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Finite element modeling of polymer curing in natural fiber reinforced composites

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Abstract

Plant-based fibers have been selected as suitable reinforcements for composites due to their good mechanical performances and environmental advantages. This paper describes the development of a simulation procedure to predict the temperature profile and the curing behavior of the hemp fiber/thermoset composite during the molding process. The governing equations for the non-linear transient heat transfer and the resin cure kinetics were presented. A general purpose multiphysics finite element package was employed. The procedure was applied to simulate one-dimensional and three-dimensional models. Experiments were carried out to verify the simulated results. Experimental data shows that the simulation procedure is numerically valid and stable, and it can provide reasonably accurate predictions. The numerical simulation was performed for a three-dimensional complex geometry of an automotive part to predict the temperature distribution and the curing behavior of the composite during the molding process.

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... Bessel functions with the order of ν K r Conductivity ratio = k 011 k 022 dimensionless k oxx , k o , k ox Off-axis conductivity coefficients at reference temperature ( W m −1 K −1 ) k xx , k , k x Off-axis conduction coefficients ( W m −1 K −1 ) k 011 , k 022 On-axis conductivity coefficients at reference temperature ( W m −1 K −1 ) k 11 , k 22 On-axis conduction coefficients ( W m Mass function x, Spatial variables of the coordinate system (0 ≤ x ≤ l, − ≤ ≤ ) ...
... Although many investigations have been established on the mechanical properties of these materials [5][6][7][8][9], there are few studies available that investigate their heat transfer behaviors. The investigation of the heat transfer phenomenon in fibrous composites yields useful information in fiber placement analysis [10][11][12], thermal stress studies, thermal shock prevention, and thermal fracture analysis [13][14][15][16][17], as well as controlling the directional heat transfer process [18]. Properties of fibrous composites are usually changed with the fiber direction, which creates many complications in structural equations and analytical methods [19]. ...
... To solve PDE (11), an FIT with respect to is applied. The general forms of the FIT with respect to and its inverse are shown in Eqs. ...
Article
The present study proposes an exact analysis for unsteady anisotropic conduction heat transfer in heterogeneous composite conical shells. The fibers in the composite conical shell are wound in arbitrary directions so that a defined fiber angle changes between 0° and 90°. The cone’s base is considered to have a general linear boundary condition, while the effects of internal heat generation, thermal convection, and external radiation heat flux on the temperature distribution are investigated. The heterogeneity of the heat transfer problem is caused by a linear dependence of conduction coefficients on the temperature. To solve the governing equations, first, the Kirchhoff transformation followed by an appropriate finite integral transform is applied. The resulting nonhomogeneous equation is then separated into two equations, i.e., steady equation and unsteady equation. The solution of the steady case is derived using Green’s function, while the separation of variables method is utilized to solve the unsteady part. Eventually, the temperature distribution is achieved by applying the inverse transforms on the subsequent solutions. The verification of this solution is based on the comparison between the present analytical results and numerical computations with a second-order finite difference code. Applicability of the present solution is evaluated for resolving an industrial case problem.
... The technique of modelling and numerical simulation has been applied in the study of manufacturing processes of different types of materials [6][7][8][9][10][11][12][13]. The principal aim of these works is studying the allowance of using new tools that can help in the optimization of processing parameters to a specific material. ...
... The wood agglomerates are probably one of the areas with more knowledge about this thematic [7,8]. Besides wood agglomerates, wood plastic composites (WPC) and other composites were the object of study by other researchers [6,9,12]. Regarding composites, one factor to add to the development time of new materials is the diversity of combinations between variables related to its composition -like matrix, fillers and other additives. ...
... This model is constituted by two arms, one of which has three thermal resistances in series (1) and another one where the same resistances are arranged in parallel (2). Once the heat flux through an association in series is equal to the one across every resistance, the equivalent thermal conduction coefficient is calculated by Eq. (9). For the association, in parallel, the value of the coefficient is determined by Eq. (10). ...
Article
Cork-based composites result from a combination of cork granules with different materials – like thermosets or thermoplastics – and its manufacture involves a thermal process. In order to simulate the manufacturing process, of these types of composites, a new methodology was applied. A material composed of cork and a thermoplastic served as a case study. A model for the prediction of a cork composite mixture properties and a simulation methodology were developed for studying the variation of temperature during the moulding process of cork composites. Density, thermal conductivity, and specific heat were determined based on the formulation of the composite and the properties of cork and the agglutinant agent. Numerical analyses were carried out and compared to experimental results obtained from a moulding process. Three types of simulations, according to the model of the chosen properties were developed using finite volume and finite element methods. In general, the results from the simulations were in good agreement with experimental results.
... The prediction of the molding state of carbon fiber reinforced polymers (CFRPs) by numerical simulation is considered effective for establishing a method to mold high-quality composite materials [1,2,3], which in turn requires accurate modeling of the thermal behavior and an understanding of the model parameters. However, given the numerous types of resins and the problem of resin aging, high-precision estimation using only numerical simulations is difficult [4]. ...
... The curing reactions of the thermosetting resin are expressed as curing rules using the equations of the Kamal and Sourour model and the Arrhenius equation, as shown in Eqs. (3) and (4) [30]. ...
Article
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The models and parameters related to the generated curing heat in the molding simulation of composite materials are dependent on the type of resin used and the experimental conditions. Therefore, in this study, we estimated the generated curing heat that changes with time by a data assimilation method, which combines the observation values with simulation values, so that the heat curing simulation of carbon fiber reinforced polymers (CFRPs) becomes closer to the experimental conditions. In the data assimilation method, the temperature distribution on the surface of the composite material was used as an observation value, and the generated curing heat was estimated using an ensemble Kalman filter. By optimizing the data assimilation parameters in advance using the response surface method and estimating the generated curing heat by numerical experiments, the generated curing heat could be estimated with an accuracy represented by the time mean error of less than 6%.
... So it is necessary to rigorously control all the processing variables to improve product quality and to optimise pressing time. Hence, it is highly viable to improve the quality of WPC, for which important aspects of proper curing of matrix and manufacturing of the composite materials should be taken into consideration 10 . Compression moulding seems a fairly simple manufacturing process however it can be quite difficult to visualize the mechanism happening inside the material during the pressing 7,11 , failure to understand can lead to weak strength and quality issues in the final product and rejection of the end product. ...
... Thus, in order to gain insight, simulation software have been proven to be helpful in visualizing the effects of temperature and curing of matrix inside the board 7,19,20 . Hence, in order to improve the quality of WPC, the important aspects of proper curing of matrix and manufacturing of the composite materials should be taken into consideration 10 . Furthermore to reduce the wastage in industries and laboratories, computer modeling and simulation was suggested as a reliable approach to assist scientist in exploring the parameter space 7,11,17 . ...
Article
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Objectives: This paper presents a review on the application of simulation software as a tool aiding in design and manufacturing aspect of wood plastic composites (WPCs). The scope of application of models present in literature by previous researchers is discussed in general. Methods/Statistical Analysis: A review on the simulation in wood plastic composites manufactured by compression moulding process is presented by analyzing the data present in literature. Important factors which affect the mechanical properties of final wood plastic composite products are stated. This paper also addresses the challenges of application of simulation models for prediction of mechanical properties of wood plastic composites by other researchers. Findings: Simulation models related to wood based composites are discussed and their applicability for wood plastic composites is reported. A need of simulation software for WPC prediction purpose and easy to use by other researchers is highlighted. Application/Improvements: Importance of collaborative efforts between material researchers and computer science researchers is also highlighted to fulfill the need of the simulation software in wood plastic composite area.
... Composite density can be obtained by rule of mixture (12): ...
... V f is the volume fraction of fiber. Similarly, using the rule of mixture, the specific heat of composite can be evaluated (12): ...
Article
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Key thermophysical properties of the thermosetting resin, including density, conductivity coefficient and specific heat that evolve with resin curing, are related to temperature and curing degree fields of the fiber/resin composite material. However, their effects on heat transfer inside composite materials, consequently on the curing non-uniformity in thick-section laminates, are not well understood. The focus of this study is on the effects of key thermophysical properties of resin on the curing uniformity of AS4/3501-6 composite by means of the coupled thermochemical analysis with the method of numerical simulation. The results clearly indicate that the conductivity coefficient and specific heat of resin have obvious influence on curing uniformity, especially for thick laminates, while the density of resin has no noticeable effect on the curing uniformity. The simulation results can help to guide the material preparation of industrial production.
