Balanced Plain Weave Research Articles

Parametric characterization of a mesomechanic kinematic in plain and twill weave 2/2 reinforced composites by FE-calculations

Purpose: A parametric characterization of a mesomechanic kinematic caused by ondulation in fabric reinforced composites is investigated by numerical investigations. Design/methodology/approach: Due to the definition of plain representative sequences of balanced plain-weave and twill-weave 2/2 fabric reinforced single layers based on sines the variable geometric parameters are the amplitude and the length of the ondulation. Findings: The mesomechanic kinematic can be observed in the FE analyses for both kinds of fabric constructions. Research limitations/implications: The FE analyses consider elasticity and contraction due to Poisson effects, respectively, of the model under selected longitudinal strains. Practical implications: The results are evaluated at relevant positions on the centre-line of the ondulated warp-yarn of the plain representative model. A direct and linear coupling in case of the transversal kinematic behaviour, and thereby a corresponding definite reduction of the evaluated longitudinal strains in terms of the difference of the applied and determined longitudinal strains is identified. Originality/value: Both characteristic purely kinematic reactions due to geometric constraints directly depend on the introduced degree of ondulation. This non-dimensional parameter relates amplitude and length of one complete ondulation, and thus represents the intensity of the ondulation of the respective fabric construction.

An anisotropic hyperelastic constitutive model for plain weave fabric considering biaxial tension coupling

A nonlinear anisotropic hyperelastic constitutive model is developed for plain weave fabrics by considering biaxial tensile coupling. The strain energy function is decomposed into two parts to represent tensile energy, including the biaxial tensile coupling effect from fiber elongation and shearing energy from relative rotation between warp and weft yarns. A simple and efficient material parameter identification method is proposed. The model is exemplified on a balanced plain weave glass fabric. Experimental data from the literature are used to identify material parameters in the constitutive model. Model validation is implemented by comparing numerical results with various experimental data, including biaxial tension tests under different stretch ratios and the picture frame shearing test. The developed constitutive model is applied to numerical simulation of a double-dome stamping of the plain weave fabric. The influences of binder force and initial fiber yarn orientation on forming are investigated. Numerical results demonstrated that the biaxial tensile coupling effect could not be neglected in forming simulation. The developed constitutive model is suitable to characterize the nonlinear behavior of plain weave fabrics under large deformation.

Modelling, simulation and experimental validation of bend tests on GFRP laminate beam and plate specimens

The study concerns glass-polyester laminates, i.e. polyester resin reinforced with E-glass balanced plain weave fabric and/or E-glass mat. Experimental 3-point bend tests were carried out on homogeneous laminate beams reinforced with glass fabric or glass mat and on mixed laminate beams and plates reinforced with a glass fabric/glass mat ply sequence. In order to select the adequate failure criteria, bend tests on homogeneous laminate beams were modelled numerically and simulated using MSC.Marc finite element code. In relation to laminae reinforced with glass fabric the Hashin Fabric failure criterion was selected, and in reference to laminae reinforced each with glass mat the Max Strain failure criterion was selected. The adequacy of the selected failure criteria was validated experimentally by bend tests on mixed laminate beams and plates. Good qualitative and quantitative agreement of the simulated pressure force vs. deflection charts with those of the experimental tests was obtained.

A general micromechanical model to predict elastic and strength properties of balanced plain weave fabric composites

In the present research, a micromechanical-analytical model was developed to predict the elastic properties and strength of balanced plain weave fabric composites. In this way, a new homogenization method has been developed by using a laminate analogy method for the balanced plain weave fabric composites. The proposed homogenization method is a multi-scale homogenization procedure. This model divides the representative volume element to several sub-elements, in a way that the combination of the sub-elements can be considered as a laminated composite. To determine the mechanical properties of laminates, instead of using an iso-strain assumption, the assumptions of constant in-plane strains and constant out-of-plane stress have been considered. The applied assumptions improve the accuracy of prediction of mechanical properties of balanced plain weave fabrics composites, especially the out-of-plane elastic properties. Also, the stress analysis for prediction of strain–stress behavior and strength has been implemented in a similar manner. In addition, the nonlinear mechanical behavior of balanced plain weave composite is studied by considering the inelastic mechanical behavior of its polymeric matrix. To assess the accuracy of the present model, the results were compared with available results in the literature. The results, including of engineering constants (elastic modulus and Poisson’s ratio) and stress–strain behavior show the accuracy of the present model.

