties of the final product. Debulking is usually performed using vacuum-bag cycles of 10–15 min applied after the lay-up of every three or five prepreg layers, leading to a considerable time-consuming process. In this work, the use of ultrasonic stimulation during vacuum is studied to improve the efficiency of the debulking process and reduce the number of operations in order to decrease the overall manufacturing time. Three CFRP laminates were laid-up using the proposed ultrasonic consolidation (UC) with three different exposition times (5, 10 and 15 min) and cured in autoclave. The UC debulking process consists in a vacuum cycle with ultrasonic waves sent to the uncured material through an ultrasonic transducer. In order to evaluate the efficiency of this process interlaminar shear strength (ILSS) and in-plane compressive properties were tested. Experimental results show for 15 min compressive properties comparable with the ones obtained from reference samples manufactured using the traditional debulking technique, and high improvements in terms of ILSS (>20%). Therefore, UC debulking process can be used during hand lay-up of prepreg in order to improve the interlaminar properties of the final part and reduce the debulking time by over 85%.
... 8 Moving away from rigid panels or coupons, ultrasonic (US)assisted consolidation of thermoplastic composites has been demonstrated through continuous setups for commingled and prepreg materials. 9,10 Literature related to US-based applications for thermoset composite processing is scarce. US tape lamination was originally developed for cryo-tank manufacturing based on automated fiber placement or filament winding. ...
... [20][21][22] However, it is expected that the vibrations may generate local heating of the TCs, acting as energy directors themselves, which should be taken into account when analyzing data. 10,23 In this study, measurements were carried out on UD (4 and 12 plies) samples. This was done to obtain a general temperature range below and above the laminate, during and after the US process. ...
Ultrasonic welding is a common fusion bonding technique to join unreinforced and reinforced thermoplastics. It is expected that applying ultrasonic vibrations to thermoset prepregs can produce heat generation to promote resin flow and consolidation. This paper discusses the feasibility of using ultrasonic vibrations as a high-speed repair technique for carbon fiber/epoxy prepregs to replace the traditional vacuum-bagging scarf setup. Three material types were investigated: out-of-autoclave unidirectional and plain weave prepregs (Cycom® 5320) and a general purpose twill weave prepreg (AS4/Newport 301). Two welding modes were considered: time and travel (vibrations stop once the desired vertical displacement is reached). For each mode, vibration time, travel, force, and amplitude were investigated. Cross-sectional analysis showed that void content equal to or below the vacuum-bagged samples could be achieved with ultrasonic consolidation to meet aerospace standards (≤2%). The following ultrasonic parameters were recommended to preserve prepreg tows integrity and minimize void content: vibration time below 1.0 s, travel between 12.5% and 50% of sample's initial thickness, force equal to or below 100 N, and amplitude below 41.3 μm. Temperature values recorded during the ultrasonic process reached the manufacturer's cure temperature range (120℃ to 180℃), with a predicted maximum degree of cure of 0.24. Interlaminar shear strength values were comparable for ultrasonically consolidated and vacuum-bagged samples. Soft and hard repair patches were applied to open-hole tensile coupons, with up to 50% strength recovery for both repair methods. Overall, ultrasonic consolidation has potential as a time- and cost-efficient repair method for thermoset prepregs.
... Besides the joining of already fabricated CFRP, it was demonstrated that the ultrasonic welding process can also be used for the initial fabrication of CFRP itself made from prepregs, tapes or preforms [13][14][15][16][17][18]. Furthermore, it is possible to use ultrasonic welding to process the so-called In an initial experiment, the prior described ultrasonic fabrication process was used to fabricate CFRP samples, which consisted of one layer of carbon fibers embedded into a PP matrix. ...
... Besides the joining of already fabricated CFRP, it was demonstrated that the ultrasonic welding process can also be used for the initial fabrication of CFRP itself made from prepregs, tapes or preforms [13][14][15][16][17][18]. Furthermore, it is possible to use ultrasonic welding to process the so-called pseudo-prepregs made of continuously commingled glass fibers and PP filaments, which allows to fabricate GFRP within a roll-to-roll process [19,20]. ...
Ultrasonic fabrication of fiber reinforced plastics made from thermoplastic polymer films and carbon or glass fibers enables cycle times of a few seconds and requires investment costs of only some 10,000 €. Besides this, the raw materials can be stored at room temperature. A fiber content of 33 vol % and a tensile strength of approximately 1.2 GPa have been achieved by ultrasonic welding of nine layers of foils from polyamide, each 100 µm in thickness, and eight layers of carbon fibers, each 100 µm in thickness, in between. Besides unidirectional carbon fiber reinforced polymer composite (CFRP) samples, multi-directional CFRP plates, 116 mm, 64 mm and 1.2 mm in length, width and thickness respectively, were fabricated by processing three layers of carbon fiber canvas, each 300 µm in thickness, and eight layers of polyamide foils, each 100 µm in thickness. Furthermore, both the discontinuous and the continuous ultrasonic fabrication processes are described and the results are presented in this paper. Large-scale production still needs to be demonstrated.
... Engineering or commodity thermoplastics have received far less attention within the recent years. Some studies exist investigating PA6 [16,[28][29][30], PA66 [31], PA12 [32,33], or PP [34][35][36][37]. Low-cost thermoplastic matrix systems are particularly of interest for cost-sensitive and high-volume industries such as the automotive sector [38], as they offer easy processability, high toughness, damage tolerance, and better recyclability compared to thermoset structures [39]. ...
Laser-assisted automated tape placement systems are currently the state of the art regarding thermoplastic tape placement. Flashlamp heating systems are rather new in this field of application and offer high energy density with low safety requirements and moderate costs compared to laser-assisted automated tape placement systems. In this study, the effect of processing parameters on interlaminar bonding of carbon fiber-reinforced polyamide 6 tapes is investigated using a flashlamp heating system. The temperature during placement is monitored using an infrared camera, and the bonding strength is characterized by a wedge peel test. The bonding quality of the tapes placed between 210 °C and 330 °C at a lay-up speed of 50 mm/s is investigated. Thermogravimetric analysis, differential scanning calorimetry, and micrographs are used to investigate the material properties and effects of the processing conditions on the thermophysical properties and geometric properties of the tape. No significant changes in the thermophysical or geometric properties were found. Moisture within the tapes and staining of the quartz guides of the flashlamp system have significant influence on the bonding strength. The highest wedge peel strength of dried tapes was found at around 330 °C.
... It should be noted that USW can be used not only for joining laminates for structural components, but for the fabrication of laminates as well [21][22][23][24][25][26][27]. In such cases, their structure is formed due to processes developing at several interfaces, with the unilateral input of mechanical energy converted into frictional heating [28]. ...
The aim of this study was to optimize the ultrasonic consolidation (USC) parameters for ‘PEI adherend/Prepreg (CF-PEI fabric)/PEI adherend’ lap joints. For this purpose, artificial neural network (ANN) simulation was carried out. Two ANNs were trained using an ultra-small data sample, which did not provide acceptable predictive accuracy for the applied simulation methods. To solve this issue, it was proposed to artificially increase the learning sample by including additional data synthesized according to the knowledge and experience of experts. As a result, a relationship between the USC parameters and the functional characteristics of the lap joints was determined. The results of ANN simulation were successfully verified; the developed USC procedures were able to form a laminate with an even regular structure characterized by a minimum number of discontinuities and minimal damage to the consolidated components.