... Different modelling and optimization methods of natural fiber composites include finite element analysis (FEA) [29][30][31], artificial neural networks (ANN) [28,29], and rule of hybrid mixture (RoHM) [31][32][33][34]. Numerous literatures are available on the utilization of computational techniques in the modeling and optimization of composite materials in the field of science and engineering. ...
... Different modelling and optimization methods of natural fiber composites include finite element analysis (FEA) [29][30][31], artificial neural networks (ANN) [28,29], and rule of hybrid mixture (RoHM) [31][32][33][34]. Numerous literatures are available on the utilization of computational techniques in the modeling and optimization of composite materials in the field of science and engineering. ...
Article
Full-text available
The study of natural fiber-based composites through the use of computational techniques for modelling and optimizing their properties has emerged as a fast-growing approach in recent years. Ecological concerns associated with synthetic fibers have made the utilisation of natural fibers as a reinforcing material in composites a popular approach. Computational techniques have become an important tool in the hands of many researchers to model and analyze the characteristics that influence the mechanical properties of natural fiber composites. This recent trend has led to the development of many advanced computational techniques and software for a profound understanding of the characteristics and performance behavior of composite materials reinforced with natural fibers. The large variations in the characteristics of natural fiber-based composites present a great challenge, which has led to the development of many computational techniques for composite materials analysis. This review seeks to infer, from conventional to contemporary sources, the computational techniques used in modelling, analyzing, and optimizing the mechanical characteristics of natural fiber reinforced composite materials
... Mitani et al. (2005) presented only a one-dimensional model using finite difference (FD) method to predict the temperature distribution and cure behavior of natural fiber composites in the RTM process. While A non-linear heat transfer analysis combined with a cure kinetic model based on finite element procedures was developed by Behzad (2007), using hemp fiber/thermoset composite, three-dimensional mode was developed for a simple block of the composite and compared with experimental results. Experimental data shows that the simulation procedure is numerically valid and stable (Behzad & Sain, 2007). ...
... While A non-linear heat transfer analysis combined with a cure kinetic model based on finite element procedures was developed by Behzad (2007), using hemp fiber/thermoset composite, three-dimensional mode was developed for a simple block of the composite and compared with experimental results. Experimental data shows that the simulation procedure is numerically valid and stable (Behzad & Sain, 2007). ...
... Waste such as sunflower, rice, wheat husk, wood fiber was developed with chemical binders and their applications in residential and other buildings were reported (Binici et al. 2014). Hemp fibers (0.115 W/mK) (Behzad and Sain 2007), corn stalk (0.1999-0.1 W/mK) (Binici, Aksogan, and Demirhan 2016), Banana fiber, and PL composites (0.0183 to 0.03168 W/mK) (Gehad R. Mohamed et al. 2021), rice straw (0.051-0.053 W/mK) (Wei et al. 2015), Agave fiber and wheat straw composites (0.04455-0.06835 ...
... in composite materials flourished multiple times; it began for their applications to new materials in multiple fields, such as aerospace engineering [19], civil engineering [38], and materials science [6,36]. ...
Preprint
Fiber reinforced materials (FRMs) can be modeled as bi-phasic materials, where different constitutive behaviors are associated with different phases. The numerical study of FRMs through a full geometrical resolution of the two phases is often computationally infeasible, and therefore most works on the subject resort to homogenization theory, and exploit strong regularity assumptions on the fibers distribution. Both approaches fall short in intermediate regimes where lack of regularity does not justify a homogenized approach, and when the fiber geometry or their numerosity render the fully resolved problem numerically intractable. In this paper, we propose a distributed Lagrange multiplier approach, where the effect of the fibers is superimposed on a background isotropic material through an independent description of the fibers. The two phases are coupled through a constraint condition, opening the way for intricate fiber-bulk couplings as well as allowing complex geometries with no alignment requirements between the discretisation of the background elastic matrix and the fibers. We analyze both a full order coupling, where the elastic matrix is coupled with fibers that have a finite thickness, as well as a reduced order model, where the position of their centerline uniquely determines the fibers. Well posedness, existence, and uniquess of solutions are shown both for the continuous models, and for the finite element discretizations. We validate our approach against the models derived by the rule of mixtures, and by the Halpin-Tsai formulation.
... Chemical modifications are very much required to customize the fiber interface. Behzad and Sain [9], proposed a variety of mechanisms for the coupling of materials, namely: (i) the removal of poor boundary layers; (ii) the construction of a difficult and flexible layer; (iii) the forming valence bonds between each materials; (iv) the enhancement of wetting among substrate and polymer; (v) Construction of an exceptionally cross-linked interphase zone with a modulus intermediate between the substrate and the polymer; (vi) Surface substratum acidity transition. A number of researchers have studied Chemical alteration of natural fibers to maximize conformity to the polymer matrix [10]. ...
Article
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The primary aim of this study is to develop a biocomposite by using biopolymer and natural fibers/particles from renewable resources. With the aid of poly-condensation process, the cardanol thermoset biopolymer resin from cashew nut shell liquid (CNSL) was synthesized. The abundantly available, bagasse fiber (20 mm of length) and coconut shell particle (50 μm) were applied as reinforcement material to produce a new ecological hybrid biocomposite. The prepared fiber and particles are treated chemically. Hybrid composites of Cardanol (C) reinforced with bagasse fiber (BF), Coconut shell powder (CP) and Bagasse fiber/Coconut shell powder (BC) were manufactured using a compression moulding process. This four different kinds of composites, though the sequences are done to have C, C/BF, C/CP, and C/BC. The mechanical properties of the prepared biocomposites were evaluated through tensile, flexural and impact test. These evaluation predicts that C/BF possess comparatively more strength with other hybrid composites. The presence of fiber and particle are attributed in all the biocomposites using FT-IR spectroscopy analysis. Similarly during thermal analysis, C/BF corroborate with higher thermal stability than other biocomposites by thermal gravimetric analysis.
... Thus, heat transfer analyses are absolutely useful for manufacturing and exploitation processes of composite structures. In particular, study of anisotropic heat conduction in composite materials is of high importance in the manufacturing purposes [1][2][3], thermal stress analysis [4][5][6][7][8], and temperature control of heterogeneous composites. ...
Article
In present paper, problem of anisotropic heat conduction in heterogeneous composite conical shells is solved analytically. Arbitrary values for fiber angle (ranging from zero to 90 degrees) cause anisotropy for the heat conduction problem in composite conical shells. In our analysis, heat convection between conical shell and ambient flow is taken into account. In addition, an external source of radiative heat transfer is modeled. Herein, the heat conduction problem is assumed to be heterogeneous which is due to dependence of the conductivity coefficient on temperature. Kirchhoff transformation followed by an integral transform method are used to solve present heterogeneous heat conduction problem. Green’s functions are applied to find the solution of final ordinary differential equations. Verification of the present analytical solution is obtained through comparing the analytical results with those of a second order finite difference method. Good agreement between the analytical and numerical results has been found. In order to evaluate the capability of our analytical solution in solving real industrial problems, the temperature distributions in a typical pressure vessel and a pin fin are calculated.
... The density of AS4 fiber q f is 1790 kg/m 3 [2]. The specific heat C f and the thermal conductivity k f of AS4 fiber both increase linearly with temperature [23]: ...
Article
Full-text available
A multi-field coupled model was developed to simulate the flow–compaction behavior of thick composite laminates manufactured by the autoclave process based on Darcy’s law and the effective compaction stress theory. The model was verified by comparing the predictions with the experiment results of a thick unidirectional laminate. The results show that the resin flow and compaction of fiber bed start from the top surface and gradually spread into the interior region, and the non-uniform resin flow along the thickness direction causes a gradient distribution of fiber volume fraction in the thick composite part. A cross-plied composite laminate model with a thin interlaminar layer was constructed, and the effect of the interlaminar transverse permeability on the flow–compaction behavior of the thick cross-plied laminate was numerically analyzed. The results indicate that the thick cross-plied composite laminate with high interlaminar transverse permeability has the similar flow–compaction process with that of the thick unidirectional laminate. An interlaminar layer with low transverse permeability impedes the resin flowing out from the interior of the thick cross-plied composite laminate and causes a lower fiber volume fraction compared with that in a unidirectional laminate. © 2018 Springer Science+Business Media, LLC, part of Springer Nature
... In contrast to mechanical properties of composite materials, their heat transfer behavior has been less studied [1][2][3][4][5][6][7]. Study on the heat transfer phenomena in composite materials provides valuable knowledge in many other applications such as analyzing fiber placement in the production process [8][9][10], preventing thermal fracture [11][12][13] and controlling the directional heat transfer in laminates. ...