Uniaxial tensile and impact investigation of carbon-fabric/polycarbonate composites with different weave tow widths

Flexible thermoplastic composites hold great potential in the automobile industry due to their high specific strength and modulus, good recyclability and high productivity. In this work, a novel single-layered ultra-thin (≤0.3mm thick) carbon-fabric/polycarbonate composite was laminated with two thin polycarbonate (PC) films as the matrix and a woven carbon fabric as reinforcement, adopting a balanced plain weave method combined with a hot-press technique. For the carbon fiber (CF) tow, thousands of filaments are packed with high density in a tape shape so that the permeation resistance of the matrix during hot-press increases, especially for a low molding temperature, inducing poor CF-PC bonding. To address this matter, raw CF tows were spread into a fabric prior to weaving. Three spread CF tows, 8, 14, and 20mm in width, were used to investigate the effect of the tow width on the tensile strength and impact properties of the as-prepared composites. The experimental results showed that the 20mm wide tow performed better with respect to normalized tensile strength, shear strength, peak force and penetration energy than the 8 and 14mm tows, which can be attributed to its enhanced impregnation between the CF and PC matrix.

Flexural and low velocity impact characterization of thermoplastic composites based on PEN and high performance woven fabrics

Poly(Ethylene 2,6‐Naphthalate)—PEN has been used as matrix for laminates with the aim to develop woven fiber reinforced composites with a service temperature as high as 100°C. Three different classes of fibers have been considered as reinforcement in woven fabric form: carbon, polymers (Twaron and Vectran) and mineral (basalt). Composites were manufactured by using the film stacking technique, alternating layers of balanced plain weave fabrics (0/90) and films of amorphous PEN. The manufacturing process was optimized to obtain a good impregnation of fibers and very low void content. Static flexural tests, dynamic mechanical analysis and low velocity impacts were used to characterize the mechanical behavior of the composites. The flexural modulus and strength of laminates resulted to be very high, in particular for the PEN/Carbon and PEN/Basalt systems. The storage modulus from the dynamic mechanical analysis indicated that 100°C is a suitable service temperature for all configurations. The impact resistance of the composites showed a different trend with respect to static tests, since PEN/Basalt and PEN/Aramid exhibited the best performances. These results prove that PEN is a viable option for the production of structural composites as replacement of thermosetting matrices due to its high performance/cost ratio, in particular when combined with basalt fibers. POLYM. COMPOS., 39:2942–2951, 2018. © 2017 Society of Plastics Engineers

Effect of temperature on static and low velocity impact properties of thermoplastic composites

Abstract In this work, thermoplastic composites based on poly(ethylene 2,6-naphthalate) (PEN) have been investigated with the aim to elucidate the effect of temperature on static and impact properties. The matrix was reinforced with four different high performing woven fabrics based on carbon, Twaron, Vectran, basalt fibres. Composites were manufactured by using the film stacking technique, alternating layers of balanced plain weave fabrics (0/90) and films of amorphous PEN, keeping the fibre volume fraction around 40%. The compression moulding process was optimized to obtain optimal fabric impregnation and to keep the void content lower than 1%. The structural response was evaluated at 20 °C, 60 °C and 100 °C by means of static flexural and low velocity impact tests. Dynamic mechanical scans (DMA) were also performed to evaluate the stiffness of the laminates at temperatures ranging from – 80 °C to 230 °C. The flexural modulus and strength of laminates resulted to be very high in proportion with the fibre stiffness. The flexural behaviour was affected by the temperature but a limited reduction of the stiffness (lower than 20%) was exhibited by all but PEN/Vectran up to temperatures of 100 °C. PEN/carbon resulted the best performing system at each testing temperature (flexural modulus equal to 38.8 GPa, flexural strength equal to 714 MPa at 20 °C). Results from DMA tests demonstrated a satisfactory agreement with static tests (differences within ±13%, except that for PEN/Vectran). The impact resistance of the composites was found to depend on the fibre type, temperature and interface strength. PEN/basalt resulted the best performing composite followed by PEN/Twaron (perforation energy at 20 °C: 44.3 J and 38.2 J, respectively). The PEN/carbon laminate exhibited the lowest impact performance but, unlike PEN/basalt and PEN/Vectran, the impact resistance improved with the increasing temperature.

Mechanically coupled laminates with balanced plain weave

Abstract Definitive listings of laminate stacking sequences are derived for balanced plain weave laminated materials, assuming each layer is composed of the same material with constant thickness throughout and that standard ply angle orientations 0, 90, and ±45° are adopted; consistent with industrial design practice. A single layer of balanced plain weave material is shown to be immune to thermal distortion following a standard high temperature manufacturing process, which implies that all laminates constructed of this material possess what is commonly referred to as the hygro-thermally curvature-stable or warp-free condition, irrespective of the individual ply orientations used or the laminate stacking sequence definition. A single uncoupled parent laminate class is shown to contain sub-groups with extensionally isotropic and fully isotropic properties that are invariant with off-axis orientation of the principal material axes with respect to the system or structural axes. By contrast a single mechanically coupled parent laminate class is shown to give rise to seven unique forms of coupled laminate through judicious off-axis orientation. Invariant off-axis properties are also identified in coupled laminate designs. Finally, example calculations, abridged stacking sequence listings and design data are presented.