... This is the major distinction between ATL and AFP. Hence, ATL is more suitable for manufacturing large-scale components with a simple structure and low curvature, while AFP can fabricate complex composite structures with high curvature [124]. At present, ALT has been adopted in the aerospace industry to manufacture large-scale composite wall structures of aircraft, such as the wing of the F-22, the tail, horizontal and vertical stabilizing panels of the Boeing 777 and so on. ...
Lightweight fiber-reinforced composite structures have been applied in aerospace for decades. Their mechanical properties are crucial for the safety of aircraft and mainly depend on manufacturing technologies such as autoclave, resin transfer molding and automated layup technology. In recent years, the rapid development of intelligent technology such as big data, deep learning, and machine learning has encouraged the development of manufacturing technologies to become low-cost, automatic, and intelligent. However, the current situation and intellectualization of manufacturing technologies is not well summarized. This paper reviews the advances in manufacturing technologies for fiber-reinforced composite structures, including autoclave, out of autoclave, resin transfer molding technologies, automated layup technology and additive manufacturing technology. Then, these technologies are compared in advantages and disadvantages, and their intellectualization development and challenges are also discussed. Finally, the development trend of intelligent manufacturing technologies and intelligent composite structures are discussed. This work can provide a reference for researchers in the related filed.
... The heating system melts the thermoplastic matrix, and the compaction roller pressure combines the layers. The major heating systems used in AFP include laser beams, hot-gas torches, ultrasonic welding, and infrared (IR) lamps [7,8,9,4]. A comprehensive review of the early developments of the AFP with CFRTP has been performed by Lukaszewicz et al., who demonstrated three advantages of using CFRTP over CFRP: a) they melt upon heating and harden with cooling, which increases their moldability compared to thermosets, b) fast manufacturing cycle, and c) recyclability. ...
... The processes also include heating systems such as hot rollers, gas torches, and laser and infrared irradiation techniques are available [51,55,56]. Other heating methodologies were recently developed: ultrasonic consolidation [57] ...
... in width) but enables the stacking of flat laminates only. ATL is therefore faster but the control of the heat is better for AFP because of smaller samples [13,16,42,44]. ...
Continuous Carbon Fiber (CF)/polyaryletherketone (PAEK) composites have recently attracted interest especially in the aerospace industry due to short-time processes and possible weldability and recyclability. However, their manufacturing remains challenging as it involves several steps such as tape fabrication, tape lay-up and consolidation. This last step mainly aims at achieving a sufficiently low void content composite to obtain the desired mechanical properties. To become an economically viable alternative over classical thermoset-based composites, “in-situ” consolidation or out-of-autoclave (OOA) consolidation processes have to be part of the manufacturing process of CF/PAEK. These techniques have, for now, some limitations which lead to difficulties in producing parts of the same quality as autoclave consolidated ones. Understanding the multi-scale rheological phenomena involved during consolidation is therefore critical, which constitutes the main goal of this review. Reflecting on the literature, guides for improving the OOA and “in-situ” consolidation, both in terms of process and materials, are finally suggested.
... During the on-line consolidation in ATP, the tape is heated above the thermoplastic melting point before laying and is consolidated by a roller applying pressure. The heating of the tape is made possible by a laser or hot air gun/blow torch, or ultrasound is used (Rizzolo and Walczyk 2016;Yassin and Hojjati 2018;Rodriguez-Lence, Martin, and Fernandez Horcajo 2019). Predominantly, the laser heating or blow torch is used since it offers effective localized heating of the tape (Yassin and Hojjati 2018). ...
... The ILSS benefits from higher values of crystallinity, whilst mode I fracture toughness from lower levels; therefore, a trade-off exists that needs to be considered at the design stage. The use of ultrasonic vibration as fast heat source has been proposed [39] with ultrasonic assisted AFP producing materials with a 4.6% void content [40], which is higher than the void content obtained by autoclave processing (<1%) and AFP using either laser or hot gas torch (about 3%). Ultrasonic assisted AFP produces materials with comparable ILSS and higher mode I fracture toughness in comparison to hot pressing manufactured parts. ...
Additive manufacturing of continuous reinforced polymer is currently a focus topic in the composite manufacturing industry as it represents a viable solution to satisfy the requirements of high volume production and automation that could facilitate expanding the use of composite materials and meet sustainability goals. Nevertheless, several challenges need to be addressed to increase the quality standards to match those of parts manufactured by standard composite processing routes. Specifically, consolidation issues appear to be the determining factor which hold the technology back. The present review paper analyses current consolidation techniques utilised in additive processing of composites and identifies the most promising current and future manufacturing technologies capable of complying with stringent sustainability, quality and cost standards.
... More recently, the application of ultrasonic vibrations for melting polymers is gaining importance because of its quicker heat generation than infrared, induction, laser, or any other heating methods. [15][16][17] The mechanism of heating by ultrasonic vibrations involves the generation of frictional heat in polymer molecules that instigate melting. These vibrations are widely utilized for joining thermoplastics by promoting intermolecular diffusion at the substrates interface using the ultrasonic plastic welding process. ...
The ultrasonic energy-assisted manufacturing of fiber-reinforced thermoplastics is gaining importance in recent years because of its quicker heat generation with less energy requirement than other heating methods. However, a semi-finished raw material such as prepreg or preform with prior processing method is predominantly used. This study investigates the manufacturing of fiber-reinforced thermoplastics from dry and solid raw materials using the ultrasonic plastic welding process. Layers of dry thermoplastics and woven roving synthetic fibers are stacked successively and consolidated with high-frequency ultrasonic vibrations. Influential process settings were experimentally realized for different material stacking sequences to obtain a uniform fusion bonding in thermoplastics. The cross-sectional morphology reveals a strong interfacial attraction between fibers and matrix for the higher contact pressure of the ultrasonic horn along with a longer hold duration that promoted an effective resin impregnation through wetting and intermolecular diffusion in thermoplastics, thereby reducing the void contents and increasing the fiber volume in composites. Furthermore, the tensile, flexural, and interlaminar strength of composites are determined and compared with those obtained using the compression molding process. The thermogravimetric and differential scanning calorimetry data provided thermally stable composites. An efficacious composite with substantial properties was manufactured in a cycle time of 10 s.
... However, an effective choice of process that consumes lesser energy, quicker processing, simpler experimental set-up, cost-effective and possibility of automation is needed to meet the future Industry 4.0 requirements. The method of utilizing ultrasonic energy for the manufacturing of thermoplastic composites are gaining importance in recent days due to its quicker heat generation in melting polymers than other methods of heating such as infrared or laser heating [2,3]. Ultrasonic plastic welding (UPW) is a quick process of joining thermoplastics with lesser energy requirement. ...
This research study investigates the development of multi-directional fiber-reinforced
polyamide composite laminates by ultrasonic plastic welding (UPW) process. Layers of woven roved E-glass/ 3K twill carbon fiber mats and thermoplastic sheets are stacked within a metal mould and consolidated under the application of ultrasonic energy to develop polyamide composite laminates. Critical welding parameters were experimentally realized for different sample nomenclatures to obtain a quality laminate. The tensile strength, density, volume and weight fraction of developed laminates were evaluated. A maximum tensile strength of 260 MPa was achieved in a multi-directional glass fiber reinforced polyamide laminate that had a fiber to resin weight fraction of around 45%. The cross-section morphology were analyzed using scanning electron microscope to understand the impregnation of fibers onto polyamide resins. The thermal characterization of laminates using DSC and TG/DTG techniques does not reveal any significant effect on compositional change of the base polymer material upon processing with high-frequency ultrasonic vibrations. This approach provides a new thinking for
manufacturers in developing polymer composite laminates within a shorter cycle time and the possibility of process automation that meets the requirement of Industry 4.0 standards.