Article
In the present paper, a general analytical solution is proposed for anisotropic heat conduction through truncated composite spherical shells. The solution is so important in designing the spherical vessels which are usually used to store the CNG, LNG, LPG and other petroleum condensates. Herein, it is supposed that the fiber angle of composite laminate is in range of zero to 90 degrees. Heat convection with ambient flow, an external heat radiation, and a possible internal heat generation are modeled within the heat transfer equation. The exact solution is derived using the complex finite Fourier transform method. The particular solution of transferred equation is found based on the Green’s function and Sturm-Liouville theories. Finally, an inverse integral transformation is applied to form the final analytical solution in physical space. Defining four materials differing in the value of conductivity coefficient in fiber direction, the effects of used composite material and fiber angle on temperature distribution of the spherical shell are investigated in detail.
... Ignoring the effect of polymer flow in the material, the term can be directly related to the rate of cure degree qa=qt by the following equation. 42,43 qQ cure qt ¼ qH r qa qt (15) where q is the density of the resin and H r is the total heat of reaction. ...
... In recent years, intense research and development has been conducted on the devel- opment of methods to manufacture inexpensive, high-quality, and stable composite materials using a new technique called 'out of autoclave,' which was proposed to solve the aforementioned issues. Among the new alternatives, a method that determines the internal state of the composite material being molded to set the process conditions has been considered effective, which has led to a series of studies related to state estimation using numerical simulations [3][4][5][6]. However, owing to the nonuniformity of thermal *Corresponding author. ...
Article
Monitoring methods used to observe the molding process of carbon fiber-reinforced plastic (CFRP) facilitate the development of high-quality products. However, current monitoring methods provide only localized state information, and estimating the state of the entire material is difficult. This study proposes a method for estimating the overall state of CFRP during molding based on data assimilation, which integrates theoretical and experimental values. In this method, three types of specimens with different thermal conductivities were considered, and the temperatures throughout each specimen during molding were estimated by data assimilation of surface temperatures measured using thermocouples. To validate the accuracy of this method, the temperatures estimated by data assimilation were compared with those obtained using numerical simulations without data assimilation. The experimental results of all the specimens showed that data assimilation can be used to accurately estimate the surface temperature. The proposed method is therefore effective for monitoring composite molding processes.
... In order to produce high-quality carbon fiber-reinforced plastics (CFRP), CFRP molding state prediction via numerical simulations is considered an efficient method [1,2,3]. Predicting the CFRP molding state requires accurate modeling and understanding of the thermal behavior [4]. ...
Article
Full-text available
Accurate simulations of carbon fiber-reinforced plastic (CFRP) molding are vital for the development of high-quality products. However, such simulations are challenging and previous attempts to improve the accuracy of simulations by incorporating the data acquired from mold monitoring have not been completely successful. Therefore, in the present study, we developed a method to accurately predict various CFRP thermoset molding characteristics based on data assimilation, a process that combines theoretical and experimental values. The degree of cure as well as temperature and thermal conductivity distributions during the molding process were estimated using both temperature data and numerical simulations. An initial numerical experiment demonstrated that the internal mold state could be determined solely from the surface temperature values. A subsequent numerical experiment to validate this method showed that estimations based on surface temperatures were highly accurate in the case of degree of cure and internal temperature, although predictions of thermal conductivity were more difficult.
... The density was taken from the DGEBA resin, with a value of 1168 kg m -3 , and for the thermal conductivity, a constant theoretical value of 0.2 W m -1 K -1 was considered since it appears that the slight change of thermal conductivity with temperature has negligible effects on the thermal model [31][32][33]. Concerning the C p , the variation of the heat capacity with the conversion degree and the reaction temperature was obtained by DSC and included in the thermal model [34,35]. ...
Article
Full-text available
A thermo-kinetic model was employed to study the temperature and curing degree distribution in a casting part of a DGEBA–DDM system during its curing process in an oven. Initially, the curing of the DGEBA–DDM casting part system was investigated by isothermal and non-isothermal differential scanning calorimetry. A Kamal and Sourour phenomenological model expanded by a diffusion factor was proposed for modeling the curing. The proposed model fit properly the curing behavior of this system in the analyzed range of temperatures. This model enables the application within finite element analysis software for modeling the curing process of real thermosetting parts. Finite element-based program COMSOL Multiphysics™ was used to simulate the curing process. The model fits properly the initial heating of the sample until the reaction temperature, the time position at which the temperature starts to increase due to the heat generated during epoxy–amine reaction and also the rate at which the temperature increases, but it overestimates the maximum temperatures reached in the system. Nevertheless, the proposed model is shown as a powerful tool to design optimal curing cycles for thermosetting resins avoiding temperatures closer to the degradation temperature of the system and avoiding significant temperature gradients inside the sample.
... Chemo-physical analyses of the epoxy resin, such as rheology and cure kinetics, were thus given in advance to understand the experimental better [21][22][23][24][25][26][27][28][29] . ...
Article
A comprehensive understanding of strain history in resin matrix composite, which is caused by variability of thermo-mechanical properties of the resin during composite processing, is essential to allow better design and control of properties of the resin matrix composite. In this paper, to know strain history of fast curing epoxy matrix composite and differences of strain history between fast and conventional curing epoxy matrix composites well, temperature and strain history at different locations in ten-ply unidirectional carbon-fiber fabrics reinforced the fast and conventional curing epoxy matrix composite laminates manufactured by wet lay-up method were measured by fiber Bragg grating (FBG) sensors. Results shown that the peak temperature due to curing exothermal reaction was 133.7 °C in both the 1st ply and the 5th ply in the fast curing composite when cure temperature profile settled at 80 °C, which was 27.4 °C higher than that in the conventional curing composite. Cure residual strain in the 1st ply and the 5th ply in the fast curing composite were −5183.3 με and −4074.7 με, respectively; while they were −2975.9 με and −2660.8 με in the conventional curing composite. The related properties of rheology and cure kinetics of the epoxy resin were thus given in advance.
... Il faut néanmoins noter que ces études ne sont que très partielles et qu'elles ne donnent par exemple pas d'indications sur l'évolution de la microstructure du renfort fibreux à l'échelle des fibres. Il faut approfondir ces points pour aboutir à la constitution de modèles rhéologiques et thermocinétiques fiables (Behzad et Sain, 2007) pour ces matériaux. ...
... Because of these features, they are used in piping, heat exchangers, cooling systems[1][2][3], latent heat thermal energy storage systems[2,[4][5][6], aerospace components, fluid reservoirs, pressure vessels, sport and medical equipment and so on. Solutions of heat conduction in composite materials provide beneficial knowledge for preventing thermal fracture[7][8][9], analyzing fiber placement in production process[10][11][12]and controlling the directional heat transfer in the laminates. Most of previous works dealt with heat conduction in composite materials presented numerical or semi-analytical solutions and few exact analytical solutions were presented in literature. ...
Article
This paper presents an exact analytical solution for transient anisotropic heat conduction in a truncated composite conical shell for the first time. The fibers of composite conical shell are winded around the body in any arbitrary direction. Heat convection between the ambient fluid flow and composite conical shell is modeled and the exact solution of heat conduction equation is obtained by combining two popular analytical methods. First, by means of an integral transform in angular direction, the heat conduction equation is transformed and after that the transferred heat equation is solved using separation of variables method. Eventually, an inverse transformation is used in order to achieve the final exact solution of heat conduction equation. Validation of the present analytical solution is performed by comparing the analytical results with the solution of second order finite different method. Besides, the capability of present solution in solving the industrial cases is tested. The present solution is applicable in some industrial cases such as cooling pin fins and aeronautical instruments.
... c) The convective heat transfer within the laminate due to the flowing resin from one point to another was considered negligible due to small resin velocities (low Reynolds number laminar flow). 4,33,34 d) A zero pressure boundary condition was applied at the flow boundaries by considering that the bleeders laid around the laminate were able to absorb the entire resin that comes out of laminate; ...
Article
Full-text available
A scaled, 7.5-mm thick, unidirectional glass/epoxy wind turbine spar cap cured in a vacuum-assisted oven was found to have attained non-uniform thickness along its length. Edge deformations were severe, leading to noticeable edge curvature even at the vacuum pressure. These unforeseen discrepancies could only be predicted and/or dealt beforehand through a process simulation that integrates the complete processing physics. A fully coupled numerical simulation of composites manufacturing was established and implemented for a portion of a spar cap in multiphysics finite element software. Phenomena such as resin flow-induced compaction and cure-induced deformation were captured. The simulation results indicated that even though the distorted edge of the laminate is trimmed off, there will still be some curvature left within the part. It was noted that simulating percolation flow of resin alone leads to less accurate deformation predictions. Therefore, a method to include shear flow-induced deformation of the resin-saturated fiber beds were proposed and implemented. Such a fully coupled and integrated procedure is useful for optimizing process parameters to achieve intended final part with accurate dimensions and minimal manufacturing-induced defects or deformities.