... The approach proposes the excitation of the consolidation roller with sub-ultrasonic vibrations in addition to the laser heating in TAFP. Through this, the frequency-dependent shear-thinning effect of the viscoelastic matrix material will be used to decrease the viscosity within the consolidation as well as dissipative heat generation which is known from tape winding [30][31][32] and ultrasonic welding [33][34][35] of the thermoplastic material will be used to compensate the temperature loss and avoid overheating. Both the shear-thinning effect and dissipative heat effect shall have a positive effect on the development of intimate contact and thus on the resulting consolidation quality. ...
For achieving high quality of in situ consolidation in thermoplastic Automated Fiber Placement, an approach is presented in this research work. The approach deals with the combination of material pre-heating and sub-ultrasonic vibration treatment. Therefore, this research work investigates the influence of frequency dependent consolidation pressure on the consolidation quality. A simplified experimental setup was developed that uses resistance electrical heating instead of the laser to establish the thermal consolidation condition in a universal testing machine. Consolidation experiments with frequencies up to 1 kHz were conducted. The manufactured specimens are examined using laser scanning microscopy to evaluate the bonding interface and differential scanning calorimetry to evaluate the degree of crystallinity. Additionally, the vibration-assisted specimens were compared to specimens manufactured with static consolidation pressure only. As a result of the experimental study, the interlaminar pore fraction and degree of compaction show a positive dependency to higher frequencies. The porosity decreases from 0.60% to 0.13% while the degree of compaction increases from 8.64% to 12.49% when increasing the vibration frequency up to 1 kHz. The differential scanning calorimetry experiments show that the crystallinity of the matrix is not affected by vibration-assisted consolidation.
... Ideally, the matrix material has low shrinkage, low coefficient of thermal expansion, viscosity that allows its penetration through the fibre tow, dimensional stability, and it is easily processable into the desired final shape [65]. Continuous fibre-reinforced specimens have been successfully fabricated in the past through hot pressing of preimpregnated sheets [66,67], filament winding [68], compression moulding [69], automated fibre placement [70], and even laminated object manufacturing inspired AM technologies [52,71]. This review focuses on the different fabrication methods and reinforcement technologies of continuous fibrereinforced thermoplastic polymers through FFF. ...
Additive manufacturing technologies have transitioned from the fabrication of prototypes to final product manufacturing with competitive mechanical performance. The use of materials with high strength to weight ratio, and more specifically continuous fibre-reinforced composites, has demonstrated potential when fabricated through fused filament fabrication (FFF). The development and evaluation of such technologies has attracted a lot of attention in recent years, from both academic researchers and from industry, and a plethora of different techniques for its achievement has been proposed. This review presents different methods of FFF for the fabrication of continuous fibre-reinforced composite components as described in both patent and scholarly research literature. Different print head designs and techniques for combining and depositing polymers reinforced with continuous fibre have been developed including pre-impregnation, the use of multiple nozzles for the separate deposition of the fibre and the matrix material, and in situ impregnation of the reinforcing fibre with the matrix material. This review identifies the challenges associated with each of these approaches such as achieving a successful fibre/matrix impregnation, cutting of the continuous fibres during processing, and the introduction of high-performance thermoplastic polymers as the matrix material.
... Its main disadvantages are its reaction time, its low energy efficiency and the heating of surrounding tools. Furthermore, the hot air facilitates the oxidation reactions of the thermoplastic and then requires the use of an inert gas (Rizzolo and Walczyk, 2016). Later on, Beyeler and Guceri (1988) employed a 80 W CO 2 laser beam with a wavelength of 10.6 lm and a circular spot. ...
A comprehensive numerical model is developed for the simulation of the laser-assisted automated tape placement process of carbon fiber/thermoplastic composites. After being heated with a laser, the thermoplastic is welded with the help of a consolidation roller onto a substrate made up of layers of tapes bonded onto one another. Under the pressure applied by the roller, the thermoplastic flows and the tape reaches its final thickness. The numerical model is developed in three sequential steps that can be used to identify the required pressure and temperature distribution to achieve a good bond. Firstly, a heat transfer simulation is performed to determine the temperature distribution into the incoming tape under the consolidation roller. Secondly, a rheological model is developed to examine the polymer flow under the roller and to obtain the pressure field. Finally, the consolidation level between the substrate and the tape is investigated through the degree of intimate contact, which is related to the processing parameters such as the roller velocity, the laser power density and the compaction force.
... Currently, there are also machines where alternative heating systems are being tested, such as an ultrasonic heating source [56,57]. Ultrasonic heating consists of excitation and friction of the polymer molecules due to the low amplitude and high frequency of vibration of the ultrasonic waves. ...
This article provides an overview of the evolution of the in-situ consolidation (ISC) process over time. This evolution is intimately linked with the advancements in each of the steps of the ISC manufacturing process, is additive in nature, and is limited by the orthotropic nature of composite materials and the physicochemical behavior of the thermoplastic matrix. This review covers four key topics: (a) Thermal models—simulation tools are critical to understand a process with such large spatial gradients and fast changes. Heating systems once marked a turning point in the development of industrial ISC systems. Today, lasers are the most recent trend, and there are three key issues being studied: The absorption of energy of light by the material, the laser profile, and the laser focusing. Several approaches have been proposed for the distributed temperature measurements, given the strong temperature gradients. (b) Adhesion—this refers to two subsequent mechanisms. In the first place, the process of intimate contact is one by which two surfaces of thermoplastic pre-impregnated composite materials are brought into contact under pressure and temperature. This enables closure of the existing gaps between the two microscopic irregular surfaces. This process is then followed by the healing or diffusion of polymer molecules across the interface. (c) Crystallinity—mostly influenced by the cooling rate, and strongly affects the mechanical properties. (d) Degradation—this refers to the potential irreversible changes in the polymer structure caused by the high temperatures required for the process. Degradation can be avoided through adequate control of the process parameters. The end goal of the ISC manufacturing process is to achieve a high product quality with a high deposition rate through an industrial process competitive with the current manufacturing process for thermoset composites.
... Its main disadvantages are its reaction time, its low energy efficiency and the heating of surrounding tools. Furthermore, the hot air facilitates the oxidation reactions of the thermoplastic and then requires the use of an inert gas (Rizzolo and Walczyk, 2016). Later on, Beyeler and Guceri (1988) employed a 80 W CO 2 laser beam with a wavelength of 10.6 lm and a circular spot. ...
... As a step forward, we continued to use the same composite material and experimental set-up and showed that the weld uniformity and quality could be improved by using a woven polymer mesh as energy director [17]. Additionally, continuous ultrasonic welding has been demonstrated as an efficient technique for tacking and, potentially, consolidating thermoplastic composite tapes during automated fibre placement (AFP) [18,19] and filament winding (FW) [20,21] processes. Such processes are however relatively different to the welding process subject of the present paper, since they deal with flexible pre-impregnated or semi-impregnated tapes instead of stiff composite adherends or parts. ...
Continuous ultrasonic welding is a promising high-speed and energy-efficient joining method for thermoplastic composite structures. Our aim was to identify and understand differences between the static and continuous ultrasonic welding process for thermoplastic composites. In particular, melting of the interface, consumed power and energy density, temperature evolution at the weld interface, and optimum welding conditions for both types of processes were investigated. This was done for three combinations of welding force and vibrational amplitude, parameters which are known to have a significant effect in both welding processes. Our results showed that for the continuous process the amount of non-welded area under the sonotrode remains constant, while for the static process the amount of non-welded area gradually decreases to zero. Additionally, the optimum vibration times and welding speeds in both processes are similar.
... The ultrasonic frequency was 15-120 kHz in actual use. The mechanical vibration preferentially generated heat at the interface through the friction effect, and therefore the interface bonding strength can reach 100% of the matrix [21]. Fernandez Villegas et al. [22] proved that the high-frequency vibration of the ultrasound can generate ultra-short heating at the interface, causing the thermoplastics to melt, and thus two pieces can be joined together under pressure. ...
All solid-state lithium-ion batteries based on polymer electrolytes have higher safety and energy density, but the low conductivity of lithium ion restricts its application. This study proposes a new method to promote the ionic conductivity of polyethylene oxide (PEO)-based solid electrolytes. In this method, the PEO-based solid electrolyte was first prepared by casting, and then power ultrasound was exerted on the electrolyte by a sandwich structure to modify the electrolyte structure. Through analysis of the performance and microstructure of the electrolyte, it was found that the ultrasonic treatment increased the ionic conductivity by 78%, improved tensile strength and plastic deformation ability, but did not affect the thermal stability and the chemical composition. The ultrasonic vibration, exerting high energy to the solid electrolyte through high-frequency vibration, broke PEO grains and melted them with the frictional heat at boundary. Due to the slight melting and fast solidifying produced by the pulsed ultrasonic treatment, the crystallization was suppressed. The crystallinity was thus reduced by 6.2%, which increased the migration channels of lithium ions and reduced the tortuosity effect. Furthermore, the ultrasonic vibration compressed the electrolyte to produce plastic flow of the material, which made the electrolyte structure more compact. The density of ethylene oxide (EO) units thus increased in the amorphous phase, providing multiple electron-donor coordination sites for the Li+. The hopping distance of the ion between donors decreased, which also facilitated the migration. In addition, the mechanical performance of the electrolyte membrane improved. This study provides a reference for the improvement of polymer based all-solid-state batteries.
... Infrared heaters are more economical, with ease of control, and can be used as preheaters [8]. Heating by ultrasonic waves may also be used, but this method requires secondary processing [9,10]. ...
Automated fibre placement (AFP) is an advanced manufacturing process with a built-in heat and pressure system, an effective method for in situ consolidation of composite parts. In the present study, carbon fibre PA-6 prepregs were laminated by an IR-assisted AFP system, and the effect of process parameters on the resulting part quality was studied. Of the six fundamental process parameters, two parameters, i.e., laying speed and IR power were identified to be critical. Hence, the current study is focussed on the optimization of these two parameters while keeping the others constant. Three different combinations of IR power and laying speed were deduced to be optimised parameters for the material system used. In general, the laying speed should be increased along with the appropriate increase in IR power. Through visual and microstructural inspection, the laminate manufactured with these optimised parameters were found to have fewer defects and better consolidation when compared with samples manufactured with unoptimised combinations.
... The mechanical properties of polymer composites such as glass fiber reinforced polymer composites make fiber matrix attractive for structural applications due to low cost, low density, high stiffness and strength-to-weight [1][2][3][4][5][6][7]. The mechanical properties of the composites depend upon the properties of fibers, the matrix, types of fibers and matrix and stacking sequence of the fibers. ...
... At present, the traditional preparation methods of CFRP mainly include resin transfer molding (RTM), winding molding (WM), autoclave molding (AM), and compression molding (CM). In recent years, there were some new process preparation methods produced by improving the traditional ones, such as lasercured automatic fiber placement molding, ultrasonic rapid curing molding, and electron beam curing molding [4][5][6]. ...
In order to prepare a carbon-fiber-reinforced polymer composite (CFRP) with ideal microstructure and properties, a new vacuum pressure infiltration CFRP method is proposed based on an analysis of existing CFRP preparation process methods. Research on composite material preparation systems was carried out by using this new method principle. The system mainly includes a fiber pre-forming module, a vacuum heating infiltration module, a hot-press curing molding module, and a data acquisition control module. Under the conditions of natural curing at 0 MPa + 6 h + 25 ℃, vacuum heating curing at –0.05 MPa + 30 min + 80 ℃, and hot-press curing at 0.7 MPa + 5 min + 50 ℃, a two-dimensional (2D) CFRP with excellent microstructure and properties was successfully prepared. Observing the microstructure of the prepared composite material, it can be found that the inside of the composite material was sufficiently and uniformly infiltrated, and common preparation defects such as holes and delamination were effectively controlled. Through the performance test, the bending strength of the material reached 790 MPa.
... At present, the traditional preparation methods of CFRP mainly include resin transfer molding (RTM), winding molding (WM), autoclave molding (AM), and compression molding (CM). In recent years, there were some new process preparation methods produced by improving the traditional ones, such as laser-cured automatic fiber placement molding, ultrasonic rapid curing molding, and electron beam curing molding [4][5][6]. ...
2D-T700/E44 composites are prepared by natural curing process, heating curing process and improved compression moulding process (ICM) severally. Test shows the bending strengths of the composites prepared by three processes are 260, 390 and 605 MPa respectively. By observing the microstructure, the composite prepared by the natural curing process has many infiltration voids and cracks in the bending fracture, so the bending strength is low. The composite prepared by the heating curing process also has a small number of voids and cracks in the bending fracture. However, the defects are less than the former. This is due to the high-temperature environment enhances the fluidity of the resin during the period of heating curing. When the ICM is used, the composite is infiltrated in high temperature and high pressure. The voids and cracks are well controlled, so the bending strength reaches 605 MPa. The ICM is beneficial to prepare high-performance materials.
... The heat is produced at the joint interface through a combination of surface and intermolecular friction which leads to matrix melting. The use of ultrasound for automated fiber placement has been recently proposed as an alternative to hot gas torch, laser, and infrared heating [23]. Moreover, ultrasonic wave propagation has the potential for online process monitoring [24,25]. ...
In this work, the potential of preformed thermoplastic matrix composite tapes for the manufacturing of composite pipes by filament winding assisted by in situ ultrasonic welding was evaluated. Unidirectional tapes of E-glass-reinforcedamorphous poly (ethylene terephthalate) were laid up and consolidated in a filament winding machine that was modified with a set-up enabling ultrasonic welding. The obtained composite specimens were characterized by means of morphological and dynamic mechanical analysis as well as void content evaluation, in order to correlate welding parameters to composite properties.