... T. Behzad and M. Sain [22] used the COMSOL multiphysics simulator to simulate curing kinetics for natural fiber reinforced composites. Temperature and cure degree profiles were studied for simple square plate and complex automotive mirror case structures. ...
Article
Full-text available
A methodology using neat resin characterization and multi‐physics process simulation was proposed to develop a resin transfer molding (RTM) process for an aircraft wing flap composite part. Initially, RTM6 resin was thermally characterized using differential scanning calorimetry and curing kinetics was modeled using Kamal and Sourour model. A multi‐physics approach was employed to simulate the RTM mold filling and curing phases. Mold filling simulations were performed to obtain an effective injection strategy for the composite part. One‐point injection port and five‐point vents were obtained as an effective injection strategy using a trial and improvement process. Curing simulations were performed on the composite part using neat resin cure kinetics and cure process windows for neat resin and composite panel were developed. Subsequently, a cure difference window was developed to investigate cure difference progression between neat resin and composite panel at the processing conditions. Finally, the kinetics of cure difference progression was modeled as a function of neat resin cure conversion to design operable cure cycles for the composite panel. The results found that the cure differences converge with the increase in applied mold temperature.
... Cette approche a été utilisée par VI Analyse multi-échelle en approche numérique et statistique de la morphologie d'un biocomposite d'arganier Silva et al. (2012) qui ont comparé les résultats de la simulation numérique avec ceux obtenus par la caractérisation expérimentale de résine époxy renforcée par les fibres de sisal et de bananier. Dans leurs travaux, Behzad and Sain (2007) présentent le point sur l'utilisation de la méthode des éléments finis pour l'estimation des propriétés effectives des biocomposites renforcés par des fibres de chanvre. Après la comparaison des résultats de la simulation avec les données expérimentales, il apparait que cette méthode est robuste et peut être utilisée pour décrire le comportement macroscopique des matériaux à renfort naturel. ...
... To optimize curing time, it is essential to know the percentage of curing progress at any point, at any moment [3]. One of the best methods to optimize the curing process is to predict temperature and degree of cure changes in different points of the polymer part by using equations and models governing heat transfer behaviour and curing kinetics [4,5]. ...
Article
The main purpose of this study is to optimize the curing time of HTPB, by analyzing the curing process in different conditions. Solving equations have been performed using OpenFOAM software and according to the finite volume method. To solve the curing equation, a new solver called CureFOAM was developed and added to the OpenFOAM. Using the experimental results available in the sources, the developed solver was validated. The maximum relative error is +5 %. After validating the CureFOAM solver, the effect of various factors affecting the curing process was simulated. Based on the results, an increase of 10 °C temperature reduces curing time to 2 days, and the use of a fan oven in the Reynolds 1500 range, reduces curing time by up to 50 percent. Also, the curing process in the mold of a rectangular cube is done faster than the cylindrical and spherical molds, in different aspect ratios.
... During the polymerization of a thermoset resin, the application of heat with light and/or a chemical catalyst causes polymer chain crosslinking, which results in the formation of a rigid polymeric material. The process of curing can be described by a non-linear transient heat transfer finite element model [73]. For illustration, a compression molding process is used as an example, in which a thermoset composite is loaded into a mold and heated via conduction for curing. ...
Article
Additive manufacturing (AM) or more commonly known as 3D-printing has gained much ground in industrial manufacturing because of its breakthrough in rapid prototyping and processes. To date, the 3D-printing market has grown significantly and is poised for growth in line with digitization of manufacturing. The main objective of this review article focuses on the viscoelastic behavior (viscous solution) of 3D printing materials at ambient conditions, which are not essentially under melt-flow or higher temperatures. The initial section reviews the basic concepts on viscosity and viscoelastic phenomenon, with emphasis on the preferred conditions a viscous material should have prior to 3D-printing. Several examples of structures formed from viscoelastic materials through 3D-printing are also detailed, as well as the various curing techniques for different printed objects or models. While there is much interest on industrial applications, the last part surveys various food formulations used for 3D-printing.
... The infusion process and cure process are independent and only the curing process is considered in this section, the reinforcement was already saturated with the resin and the resin was uniformly distributed through the fiber after completing the impregnation, which is similar to Behzad and Sain [49] of a compression mold of prepregs. There are several assumptions: the influence of resin flow on heat transfer is negligible; the geometry, the thickness, and the resin mass remain constant during the molding process; the thermo-physical properties of the resin and composite were independent of the cure rate. ...
Article
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Vacuum assisted resin infusion (VARI) has attracted more and more attentions in the aerospace field and the monitoring of the process variables has been one of the milestones for most aerospace companies. This study focuses on monitoring the flow front and curing degree of the resin in-suit using a piezoelectric (PZT) sensor network. In the resin transfer stage, the propagation characteristics of Lamb waves were extracted from different paths to characterize the resin flow front, and the quadratic regression models of three variables were established. In the resin cure stage, the leaky Lamb waves and electromechani-cal impedance based on PZT sensors were simultaneously adopted to monitor the degree of cure of the resin globally and locally, respectively. The differential scanning calorimeter analysis was carried to see the compatibility among different methods for the curing degree. Experimental results demonstrated that it was feasible to monitor the flow front and curing degree of resin in VARI process using Lamb waves and electromechanical impedance based on a multifunctional piezoelectric sensor network. K E Y W O R D S degree of cure, piezoelectric sensors, resin flow front, resin infusion
... The reason for differences in temperature profile between the numerical simulation and experimental data is due to the following assumption in modeling: (1) constant density, (2) constant thickness and (3) ignoring the effect of degree of cure on the thermal conductivity and heat capacity of the composite. As for experimental data measurement, dislocation of the thermocouple from the initial position during the compression molding process could have caused the discrepancy in temperature profile [23]. ...
Chapter
Mechanical and thermal properties of biocomposite reinforced with natural fibers have been determined traditionally from the experimental testing methods. This process is labor intensive, expensive and time-consuming. Hence, with the advancement of computational tools, modeling and analysis of the composites have become feasible. Finite element method (FEM) is a common tool used for the prediction of mechanical and thermal properties of the biocomposite. FEM-based computational analysis is relatively new and has great scope for research. Micromechanical, macromechanical and mesoscale analyses of finite-element models were used for the prediction of strength and stiffness of biocomposites. For thermal analysis, studies involve determining the thermal conductivity and analyzing the cure kinetics of the biocomposite. Hence, this chapter focuses on the various computational models used for predicting the mechanical and thermal properties of the biocomposite.
... In the past few years, many researchers have studied the effect of the volume fraction of fiber on the thermophysical and mechanical properties of composite material, like thermoplastic polyurethane reinforced with kenaf fiber [12], pineapple leaf fiber reinforced phenolformaldehyde matrix [13]. Liu et al. [8] have determined the thermal conductivity of composites reinforced with Manila hemp fiber in the matrix using numerical method and the analytical model of Hasselman-Johnson's. Behzad and Sain have determined the conductivity of composites reinforced with hemp fiber using experimental method and have developed a numerical model to determine the temperature distribution [14]. ...
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Date palm fiber bundle includes lumens in solid region, which present low thermal conductivity than that of fiber bundle. In this work, the transverse thermal conductivity of date palm fiber bundle was determined by numerical software to investigate the relation between the bundle fiber and the solid region thermophysical properties. Therefore, the results determined from the numerical investigation were compared to the analytical model to prove the numerical model developed in this study. In this context, numerical simulation of thermal conductivity was performed by the numerical finite element method by COMSOL software. To verify the developed models, the bundle fiber and solid region thermal conductivity relation were determined. Quadratic and Cubic polynomial expressions, were used to study the influence of the normalized conductivity of the bundle fiber and the solid region of the composite material and to evaluate the composites thermal conductivity. Influence of lumen on the thermal conductivity was also investigated in this work. The results indicate that the bundle fiber thermal conductivity is much less than that of the solid region thermal conductivity. This one depends on pore dimension, but not on distribution and shape of pore. The numerical results obtained from the model developed in this study are compared with analytical model to validate this model. Finally, a sensitivity analysis was conducted with the models to investigate how changes in the values of important variables, such as thermal conductivity and volume fraction of the constituent, can affect the effective thermal properties of the composite.
... The factors which affect the curing process are temperature overshoot, glass transition temperature during phase change, and resin viscosity [28,29]. This may develop the temperature and cure gradients along thick sectioned parts which results to matrix micro-cracks, residual stresses and geometrical distortions [30][31][32][33][34][35]. ...
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A review on numerical optimization of parameters involved in mould filling, and curing that affects a class of composite moulding processes, namely Liquid Composite Moulding (LCM) processes are presented. The critical issues and prevention techniques of the entire process cycle are discussed to manufacture a void-free and cost-effective composite part. The key parameters discussed under mould filling stage are preform parameters such as permeability and porosity, gate and vent location, injection pressure, and mould geometry. Whereas, the key parameters discussed under curing stage are degree of cure, mould temperature and viscosity of resin. The number of single objective and multi-objective optimization techniques have been developed to optimize the objectives like the degree of cure, temperature overshoot, process time, gate and vent location and mould fill time. The Nelder mead simplex method, simulated annealing, GA, NSGA-II, and MOOGA are the most used traditional techniques for optimizing the process as well as mould parameters. The scope of meta-heuristic or hybrid optimization techniques for constrained single and multi-objective optimization problem in the LCM process has addressed.
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A current concern of researchers is to improve the response of compressed earth blocks (CEB), mainly to water attacks by reducing the hydrophilic character of the soil matrix. this work contributes to the formulation of a new soil-based material containing argan nutshell powder (ANS), insofar as the stabilization of compacted soil by cellulosic materials allows to obtain a higher impermeability aspect. Accordingly, a regression of about 32% of the coefficient of capillary absorption has been highlighted with the addition of 2% ANS stabilizer, beyond this percentage, the decrease in absorption becomes less significant. In a vision to identify the non-linear behavior of the compressed earth blocks (CEB) reinforced by the Argan nut shells particles (ANS) influenced by many parameters like the shape, the distribution, and the quantity of the stabilizers, as well as the interactions between both phases: matrix and reinforcement. The use of numerical models seems to be indispensable. Yet, simulations of heterogeneous structures quickly become unaffordable by direct calculations on finite element software. Therefore, a homogenization of the experimental, and numerical macrostructure is performed. Thus, an overall micro-meso-macro approach to modeling the mechanical behavior of CEB/ANS biocomposites has been established. It is mainly based on the notion of the representative elementary volume with two different structures (periodic structure and structure with a poisson distribution). The numerical homogenization results were validated by the Young’s modulus values resulting from the experimental compression test and the corresponding stress–strain curves.
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Purpose The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program. Design/methodology/approach Finite element method is employed in this work. Findings The simulated results match the experimental results well, which demonstrates the finite element analysis models are reliable. Compared with the one- and two-dimensional finite element analysis, temperature and degree of cure can be calculated at any point within composite structures in the present simulation analysis. The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program. Originality/value A coupled thermokinetic simulation of the liquid composite molding process based on a three-dimensional finite element method is presented. The cure simulation of composite structures with arbitrary geometry can be investigated by the finite element program.
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In the contemporary world, natural fibers reinforced polymer composite (NFRPC) materials are of great interest owing to their eco-friendly nature, lightweight, life-cycle superiority, biodegradability, low cost, noble mechanical properties along with their developing demand on the environmental sustainability of engineering materials. NFRPCs are widely applied in various engineering sustainable applications and this research field is continuously developing. However, the researchers faced numerous challenges to the developments and applications of NFPRCs due to the inherent characteristics of natural fibers (NFs). These challenges include quality of the fiber, thermal stability, water absorption capacity, and incompatibility with the matrices. Ecological and economic concerns are animating new research in the field of NFRPCs. Furthermore, considerable research was carried out to improve the performance of NFRPCs in recent years. This review highlights some of the important breakthroughs associated with the NFRPCs in terms of sustainability, eco-friendliness, and economic perspective. It also includes hybridization of NFs with synthetic fibers which is a highly effective way of improving the mechanical properties of NFRPCs along with some chemical treatment procedures. This review also elucidates the significance of using numerical models for NFRPCs. Finally, conclusions and recommendations are drawn to assist the researchers with future research directions.
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Throughout the past, heating by electromagnetic induction has been frequently used to design speedier curing processes of adhesives. With this method, bonded components are exposed to an alternating electromagnetic field (EMF), which generates heat in EMF-sensitive adherends, like steel and aluminium, or in susceptors that are admixed to the polymers to be cured, e.g. fibres or particles. Recently, specially designed susceptors, so-called Curie particles (CP), have shown their great potential for induction curing. Heat generated in CP is capped by the materials Curie temperature (Tc), preventing the adhesive from overheating. As a result, curing proceeds way faster and independently from ambient temperatures, opening up new application fields for bonded components. Although practical applicability has already been demonstrated, CP-induced heating – and consequently curing – has proven to be very sensitive to the boundary conditions of the considered application. Therefore, induction times needed to achieve full cure must currently be determined by cumbersome and costly experimental investigations. To compensate for this disadvantage, the present study – representing the second part of a series – aimed at offering a first approach of a numerical model in which thermal and kinetic aspects of CP-induced accelerated curing were combined. For that, curing kinetics of two kinetically different 2K epoxy adhesives were linked to a transient heat flow simulation in Ansys based upon experimentally determined heat loads. Since the first part of this series concentrated on presenting all preliminary experimental work as well as analytics applied during modelling, this part focuses on the validation of the developed FEA using the exemplary application of CP-cured Glued-in Rod (GiR) specimens. In the following, various numerical parameter studies were carried out, demonstrating principal functionality of the new FEA technique and highlighting in particular its contribution for the design of more efficient and target-orientated CP-curing processes.
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The numerical modelling and simulation of empirical cure rate models presented for the non-isothermal resin transfer moulding curing process cycle. The n th order model, Kamal and Sourour's (K & S) model and their modified forms used to study the efficacy of Comsol multi-physics simulator without adding any user defined program. The appropriate value of mould temperature selected from the isothermal curing simulation of n th order model. The transient variation of degree of cure and temperature within the saturated preform has been presented. It has been observed that the models having two rate constant were not converging for the initial temperature lower than 315 K. Therefore, for the sake of uniformity we used initial temperature as 315 K for all the models and mould temperature as 380 K. Although, process cure time was less for K & S model, we observed the large temperature gradient inside the composite plate for the two rate constant models. To add on the complexity in the simulation three dimensional curved plate is simulated for 10 mm, 20 mm and 30 mm thickness. Definitely, with increase in thickness of the composite plate, the time to complete the cure reaction is increased.
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A finite element method algorithm for epoxy curing degree simulation was developed in Abaqus by integrating the discretized analytical solution of the model free kinetics into its user subroutines. This method was verified by nonisothermal and isothermal DSC experiments of an epoxy resin. By means of this method, the real manufacturing press cycle could be simulated regarding temperature distribution and curing degree with advanced curing degree‐dependent material properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46408.
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Natural fiber composites (NFCs) also termed as biocomposites offer an alternative to the existing synthetic fiber composites, due to their advantages such as abundance in nature, relatively low cost, lightweight, high strength-to-weight ratio, and most importantly their environmental aspects such as biodegradability, renewability, recyclability, and sustainability. Researchers are investigating in depth the properties of NFC to identify their reliability and accessibility for being involved in aircrafts, automotive, marine, sports' equipment, and other engineering fields. Modeling and simulation (M&S) of NFCs is a valuable method that contributes in enhancing the design and performance of natural fibers composite. Recently many researchers have applied finite element analysis to analyze NFCs' characteristics. This article aims to present a comprehensive review on recent developments in M&S of NFCs through classifying the research according to the analysis type, NFC type, model type, simulation platform and parameters, and research outcomes, shedding the light on the main applicable theories and methods in this area, aiming to let more experts know the current research status and also provide some guidance for relevant researches.
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With the increased power of optoelectronic devices, enhancing thermal conductivities of transparent materials is key to thermal dissipation. Recently, our group has experimentally demonstrated a novel composite material with both high thermal conductivity and transparency by electrospinning. In this study, a numerical model was built to explore the effective thermal conductivity of the composite with non-overlapping electrospun polymer fibers and solved by the finite element method. Effects of the side length of a representative volume element and thermal conductivity along different directions of the composite were investigated by the model by adjusting the size and angle of the representative volume element. In the meanwhile, the effects of fiber volume and fiber orientation on the effective thermal conductivity were analyzed which is realized by controlling the fiber orientation with normal distribution. The generated models consisted of randomly distributed long fibers. Moreover, the overlapping methods of fiber films were studied to optimize the thermal dissipation. The electrospun composite was applied on a light emitting diode (LED) modules in a simulation way. In those modules, simulated effective thermal conductivity of the electrospun composite was applied and the temperature reduction on phosphor of the modules have been studied. This study provides a deeper understanding of effective thermal conductivity of composite that is reinforced by continuous long fibers and a useful tool to simulate the effective thermal conductivity with desired fiber volume fraction and fiber orientation.