Although conventional methods such as mechanical fastening, adhesive bonding and hot air welding have proven effective in dry conditions, they exhibit diminished efficacy in submerged environments. Hence, a thermoplastic welding technique with minimal dependence on surrounding media is essential. Ultrasonic spot welding (USW) represents a promising approach to thermoplastic joining, offering high efficiency and low operating costs. In this study, we investigate the efficacy of water-submerged ultrasonic spot welding (S-USW) for joining amorphous polyvinyl chloride (PVC) to PVC and semi-crystalline polypropylene (PP) to PP under submerged conditions. Our experimental results show that S-USW leads to a remarkable 39% and 21% increase in lap-shear strength for PVC/PVC and PP/PP welds, respectively, as compared to traditional USW techniques. We corroborate these findings with additional metrics such as Shore-D hardness tests, optical microscopy and scanning electron microscopy imagery, which collectively confirm the improved efficacy of S-USW over USW for joining PVC and PP.
Ultrasonic welding (USW) is an extensively used joining technique employed in various industries such as automotive, aeronautics, packaging, and others, for joining thermoplastic and thermoplastic composites. The strength of USW can be further enhanced through preferential heating with the induction of energy directors (EDs). The present study investigates water-submerged ultrasonic welding (S-USW) using three different ED designs to join 20% short carbon fibre-reinforced polyamide, commonly referred to as CF/PA. This approach improves weld strength and mitigates material degradation caused by rapid heating, a common issue encountered during USW. The results indicate that the submerged ultrasonic welded (S-USWed) specimen with a semi-circular ED exhibits the highest weld strength, that is, 16.4 MPa compared to specimens welded via conventional USW technique using rectangular and triangular EDs achieving weld strength of 14.69 and 14.3 MPa.
The optimal mode for ultrasonic welding (USW) of the “PEEK–ED (PEEK)–prepreg (PEI impregnated CF fabric)–ED (PEEK)–PEEK” lap joint was determined by artificial neural network (ANN) simulation, based on the sample of the experimental data expanded with the expert data set. The experimental verification of the simulation results showed that mode 10 (t = 900 ms, P = 1.7 atm, τ = 2000 ms) ensured the high strength properties and preservation of the structural integrity of the carbon fiber fabric (CFF). Additionally, it showed that the “PEEK–CFF prepreg–PEEK” USW lap joint could be fabricated by the “multi-spot” USW method with the optimal mode 10, which can resist the load per cycle of 50 MPa (the bottom HCF level). The USW mode, determined by ANN simulation for the neat PEEK adherends, did not provide joining both particulate and laminated composite adherends with the CFF prepreg reinforcement. The USW lap joints could be formed when the USW durations (t) were significantly increased up to 1200 and 1600 ms, respectively. In this case, the elastic energy is transferred more efficiently to the welding zone through the upper adherend.
Thermoplastics hold utmost importance in the day-to-day life of modern-day society, being widely employed in water transport and storage vessels commonly made from thermoplastics such as PVC, i.e., polyvinyl chloride, and PP, i.e., polypropylene. This urge for a joining technique is applicable even with water in the vessel or the submerged case. The present investigation explores ultrasonic welding as an option to weld thermoplastics in water-submerged conditions. We have performed FEM simulations and experimental validation to prove the viability of the proposed ultrasonic welding process used in welding PVC and PP in water-submerged conditions. The discussed results demonstrate a decrease in melting and degradation of adherend material at the weld interface while welding PVC and PP in water-submerged conditions and attaining 65.78% and 107% of weld strength, unlike their open-air counterparts, respectively.
Ultrasonic consolidation (USC) of thermoplastic composites is a highly attractive and promising method to manufacture high-performance composites. This work focuses on USC of dry carbon fiber (CF) fabrics with high-temperature polyphenylene sulfide (PPS) films. Experimental trials to assess feasibility of the process are time-consuming. Consequently, a predictive thermal model would facilitate process parameters selection to reduce expensive trial-and-error approaches. This paper presents a 2D finite element model of samples under consolidation, incorporating equations for viscoelastic heating, matrix phase change, and material properties. Theoretical temperature profiles for nodes of interest were compared to the corresponding experimental temperature curves for various control parameters (i.e., weld time and vertical displacement of sonotrode) and showed good agreement during heating phase. It was found that welding time values below 1750 ms were insufficient to reach melting temperature, whereas weld times above 3000 ms led to the lowest average void content (2.43 ± 0.81 %). More specifically, the time the material spent above melting temperature, i.e., residence time, was established as a parameter that could estimate cases resulting in better consolidation and lower void content (time above 2600 ms for void content below 2.5%). XRD characterization revealed that the USC process led to mostly amorphous PPS, due to the high cooling rates (70 °C/s to 108 °C/s). Overall, the thermal model and micro-structural outcomes confirmed the feasibility of the USC process for layered composites made from dry fabric and high-temperature thermoplastic films.
This study analyzed the effects of hygrothermal conditions on the single-lap shear strength of a carbon fiber/poly-ether-ketone-ketone (CF/PEKK) thermoplastic composite material fabricated by induction welding. Specimens were exposed to an 85 °C/85% environment using a temperature and humidity chamber to identify the effect of moisture on single-lap shear strength, while their moisture saturation was assessed through weight measurement. Single-lap shear strength tests were performed on the dried and saturated specimens at 25 °C and 100 °C to 180 °C at 20 °C intervals. At 160 °C, the strength of the CF/PEKK thermoplastic composites rapidly declined to 76% (dried specimens) and 78% (moist specimens). The fracture surfaces and failure modes were analyzed using scanning electron microscopy images, which confirmed an increase in the degraded areas and naked fibers at higher testing temperatures. In addition, it was found that exposure to a moist environment changes the failure mode from fiber bundles and fiber/matrix failure to naked fiber and matrix failure owing to the reduction in interfacial adhesion properties. The findings confirmed that hygrothermal conditions directly affect the degradation of the CF/PEKK thermoplastic composites and that a rapid reduction in the single-lap shear strength occurs above Tg.
L’intérêt croissant de l’industrie aéronautique pour les matériaux composites favorise le développement de procédés de mise en œuvre rapides et automatisés. Technologie approuvée pour la réalisation de stratifiés à matrice thermodurcissable, les cellules de placement de fibres de la société Coriolis Composites permettent la fabrication de pièces stratifiées aux formes et dimensions variées. Ne nécessitant pas de polymérisation longue et onéreuse en autoclave tout en répondant aux nouvelles règlementations environnementales et aux besoins thermomécaniques spécifiques, les composites thermoplastiques sont une issue aux nouveaux enjeux du monde du transport. Le procédé s’appuie sur la technologie des lasers à diodes générant les densités de puissance nécessaires à la fusion des matrices thermoplastiques. Les travaux présentés s’inscrivent à la croisée de ces trois technologies en fort devenir : procédé de placement de fibres, matrice thermoplastique et laser à diodes. Ils sont menés dans le cadre du projet IMPALA (Innovation Matériaux et Procédés avec plAcement de fibres LAser) labellisé FUI 11, et, ont pour objectif de modéliser le procédé par l’expérimentation et la simulation. Le matériau composite étudié dans le cadre de cette thèse est l’APC-2/AS4 de la société Cytec Engineering Materials, pré-imprégné constitué de fibres de carbone et d’une matrice thermoplastique PEEK. Trois modèles numériques sont développés : (i) une modélisation optique fondée sur un algorithme de lancer de rayons permettant de déterminer la distribution du rayonnement laser sur la matière, (ii) une modélisation thermique renvoyant les champs de température au sein du stratifié en cours de drapage et (iii) une modélisation rhéologique afin d’étudier la déformation de la matière et la qualité du soudage des différents plis. Le développement de ces modèles s’appuie sur une caractérisation du procédé notamment du faisceau laser permettant la chauffe synchrone des fibres acheminées et des plis précédemment déposés et du module de compactage constitué d’un rouleau souple épousant la surface de drapage. Des données matériaux telles que les indices de réfractions, l’émissivité ou la viscosité sont également déterminées par voie expérimentale ou homogénéisation. En parallèle, des campagnes de mesures par thermocouples et radiométrie sont réalisées pour mieux comprendre les phénomènes thermiques dans la zone de chauffe et au sein du stratifié. Les confrontations entre ces mesures et les prédictions numériques renvoyant de bonnes corrélations, le modèle optico- thermique peut alors être exploité afin d’établir l’influence de différents paramètres sur le procédé et de proposer de solutions d’asservissement entre la puissance du laser et la vitesse de drapage. Enfin, une étude par spectroscopie infrarouge permet d’étendre une cinétique de dégradation du matériau au cas transitoire adapté au procédé de placement de fibres.