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In this study, an analytical solution is proposed for the problem of transient anisotropic conductive heat transfer in composite cylindrical shells. The composite shells are considered to have directional heat transfer properties, which is due to the existence of fibers which can be winded in any direction. The composite shells usually show high conductivity in the direction parallel to fiber direction and low conductivity in other two orthogonal directions. To solve the heat transfer partial differential equation, finite Fourier transform and separation of variables method are used. The present solution is used to find the temperature distribution in a composite cylindrical vessel for which the composite material is graphite/epoxy and the vessel is prone to an external heat flux and also ambient flow. The analytical solution is verified perfectly by the data obtained from a second-order finite difference solution. The solution is used to investigate the effects of values of fiber angle and material conductivity coefficients on temperature distribution of the composite cylindrical vessel. The results show the important role of fiber angle values on the temperature distribution of vessel.
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Thermal insulators have a crucial role in reducing the operational building energy. They are commonly fabricated from petrochemical materials that mostly cause negative environmental impacts. This study aims to develop banana leaves-polystyrene composites (BL-PS) as a sustainable and low-cost thermal insulator. The BL powder was mixed with PS in different weight ratios (90:10, 80:20, 70:30, and 60:40). Thermal conductivity, electrical conductivity, SEM, XRD, FTIR, TGA, and DSC were carried out on BL and BL-PS composites that were prepared with 10 wt.% of PS powder (BL-PS1) and 30 wt.% of PS powder (BL-PS3). The prepared composites show low thermal conductivity, ranged from 0.0183 to 0.03168 W/m.K. The least thermal conductivity 0.0183 W/m.K was recorded for the BL-PS1 with high crystallinity and thermal stability. The present findings may support the validity of using banana leaves composite to produce an eco-friendly inexpensive thermal insulating material.
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In this study, the equivalent heat conduction model and internal curing process optimization model of the composite material based on the cavity and twisting structure of the plant fiber were established. Also, the effects of temperature, the volume fraction of the plant fiber cavity and twist on the temperature field, curing degree, and curing deformation during the internal curing process of the jute fiber winding composite pipe were analyzed. The accuracy of process simulation was verified by the internal curing experiment based on electromagnetic heating and was combined with using the microstructure test and tensile strength test of the NOL ring. However, in the case of twisted fiber, an extreme effect on the mechanical properties of the composite was noted.
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The paper aimed at obtaining an analytical solution for the steady-state heat transfer in a hollow sphere made of functionally graded material. Two-dimensional distribution of temperature is considered to be in both radial and peripheral directions and the conductivity coefficients in both directions are a function of radius. The general boundary conditions for the interior and exterior surface of the sphere are considered so that the resulting solution can be extended to treat a wide range of functional cases. The obtained solutions are in the form of Bessel and Legendre functions. Unknown solution coefficients are achieved by applying boundary conditions and orthogonal Legendre functions' relations. The paper additionally provides results for two practical test cases to assess the robustness of the achieved solution. The influence of material constants and conductivity ratio are investigated in order to shed a light on material selection. The results confirm that the achieved general exact solution is able to adequately calculate the distribution of temperature. The validated findings of the current paper could be considered as a clue for tailoring of functionally graded spheres, like spherical vessels, based on the actual thermal boundary conditions in the manufacture process.
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Fiber reinforced materials (FRMs) can be modeled as bi-phasic materials, where different constitutive behaviors are associated with different phases. The numerical study of FRMs through a full geometrical resolution of the two phases is often computationally infeasible, and therefore most works on the subject resort to homogenization theory, and exploit strong regularity assumptions on the fibers distribution. Both approaches fall short in intermediate regimes where lack of regularity does not justify a homogenized approach, and when the fiber geometry or their numerosity render the fully resolved problem numerically intractable. In this paper, we propose a distributed Lagrange multiplier approach, where the effect of the fibers is superimposed on a background isotropic material through an independent description of the fibers. The two phases are coupled through a constraint condition, opening the way for intricate fiber-bulk couplings as well as allowing complex geometries with no alignment requirements between the discretisation of the background elastic matrix and the fibers. We analyze both a full order coupling, where the elastic matrix is coupled with fibers that have a finite thickness, as well as a reduced order model, where the position of their centerline uniquely determines the fibers. Well posedness, existence, and uniquess of solutions are shown both for the continuous models, and for the finite element discretizations. We validate our approach against the models derived by the rule of mixtures, and by the Halpin-Tsai formulation.
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Two models. E-S anti R-S unit cell models, are presented based on the thermal-electrical analogy technique. The analytical expressions for transverse thermal conductivities of unidirectional composites are derived. The dimensionless effective transverse thermal conductivities k(e) are expressed as a junction of the ratio (beta) of thermal conductivities of filler to matrix. filler volume fraction (v(f)) and the geometry ratio (rho = a/b) of the filler The optimization of transverse thermal conductivities of unidirectional composites is then analyzed under different filler volume fractions v(f), thermal conductivity ratios beta and different geometric architectures. The present analysis allows for a fairly precise evaluation of configuration performance and comparisons of different arrangements. The results show that if a composite is designed,for insulation material, we should choose rho< 1, and if a composite is designed for heat dissipating purpose, we should choose ρ > 1.
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In the present study, a new environmentally friendly thermoset resin was used to manufacture hemp fiber acrylic composites by sheet molding process for automotive applications. A finite difference method was applied to predict the cure behavior and temperature variation of hemp fiber acrylic based composites during the process. Dynamic Differential Scanning Calorimetry (DSC) was employed to determine the kinetic parameters for the curing reaction at different heating rates. It was found the experimental and predicted values are in good agreement at the lower heating rate. The thermophysical properties of the resin, fiber and composite were obtained to use in the model. The temperature profile and the degree of cure of the composite with 40% resin and 60% fiber were simulated and a comparison of numerical results with known experimental data confirms the approximate validity of the model.
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The development of temperature distribution of thick polymeric matrix laminates during an autoclave vacuum bag process was measured and compared with numerically calculated results. The finite element formulation of the transient heat transfer problem was carried out for polymeric matrix composite materials from the heat transfer differential equations including internal heat generation produced by exothermic chemical reactions. Software based on the general finite element software package was developed for numerical simulation of the entire composite process. From the experimental and numerical results, it was found that the measured temperature profiles were in good agreement with the numerical ones, and conventional cure cycles recommended by prepreg manufacturers for thin laminates should be modified to prevent temperature overshoot.
Conference Paper
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In the past few years, natural fibers are finding an increased interest in polymer matrices. The natural fibers serve as reinforcement by enhancing the strength and stiffness to the resulting composite structure. In this study, a novel processing technique has been developed for water based thermoset polymers to prepare resin-impregnated mats, which can be used for sheet molding process to manufacture complex automotive semi-structural and structural parts. In order to optimize the curing conditions the mechanical properties of composites at different curing temperature and the crosslink density of the composites cured at different times were evaluated. The optimum curing cycle was obtained at 180 ºC for 10 min. Composites with one and two layers of impregnated mat with 40 % resin and 60 % fiber were manufactured and their performance were evaluated. The mechanical properties of the cured pure resin and hemp fiber acrylic based composites with two different fiber lengths were measured and the effect of fiber content and fiber length were investigated. The flexural strength was found to be around 94 MPa and the flexural modulus was 14 GPa for the composite.
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Biocomposites were made by a novel high volume processing technique named biocomposite sheet molding compound panel (BCSMCP) manufacturing process. This process design was inspired by the commercial glass fiber–polyester resin composite fabrication method called sheet molding compounding (SMC). This process yields continuous production of biocomposites on a large scale, and thus can be easily adopted in industries. A unique fiber dispersion method, which enabled uniform distribution of natural fibers, was used in this process. Consistency of the process was tested by evaluating the repeatability of the resultant materials mechanical properties. The low cost biocomposites produced as a result of the processing will be used for various panel applications such as housing and transportation. The molded samples were tested for various mechanical and thermal properties, in accordance with ASTM procedures. The biocomposites were made with various natural fibers including, big blue stem grass, jute, and industrial hemp. By combining different natural fibers in varying mass fractions, hybrid biocomposites were made using this process. Grass fiber reinforced polyester biocomposites processed by the SMC line showed very promising results.
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 In the following we present a computer simulation tool coupled with a numerical optimisation method that have been developed for use in the optimal design of the cure cycle of the production of thermoset- matrix composite parts. Their use permits the fast and straightforward optimal design of the cure cycles and leads to improved quality, reduced production times and reduced scrap. For the simulation of the cure cycle a one-dimensional non-linear transient model has been developed and coupled with the Evolution Strategy, of the Genetic Algorithms family, for the optimal design of the cure cycle of thick composite parts taking into account various realistic restrictions and targets of the production. The effectiveness and the usefulness of the proposed approach are demonstrated for several target performances together with a comparison between optimisation methods for the optimal tuning of the cure cycle.  In dieser Arbeit wird ein neu entwickeltes Computersimulations-werkzeug vorgestellt, das eine optimierte Auslegung des Herstellungsprozesses von Thermo-Set Verbundwerkstoffteilen ermöglicht. Sein Einsatz führt direkt zu einer Qualitätsverbesserung, einer Reduzierung der Fertigungszeiten und der Reduzierung des Ausschussess. Unter Berücksichtigung von verschiedenen realistischen Beschränkungen der Produktion wurde ein eindimensionales, nichtlineares Modell für die Simulation des instationären „Curing“-Prozesses entwickelt, das mit der Evolutionsstrategie der Familie der genetischen Algorithmen verbunden wurde. Die Wirksamkeit und Nützlichkeit des vorgeschlagenen Ansatzes wird anhand von unterschiedlichen Fallbeispielen dargestellt.
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Natural fibers are emerging as low cost, lightweight and apparently environmentally superior alternatives to glass fibers in composites. We review select comparative life cycle assessment studies of natural fiber and glass fiber composites, and identify key drivers of their relative environmental performance. Natural fiber composites are likely to be environmentally superior to glass fiber composites in most cases for the following reasons: (1) natural fiber production has lower environmental impacts compared to glass fiber production; (2) natural fiber composites have higher fiber content for equivalent performance, reducing more polluting base polymer content; (3) the light-weight natural fiber composites improve fuel efficiency and reduce emissions in the use phase of the component, especially in auto applications; and (4) end of life incineration of natural fibers results in recovered energy and carbon credits.
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In this paper, a finite element formulation was introduced for the three-dimensional cure simulation of composite structures. Based on the formulation, a three-dimensional finite element code was developed. Numerical examples found in the literatures were solved for code verification. Results from the present analyses agreed well with the measured cure-induced temperatures. Unlike in one or two dimensional analysis, temperature and degree of cure were able to be calculated at any point within composite structures in the present analysis. The finite element program can be used for the cure simulation of composite structures with arbitrary geometry under non-uniform autoclave temperature distribution.
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Plastic fiber composites, consisting of polypropylene (PP) or polyethylene (PE), and pinewood, big blue stem (BBS), soybean hulls, or distillers dried grain and solubles (DDGS), were prepared by extrusion. Young's modulus, tensile and flexural strengths, melt flow, shrinkage, and impact energy, with respect to the type, amount, and size of fiber on composites, were evaluated. Young's moduli under tensile load of wood, BBS, and soybean-hull fiber composites, compared with those of pure plastic controls, were either comparable or higher. Tensile strength significantly decreased for all the PP/fiber composites when compared with that of the control. Strength of BBS fiber composites was higher than or comparable to that of wood. When natural fibers were added there was a significant decrease in the melt flow index for both plastic/fiber composites. There was no significant difference in the shrinkage of all fiber/plastic composites compared to that of controls. BBS/PE plastic composites resulted in higher notched impact strength than that of wood or soybean-hull fiber composites. There was significant reduction in the unnotched impact strength compared to that of controls. BBS has the potential to be used as reinforcing materials for low-cost composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2484–2493, 2004
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Duringthe curingprocess of thick glass/epoxy composite laminates, substantial amounts of temperature lagand overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites, which require a long time for full and uniform consolidation. In this work, the temperature profiles of a 20mm thick unidirectional glass/epoxy laminate duringan autoclave vacuum bag process were measured and compared with the numerically calculated results. For the calculation of distributions of the temperature, degree of cure, resin pressure, exothermic heat and required time for full consolidation by three-dimensional finite element analyses, the effects of convective heat transfer coefficient and geometry of mold and bagging assembly on the temperature profiles were taken into consideration. Based on the numerical results, an optimized cure cycle with the coolingand reheatingsteps was developed by minimizingthe objective function to reduce the temperature overshoot in the composite. From the experimental and numerical results, it was found that the measured temperature profiles were in good agreement with the numerical ones, and conventional cure cycles recommended by prepregmanufacturers for thin laminates should be modified to prevent temperature overshoot and to obtain full consolidation.
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In this work hemp/kenaf fiber-unsaturated polyester composites were manufactured using a resin transfer molding (RTM) process. The fiber mats, with a moisture content of 4.3% at 50% relative humidity, were dried in the mold under vacuum to reach a moisture content around 1–2%. RTM composites with various fiber contents, up to 20.6% by volume, were manufactured. The wetting of the fibers was very good. The resin injection time was observed to increase dramatically at high fiber contents due to the low permeability of the mat. Keeping a constant mold temperature is the key to obtain fast and homogeneous curing of the part. The cure of the resin in the mold was simulated. It was shown to be in good agreement with experimental results obtained by thermal measurements at different positions in the cavity. The performance of these samples was evaluated by measuring tensile strength and flexural strength.
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This paper presents a procedure for using a general-purpose finite-element (FE) package for cure modeling. The package is used to carry out transient heat-transfer analysis and two user programs are developed to simulate resin-cure kinetics by using nodal control volumes based on the FE mesh. The theoretical background and numerical implementation of the procedure are described, and stability with respect to the FE mesh density and the length of the time step employed is investigated. Application of the procedure is demonstrated by modeling the cure of a thick prepreg laminate, a honeycomb sandwich panel and an I-beam. Predicted temperature profiles in the thick laminate are in excellent agreement with available experimental data.
Article
The cure kinetics of an unsaturated polyester resin were studied by differential scanning calorimetry (DSC), and different dynamic and isothermal procedures were compared. It was established that the isothermal kinetic analysis through the isoconversional adjustment lnt = A + E/RT is the method that offers the most accurate results for unsaturated polyester resin cure kinetics. From this comparative study it was noted that the activation energy not only varies according to the degree of conversion but also according to the method used to evaluate the kinetic parameters. Furthermore, it was shown that the activation energy cannot be separated from the other adjustment parameters, so the different kinetic procedures used are not generally comparable. Different methods of evaluating the degrees of conversion α and the reaction rates dα/dt according to the experimental reaction heat were also studied. It was found that the method used has a strong influence on the values of α and dα/dt, but only a slight one on the kinetic parameters.
Book
The contents of this book are: Theory of Heat Conduction and Heat-conduction Equations; Thermal Conductivity; Steady Heat Conduction; Unsteady Heat Conduction; Forced Convection in Laminar Flow; Forced Convection in Turbulent Flow; Dimensional Analysis; Forced Convection in Separated Flow; Natural Convection; Radiation of Strongly Absorbing Media; and Radiation of Weakly Absorbing Media.
Article
A coupled thermo-kinetic simulation of the liquid composite molding process based on a three-dimensional Galerkin finite element method is presented. The thermal equilibrium and chemical kinetics during the curing phase of Resin Transfer Molding process are obtained subject to mold temperature history and corresponding manufacturing process plans. The temperature and degree of cure fields, as well as their respective gradients are obtained during the curing process. The finite element implementation is geared toward solving large mesh problems in reasonable computational time by using banded in-core storage and storage of equations at the boundary nodes in a sparse matrix. Two numerical solutions are presented to illustrate the results obtained using this methodology. The obtained numerical solutions are compared with experimental data available in the literature.