This paper presents details of the mechanical properties related to the static and fatigue strength of carbon fiber reinforced polyetherketoneketone (CF/PEKK) thermoplastic induction-welded composite joints. To better understand the process parameters, the finite element modeling (FEM) of the heat distribution was analyzed based on the generator power, coil coupling distance, coil moving speed, frequency, compaction force, and coil geometry while maintaining the optimal coil speed. The temperature behavior calculated using the simulation model exhibited good agreement with experimental results. A microscopic inspection, non-destructive test (NDT) was conducted to check the morphology characteristics of the welded joints. To check the mechanical performance of the induction-welded specimens, single-lap shear strength (SLSS) tests under static and cyclical fatigue loading conditions were conducted to check the weld qualities from a practical perspective. The mechanical testing results indicated that the static and cyclical fatigue specimens were dominated by a cohesive failure mode with a light fiber tear (LFT). These results suggested that using the optimal process parameters based on multi-physics FEM simulation could potentially improve mechanical performance.
The paper suggests an advanced method of computer-aided manufacturing of laminated variable cross-section products which allows to significantly expand possibilities for application of modern polymer composites. Results of the study can be used for manufacturing important aeronautical products. Interdependencies between main technological modes were studied. The paper shows that in order to deliver high quality products it is necessary to furnish optimal combination of airflow temperature, pressure, and speed of the nozzle relative movement.
Numerous studies in application of modern composite materials show that their advantages can be successfully implemented in manufacturing «smart» products. This study proposes an improved technological method of manufacturing multilayer environmentally friendly products with a variable cross section, which allows us to expand the possibilities of using modern polymer composite materials (PCM). The technology allows manufacturing products of the most complex geometric shapes, such as wind turbine blades. The aim of the study is the technological support of engineering production in the manufacture of multilayer products of variable cross section made from PCM. Scientific novelty consists in identifying the patterns of implementation and management of the manufacturing process of multilayer products of variable cross-section, and establishing the influence of structural and technological parameters of the manufacturing process on their operational characteristics. The relationship between the pressure of a hot directed air stream and the volume fraction of pores in the hardened material of a multilayer composite product with a variable cross section during layer-by-layer application is investigated. During the study, fundamental and applied principles of mechanical engineering technology, material resistance, adhesion theory, mathematical statistics tools and software were used to process the results of the experiment. Based on the results of laboratory studies, a methodology has been developed for effective prediction of pore content in the manufacturing of composite products. The introduction of the presented technology and the corresponding original methodology into production will reduce the complexity and energy costs of manufacturing composite products, improve their quality and reduce the impact of toxic components from composite materials on workers.
This paper proposes advanced manufacturing method of adhesive assembly of multilayer devices with variable cross-section that allows expanding possibilities for the use of modern polymer composite materials (PCM) in the manufacture of products of aerospace and aviation industry. We investigated the interrelation between pressure of directional hot air flow and pore volume fraction in solidified material of multilayer device of adhesive assembly with variable cross-section during layer-by-layer application. The methodology of efficient control of pore content during adhesive assembly of devices is developed on the basis of the results of laboratory studies.
This book offers a systematic overview of polymer joining and highlights the experimental and numerical work currently being pursued to devise possible strategies to overcome the technical issues. It also covers the fundamentals of polymers, the corresponding joining processes and related technologies. A chapter on the extrapolation of finite element analysis (FEA) for forecasting the deformation and temperature distribution during polymer joining is also included. Given its breadth of coverage, the book will be of great interest to researchers, engineers and practitioners whose work involves polymers.
Mechanical deformation of the plastics depends on the temperature, time and viscoelastic nature. The duration of the applied stress and the overall stress history are the stages dictating time dependency. Temperature dependent plastics deformation is affected by the thermal properties of the plastics which typically vary for thermoplastics and thermosets. Temperature dependency basically controls the time for plastic deformation. Semicrystalline or glassy plastics exhibits weaker viscoelastic nature at temperatures below their glass transition temperatures (Tg). It is essential to analyze the semicrystalline plastics for time-dependency based analysis owing to their nature. Increased mechanical response during time analysis is recorded due to the increased temperature either by heat provided during deformation or by the external heat fluxes. Plastics reveal significant difference in the deformation mechanism as compared to metals.
Amorphous (PC + ABS) polymers are welded using ultrasonic welding process which is the aim of this investigation. Polymer granules are molded into rectangular plates with energy director embedded onto it before welding of polymer specimens. Taguchi method is employed to design the welding parameters in this investigation. Differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) are performed to examine the thermal behavior of the welded specimens. Weld strength of the polymers is determined using the mechanical testing. Finite element and microscopical analysis are also reported in this study. In the end, RSM and ANOVA techniques are applied and presented.
Data acquisition (DAQ) is the key sequence in measurement of physical or an electrical phenomenon such as temperature, pressure, sound, voltage, or current using a computer. DAQ system (Fig. 5.1) comprises various sensors for appropriate applications, and the DAQ hardware is integrated with software to be viewed on computer. Compared to conventional measuring devices, computer-based DAQ devices employ the productivity, processing power, display, and connectivity abilities of industry standard computers offering more flexible, powerful, and inexpensive measurement solution.
Reinforced thermoplastic structural detail parts and assemblies are being developed to be included in current aeronautic programs. Thermoplastic composite technology intends to achieve improved properties and low cost processes. Welding of detail parts permits to obtain assemblies with weight reduction and cost saving. Currently, joining composite materials is a matter of intense research because traditional joining technologies are not directly transfer- able to composite structures. Fusion bonding and the use of thermoplastic as hot melt adhesives offer an alternative to mechanical fastening and thermosetting adhesive bonding. Fusion bonding technology, which originated from the thermoplastic polymer industry, has gained a new interest with the introduction of thermoplastic matrix composites, which are currently regarded as candidate for primary aircraft structures. This paper reviewed the state of the art of the welding technologies devised to aerospace industry, including the o elds that Universidade Estadual Paulista -~ lio de Mesquita Filho and Universidade de Sao Paulo are deeply involved.
Reinforced thermoplastic structural detail parts and assemblies are being developed to be included in
current aeronautic programs. Thermoplastic composite technology intends to achieve improved properties and low cost processes. Welding of detail parts permits to obtain assemblies with weight reduction and cost saving. Currently, joining composite materials is a matter of intense research because traditional joining technologies are not directly transferable to composite structures. Fusion bonding and the use of thermoplastic as hot melt adhesives offer an alternative to mechanical fastening and thermosetting adhesive bonding. Fusion bonding technology, which originated from the thermoplastic polymer industry, has gained a new interest with the introduction of thermoplastic matrix composites, which are currently regarded as candidate for primary aircraft structures. This paper reviews the state of the art of the welding technologies devised to aerospace industry, including the fields that Universidade Estadual Paulista Júlio de
Mesquita Filho and Universidade de São Paulo are deeply involved.
Joining of thermoplastic composites is an important step in the manufacturing of aerospace thermoplastic composite structures. Therefore, several joining methods for thermoplastic composite components have been under investigation and development. In general, joining of thermoplastic composites can be categorized into mechanical fastening, adhesive bonding, solvent bonding, co-consolidation, and fusion bonding or welding. Fusion bonding or welding has great potential for the joining, assembly, and repair of thermoplastic composite components and also offers many advantages over other joining techniques. The process of fusion-bonding involves heating and melting the polymer on the bond surfaces of the components and then pressing these surfaces together for polymer solidification and consolidation. The focus of this paper is to review the different fusion-bonding methods for thermoplastic composite components and present recent developments in this area. The various welding techniques and the corresponding manufacturing methodologies, the required equipment, the effects of processing parameters on weld performance and quality, the advantages/disadvantages of each technique, and the applications are described.
In filament winding of thermoplastics, localized melting/solidification can reduce the residual stresses and allow for improved dimensional stability and performance. This paper presents a three-dimensional thermal analysis for melting and consolidating impregnated tows in the presence of a local heat source during filament winding of thermoplastic composites. The analysis is performed using an Eulerian approach. The anisotropy of the filament wound woven structure is modeled as an orthotropic domain employing the concept of angle-ply sublaminates. The effective orthotropic conductivity tensor incorporates the effect of winding angle. The governing equations are discretized in a nonuniform mesh domain and solved using a finite difference approach. The processing parameters, such as winding angle, winding speed, and heat input, as well as material properties, are incorporated into the analysis. The results show large thermal gradients in the vicinity of the consolidation point. The effects of winding speed and heat input are investigated, and the overall thermal characterization of the process is discussed. The accuracy of the numerical method is assessed by comparing the results of a test problem with an available analytical solution.
An innovative methodology for the thermomechanical simulation of the infrared heating diaphragm forming (DF) process is proposed. In the first section of the paper, the heat transfer mechanisms between the infrared (IR) heating lamps and the thermoplastic plate are simulated, and the effect of the various preheating parameters on the heating time and temperature distribution is investigated. In the second section, the mechanical deformation of the thermoplastic component is simulated to enable prediction of heat losses due to the plate contact with the mold. Based on the developed simulation methodology, the main process parameters – e.g., the number, location, and power of IR lamps for optimal preheating; the heat losses during plate deformation; and the minimum required mold temperature throughout the forming phase – are derived for five different thicknesses. The optimization results show that the forming parameters considered influence the heating of the plate in a complex and interactive way; in addition, it is found that with increasing plate thickness, the heating time required to reach the desired temperature also increases.
The in-situ thermoplastic composite filament winding process employs a localized, on-line, and continuous meltings/solidification techniques which can reduce the residual stresses and allow for improved dimensional stability and performance. During the processing of thermoplastic composite materials, thermal expansion and crystallization shrinkage strains contribute to changes in the material specific volume and represent important sources of internal loadings/stresses. This work employs three-dimensional anisotropic thermal and stress analyses to present the effects of winding angle and matrix modulus on the effective coefficient of thermal expansion as well as process-induced stresses and deformations of the parts during in-situ filament winding of a thermoplastic composite, APC-2. The results show that the processing parameters have significant effects on the material responses of the parts being wound using this manufacturing technique.
The LIS (laser induced welding) process allows laser transmission welding of components which may exhibit localised joint gaps. In the joint gap region the melting mass of the absorbent joint part undergoes additional volume expansion as a result of foaming and comes into contact with the transparent joining partner fusing its surface and forming the weld joint, even if larger clearances (up to about 0.35 mm) exist. The additives for the LIS process are a new development and round out the range of Fabulase agents for laser welding and marking. The LIS process was originally developed by Chemische Fabrik Budenheim KG for laser marking to generate embossed structures (e. g. Braille or decors) on plastic surfaces. The cooperation with Techno- Scriptum and Fraunhofer ILT finally made it possible to extend and optimise this technique for laser transmission welding applications.
This study assesses the use of infrared welding for a carbon fabric reinforced polyphenylene sulphide. Infrared light is used is to melt the thermoplastic matrix of the two components, after which they are joined together under pressure. Welding parameters such as power of the infrared lights, heating time, contact pressure and consolidation time are optimised. Next, a series of joints is fabricated and the interlaminar behaviour of the weld is characterised by Lap Shear tests. It can be concluded that the infrared process proves very interesting for the material under study and that high quality joints can be manufactured with reproducible strength.
Thermoplastic elastomers are one of the most in-demand groups of materials today. This unique reference work compiles in one place the current working knowledge of chemistry, processing, physical, and mechanical properties, as well as applications of thermoplastic elastomers. © 2007 William Andrew Inc. Published by Elsevier Inc. All rights reserved.
Advanced composite materials were introduced in a unidirectional tape form in the early 1960's. A few years later, automated tape layers were conceived as a means to automate the process for laying up this new material form. The original versions of automated tape layers were home-built by aerospace companies in collaboration with material suppliers. The first computer numerical controlled (CNC) gantry tape layer was developed under an Air Force Materials Lab (AFML) program by General Dynamics and Conrac Corporation. From this origin, automated tape layer technology was developed to become the most widely used automated process for fabrication of large composite structures. Current tape layer technology is significantly improved over the original versions and offer more flexibility in process capabilities required for a wider variety of aerospace components. Aerospace industry tape laying applications are currently achieving impressive material lay up rates that help reduce the manufacturing cost of larg e composite structures. As the percentage of composite components on newer aircraft increases, new and innovative applications for tape layers are being defined. This paper includes information on current tape layer technology and examples of current tape layer production parts.
The on-line consolidation of thermoplastic composites is a relatively new technology that can be used to manufacture composite parts with complex geometries. The localized melting/solidification technique employed in this process can reduce the residual stresses and allow for improved dimensional stability and performance. An additional advantage of this technique is elimination of the curing steps that are necessary in the processing of thermoset-matrix composites. This paper discusses analytical and numerical anisotropic thermal analysis for preheating and/or pultrusion of impregnated composite tows or tapes. Heat of melting/solidification is included in the form of a heat generation term. A separation of variable method is employed to solve the governing equations analytically. In the numerical analysis, the governing equations are discretized using a nonuniform mesh and solved employing a finite difference approach. The processing parameters, such as processing speed, heat intensity, heat source width, etc., as well as material properties are incorporated in the analysis. The maximum error between the analytical solution and the numerical result is found to be 1%.