Article
The thermal conductivity of hemp fiber reinforced polymer composites were studied from the steady state temperature drop across samples exposed to a known heat flux. The transverse and in-plane thermal conductivities for oriented and randomly oriented composites for different volume fractions of fiber were investigated. Experimental results showed that the orientation of fibers has a significant effect on the thermal conductivity of composites. To validate the experimental results, the heating tests for the thermal conductivity measurements were simulated by a finite element model using the thermal conductivity values obtained from the experiments. Predicted temperatures show close agreement with measured temperatures. Moreover, the experimental results of thermal conductivities of composites at different directions were compared with two theoretical models and illustrated good agreement between the obtained results and models. POLYM. ENG. SCI. 47:977–983, 2007. © 2007 Society of Plastics Engineers
Article
Sustainability, industrial ecology, eco-efficiency, and green chemistry are guiding the development of the next generation of materials, products, and processes. Biodegradable plastics and bio-based polymer products based on annually renewable agricultural and biomass feedstock can form the basis for a portfolio of sustainable, eco-efficient products that can compete and capture markets currently dominated by products based exclusively on petroleum feedstock. Natural/Biofiber composites (Bio-Composites) are emerging as a viable alternative to glass fiber reinforced composites especially in automotive and building product applications. The combination of biofibers such as kenaf, hemp, flax, jute, henequen, pineapple leaf fiber, and sisal with polymer matrices from both nonrenewable and renewable resources to produce composite materials that are competitive with synthetic composites requires special attention, i.e., biofiber–matrix interface and novel processing. Natural fiber–reinforced polypropylene composites have attained commercial attraction in automotive industries. Natural fiber—polypropylene or natural fiber—polyester composites are not sufficiently eco-friendly because of the petroleum-based source and the nonbiodegradable nature of the polymer matrix. Using natural fibers with polymers based on renewable resources will allow many environmental issues to be solved. By embedding biofibers with renewable resource–based biopolymers such as cellulosic plastics; polylactides; starch plastics; polyhydroxyalkanoates (bacterial polyesters); and soy-based plastics, the so-called green bio-composites are continuously being developed.
Article
The mechanical behaviour high density polyethylene (HDPE) reinforced with continuous henequen fibres (Agave fourcroydes) was studied. Fibre-matrix adhesion was promoted by fibre surface modifications using an alkaline treatment and a matrix preimpregnation together with a silane coupling agent. The use of the silane coupling agent to promote a chemical interaction, improved the degree of fibre-matrix adhesion. However, it was found that the resulting strength and stiffness of the composite depended on the amount of silane deposited on the fibre. A maximum value for the tensile strength was obtained for a certain silane concentration but when using higher concentrations, the tensile strength did not increase. Using the silane concentration that resulted in higher tensile strength values, the flexural and shear properties were also studied. The elastic modulus of the composite did not improve with the fibre surface modification. The elastic modulus, in the longitudinal fibre direction obtained from the tensile and flexural measurements was compared with values calculated using the rule of mixtures. It was observed that the increase in stiffness from the use of henequen fibres was approximately 80% of the calculated values. The increase in the mechanical properties ranged between 3 and 43%, for the longitudinal tensile and flexural properties, whereas in the transverse direction to the fibre, the increase was greater than 50% with respect to the properties of the composite made with untreated fibre composite. In the case of the shear strength, the increase was of the order of 50%. From the failure surfaces it was observed that with increasing fibre-matrix interaction the failure mode changed from interfacial failure to matrix failure.
Article
An analysis of the cure kinetics of epoxy resin with an acrylic copolymer (acrylic acid-butyl acrylate-methylmethacrylate) using a dimethylbenzolamine (DMBA) catalyst is presented. The kinetic studies were carried out with a dynamic scanning calorimeter in both dynamic (Barret, Freeman-Carroll and Kissinger Methods) and isothermal modes of operation. The effects of heating rates and catalyst concentration on the activation energy and reaction order were investigated. The activation energy found in the dynamic experiments was on the order of 22 kcalmol. In the same set of experiments, the frequency factor of the effective rate constant varied from 4.9 × 108 to 3.6 × 109 sec−1, and the order of reaction increased from 1.2 to 1.4 as a function of the catalyst concentration. On the other hand, the isothermal experiments yielded slightly different results: a frequency factor on the order of 8.9 × 108 sec−1, a reaction order of approximately 1.1, and an activation energy of 17.9 kcal mol−1.
Article
Chemical treatment of natural reinforcements can enhance their adhesion to polymer matrices. This work reports the effects of different treatments on the fibre–matrix compatibility in terms of surface energy and mechanical properties of composites. The composites were compounded with two kinds of flax fibres (natural flax and flax pulp) and polypropylene. The applied treatments were maleic anhydride (MA), maleic anhydride-polypropylene copolymer (MAPP) and vinyl trimethoxy silane (VTMO). The treatment effects on the fibres have been characterised by Infrared Spectroscopy. Two techniques have been used to determine the surface energy values: the Dynamic Contact Angle method for the long flax fibres and the Capillary Rise method for the irregular pulps. The use of different methods involves a small discordance in the wettability values. Nevertheless, the three treatments reduce the polar component of the surface energy of the fibre. Composites containing MAPP-treated did the highest mechanical properties, whilst the MA and VTMO-treated fibre gave similar values to that for the untreated ones.
Article
This paper describes the development and validation of a numerical procedure for the simulation of temperature and cure profiles for the pultrusion process. The governing equations for heat transfer and the resin cure reaction during pultrusion are presented. A new finite-element/finite-difference/control-volume procedure is developed to solve the governing equations. The accuracy and other numerical behavior of the procedure are investigated by a number of numerical simulations. It is shown that the procedure is numerically stable and predicts the temperature and cure profiles which are in good agreement with those published by other researchers.
Article
In this paper, a finite element formulation for three-dimensional cure simulation of composite structures is introduced and a three-dimensional finite element code is developed based on the formulation. Results from the present cure simulations agreed well with the measured cure-induced temperatures and the numerical results from one- or two-dimensional simulations. Unlike in the one- and two-dimensional simulations, temperature and degree of cure can be calculated at any point within composite structures in the present analysis. The finite element program can be used for cure simulation of composite structures with arbitrary geometry under non-uniform autoclave temperature distribution.
Article
This paper deals with the modelling and simulation of resin flow, heat transfer and the curing of multilayer thermoset composite laminates during processing in an autoclave. Darcy's Law and Stokes’ slow-flow equations are used for the flow model and, for approximately isothermal flows, a similarity solution is developed. This permits the decoupling of the velocity and thermal fields. A two-dimensional convection–diffusion heat equation with an internal heat generation term is then solved numerically, together with the equation for the rate of cure, using a finite difference scheme on a moving grid. The simulations are performed with varying composite thicknesses, and a comparison of numerical results with known experimental data confirms the approximate validity of the model.
Article
Natural rubber is reinforced with untreated sisal and oil palm fibers chopped to different fiber lengths. The effects of concentration and modification of fiber surface in sisal/oil palm hybrid fiber reinforced rubber composites have been studied. Increasing the concentration of fibers resulted in reduction of tensile strength and tear strength, but increased modulus of the composites. Composites were prepared using fibers treated with varying concentrations of sodium hydroxide solution and for different time intervals. The vulcanisation parameters, processability characteristics, and stress–strain properties of these composites were analysed. The rubber/fiber interface was improved by the addition of a resorcinol-hexamethylene tetramine bonding system. The reinforcing property of the alkali treated fiber was compared with that of untreated fiber. The extent of fiber alignment and strength of fiber-rubber interface adhesion were analysed from the anisotropic swelling measurements.
Curing kinetics of an acrylic/epoxy resin system using dynamic scanning calorimetry Cure simulation of hemp fiber acrylic based composites during sheet molding process
  • F Chu
  • T Mckenna
  • S Lu
  • T Behzad
  • Sain
Chu F, Mckenna T, Lu S. Curing kinetics of an acrylic/epoxy resin system using dynamic scanning calorimetry. Eur Polym J 1997;33(6):837–40. [22] Behzad T, Sain M. Cure simulation of hemp fiber acrylic based composites during sheet molding process. Polym Polym Compos 2005;13(3):235–43.
Degree of cure distributions at different curing times in various slides of the structure: (a) curing time = 50 s and (b) curing time = 500 s (units of axis are in meters)
  • Fig
Fig. 10. Degree of cure distributions at different curing times in various slides of the structure: (a) curing time = 50 s and (b) curing time = 500 s (units of axis are in meters).
Analysis of heat and mass transfer. Mcgra- Hill: Hemisphere Publishing Corporation
  • Erg Eckert
  • Rm Drake
[19] Eckert ERG, Drake RM. Analysis of heat and mass transfer. Mcgra- Hill: Hemisphere Publishing Corporation; 1972. Part A Heat conduction.
Mcgra-Hill: Hemisphere Publishing Corporation
  • Erg Eckert
  • R M Drake
Eckert ERG, Drake RM. Analysis of heat and mass transfer. Mcgra-Hill: Hemisphere Publishing Corporation; 1972. Part A Heat conduction.