Recycled thermoplastic powder impregnated composites using in-situ filament winding and on-line consolidation of fibers have been successfully manufactured with the modified filament winding setup constructed in this study. Reclaimed low density polyethylene (RLDPE), reclaimed low-density polyethylene with polymer additives consisting of 0.25% by weight of Cyasorb® UV-3346 Light Stabilizer, 0.25% by weight of Cyasorb® UV-53 1 Light Stabilizer, and 0.08% by weight of Cyanox® 2777 Antioxidant (RLDPE-PA), and virgin low-density polyethylene (LDPE) were pulverized to ultrafine powders ranging from 20 to 300,um, and utilized to impregnate a separated fiberglass tow. After initial experiments, two powder-impregnated composite tubes were manufactured for each thermoplastic material system. The composites were then tested for tensile (hoop) strength and compressive bending strength under the ASTM D2290-95 and C-ring tests, respectively. This study showed that while the RLDPE composite did not perform well, composite samples made with RLDPE and polymer additives (i.e.. RLDPE-PA) performed better than RLDPE samples but not as well as composites made of virgin LDPE.
The impregnation and consolidation steps in the manufacturing process were also effective for all three systems. The composite tubes exhibited very low void contents and high fiber volume fractions, while unmelted and unconsolidated thermoplastic powders were not present in the manufactured parts. The absence of fiber waviness and fiber migration through the thickness of the composite demonstrates that the online consolidation of powder-impregnated fibers was also effective. The collection of the separated powder-impregnated fibers prior to filament winding also seemed to be sufficient.
The on-line consolidation of thermoplastic composites is a relatively new technology that can be used to manufacture composite parts with complex geometries. The localized melting/solidification technique employed in this process can reduce the residual stresses and allow for improved dimensional stability and performance. An additional advantage of this technique is the elimination of the curing steps which are necessary in the processing of thermoset-matrix composites. This article presents the effects of processing parameters on processability in on-line consolidation of thermoplastic composites for tape-laying and filament-winding processes employing anisotropic thermal analyses. The results show that the heater size, preheating conditions, and tow thickness can significantly affect the processing window which, in turn, affects the production rate and the quality of the parts.
The use of laser light for bonding of continuous fiber reinforced thermoplastic composites (CFTPC) offers new possibilities to overcome the constraints of conventional joining technologies. Laser bonding is environmentally friendly as no chemical additive or glue is necessary. Accuracy and flexibility of the laser process as well as the quality of the weld seams provide benefits which are already used in many industrial applications. Laser transmission welding has already been introduced in manufacturing of short fiber thermoplastic composites. The laser replaces hot air in tapelaying systems for pre-preg carbon fiber placement. The paper provides an overview concerning the technical basics of the joining process and outline some material inherent characteristics to be considered when using continuous glass fiber reinforced composites The technical feasibility and the mechanical characterization of laser bonded CFTPC are demonstrated. The influence of the different layer configurations on the laser interaction with the material is investigated and the dependency on the mechanical strength of the weld seem is analyzed. The results show that the laser provides an alternative joining technique and offers new perspectives to assemble structural components emerging in automotive or aeronautical manufacturing. It overcomes the environmental and technical difficulties related to existing gluing processes.
The mechanical performance of APC-2/AS4 thermoplastic composite C-ring samples with different processing conditions was investigated, and experimental results were compared with numerical results using finite element methods (FEMs). Mandrel/substrate preheating was found to be necessary for good-quality parts. Ten sets of samples, with five samples per set, were manufactured using in-situ thermoplastic composite filament winding. For the first five sets, tape preheated to below the glass transition temperature (Tg) at 110°C was used, while the consolidation pressure for various sets was 5.5, 12.6, 19.4, 26.0, and 32.4 kN/linear-meter. The same pressures were used for the next five sets while the tape was preheated above the Tg at 170°C. Scanning electron microscopy (SEM) was used for quality control. C-ring tests were performed to evaluate failure stress, strain, and deflection of C-rings at room temperature. Samples failed in compression at ring mid-section and inner radius. Samples made with 12.6 and 19.4 kN/linear-meter consolidation pressures yielded the best results. Non-linear FEM was employed to simulate the C-ring experiment using shell, target, and contact elements. The experimental deflection to failure was applied to the model, and the failure stress, strain, and load were determined. The results from non-linear numerical analysis were slightly higher than those determined from available analytical solution.
This paper presents analytical and numerical thermal analysis for melting and consolidating impregnated composite tapes in the presence of a localized heat source. This analysis also leads to the prediction of the processing window for a given tape-laying configuration. Heat of melting/solidification is included in the form of a heat-generation term. A separation of variables method is employed to solve the governing equations analytically. In the numerical analysis, the governing equations are discretized using a nonuniform mesh and are solved using a finite difference approach. The results show large thermal gradients in the vicinity of the consolidation point. The error between the analytical solution and the numerical result is found to be 3 percent for the maximum temperature, and the maximum error for the temperature over the entire domain is observed to be 7 percent. The effects of processing speed, heat intensity, and the width of the local heat source are investigated, and the overall optimization of the process is discussed. 22 refs.
Automated fiber placement allows precision fabrication of complex composite structures, but significant thickness reduction may occur during cure due to the presence of voids and excess resin in fiber placed parts. Zero-bleed toughened epoxy resin systems required for many aerospace applications (including Cytec 977 or Hexcel 8552) are particularly difficult to debulk, and hot vacuum bag debulking or interim autoclave processing are widely used with these materials to avoid fiber wrinkling (marcelling). Foster-Miller's Ultrasonic Tape Lamination (UTL) is a highly effective debulking method, capable of providing net thickness as-placed parts. UTL induces virtually instantaneous viscoelastic and frictional heating and intra-ply nesting. In- situ debulking and controlled staging of thermoset prepreg can be achieved through the use of closed loop temperature control and advanced process modeling. Used in conjunction with E Beam curing or novel thermal techniques, such as solid state postcure, UTL provides an avenue for out-of-autoclave curing of high quality fiber placed structures. This approach offers the possibility of out-of-autoclave processing without the development and qualification of new resin formulations. This paper covers the development of UTL for in-situ debulking and staging. It also includes a discussion of viscoelastic materials characterization and process modeling for carbon fiber/Hexcel 8552 thermoset prepreg.
An experimental investigation of a novel approach for manufacturing of thermoplastic matrix composites, is described. The technique is based on using laser energy as the focused heat source to melt the matrix material for subsequent consolidation, and appears to be particularly suited for thermoplastic filament winding opertions. An experimental set up is defined to produce multi ply rings, and the feasibility of this technique is demonstrated by discussing several samples that were produced using Ryton AC40-60 prepreg tapes. The quality of consolidation is examined through cross-sectional micrographs. 12 references.
Ultrasonic welding is considered as one of the most promising welding techniques for continuous fiber-reinforced thermoplastic composites. Intermolecular friction within the bulk, resulting from the application of ultrasonic waves applied on the surfaces, generates the heat required for welding to take place at the interface of the joining members via the so-called “energy directors” (EDs). Energy directors consist of resin protrusions or artificially produced asperities on the composite surfaces and play an important role both in the welding process and in the quality of the resulting welds. This paper presents the results of a study on the effects of configuration of different EDs on the ultrasonic welding of carbon fiber/polyetherimide advanced thermoplastic composites in a near-field setup. Triangular EDs were molded on the surface of consolidated composite laminates with a hot platen press. Single lap-shear-welded samples were produced to investigate the influence of the orientation of the EDs with respect to the load direction, as well as the configuration of multiple EDs. The results indicate that the configuration of multiple transverse EDs was more effective in covering the overlap area, once the resin has melted, causing only a minimum fiber disruption at the welding interface. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:112–121, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20178
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