Characterization of the tool/fabric and fabric/fabric friction for woven-fabric composites during the thermostamping process

The dynamic coefficients of friction for Twintex® commingled glass-polypropylene balanced plain-weave and unbalanced twill-weave fabrics at the tool/fabric and fabric/fabric interfaces during the composite thermostamping process are characterized. The effects of fabric velocity and pressure on the coefficients of friction under conditions similar to those during the thermostamping process are studied. A phenomenological friction model accounting for pressure and velocity dependence is developed based on the experimental results and implemented into the commercial finite element codes ABAQUS/Explicit and LS-DYNA via user-defined subroutines. The mechanical behavior of the fabric is modeled using a mesoscopic approach. The friction subroutines are validated with a finite element model of the experimental friction test. The forming of a hemispherical dome is simulated using ABAQUS and LS-DYNA. Punch forces and yarn stresses are compared between variable friction and constant friction models, and the simulation results justify the necessity for a variable friction model to accurately predict part quality.

3D Geometrical Model of Plain Weave Fabrics for Finite Element Analysis

Woven unit-cell geometry functions are presented for a balanced plain weave fabric. Based on the functions, a 3D geometrical model applying to a meshing preprocessor for 3D finite element is proposed. The geometry model takes into account the existence of the space between tows, the undulation of the tow, and the actual tow cross-section shape. The internal geometry of model is from micrographs of sectioned laminates, which is helpful to define the accurate and actual 3D geometrical model. The section shape of the yarn remains unchanged along the trajectory. This model can be easily identified using three parameters measured on a real fabric. An accurate hexahedral mesh developed using these geometry model is presented. This is an important point for 3D finite element simulation of fabric model, which is a powerful method to investigate the mechanical behavior and also the composites made from it.

Textile composite double dome stamping simulation using a non-orthogonal constitutive model

Stamping is one of the most effective ways to form textile composites in industry for providing high-strength, low-weight and cost-effective products. This paper presents a fully continuum mechanics-based approach for stamping simulation of textile fiber reinforced composites by using finite element (FE) method. A previously developed non-orthogonal constitutive model is used to represent the anisotropic mechanical behavior of textile composites under large deformation during stamping. Simulation are performed on a balanced plain weave composite with 0°/90° and ±45° as initial yarn orientation over a benchmark double dome device. Simulation results show good agreement with experimental output in terms of a number of parameters selected for comparison. The effects of meshing and shear moduli obtained from bias extension test and picture frame test on forming simulation results are also investigated.

A Simple Anisotropic Fiber Reinforced Hyperelastic Constitutive Model for Woven Composite Fabrics

Based on fiber reinforced continuum mechanics theory, a simple hyperelastic constitutive model is developed to characterize the anisotropic nonlinear material behaviour of woven composite fabrics under large deformation during forming. The strain energy function for the hyperelastic model is additively decomposed into two parts nominally representing the tensile energy from weft and warp yarn fiber stretches and shearing energy from fiber-fiber interaction between weft and warp yarns, respectively. The proposed material characterization approach is demonstrated on a balanced plain weave composite fabric. The equivalent material parameters in the hyperelastic constitutive model are obtained by matching experimental load-displacement data of uni-axial tensile and picture frame tests on the woven composite fabric. The development of this anisotropic fiber reinforced hyperelastic model is critical to the numerical simulation and optimization of woven composites forming.

Delamination Tests of DCB Specimens Composed of Woven Composites

In this investigation, quasi-static fracture tests double cantilever beam (DCB) woven composite specimens containing a straight through delamination are presented. The specimen is shown in Fig. 1. The fibers are carbon 300T which are transversely isotropic. The epoxy matrix is 913 and is isotropic. Each ply is a balanced plain weave of carbon fiber yarn in an epoxy matrix. The plies are laid up so that they alternate between a 0°/90° and a +45°/ − 45° weave. There are 15 plies with the delamination located between the seventh and eighth plies. Thus the interface is between a 0°/90° weave and a +45°/ − 45° weave. Each of these plies is anisotropic. Mechanical properties were calculated by means of the High Fidelity Generalized Method of Cells (HFGMC) [1]. The specimens are based on the ASTM Standard D5528-01 [2] which is used for testing unidirectional composites. In order to obtain a relation between the interface energy release rate Gi, the mode mixity phase angles, the applied load and crack length, finite element analyses were carried out. The stress intensity factors were determined by means of an interaction energy integral. To this end, the Stroh formalism [3] was used to determine the first term of the asymptotic expressions for the stress and displacement fields in the neighborhood of the delamination front. Similar methods have been used for straight through delaminations in cross-plies [4, 5]. The experimental set-up consists of an Instron loading machine (no. 8872) with a load cell of maximum load 250 N. This small load cell is required since the maximum load at fracture is approximately 60 N. The Instron measures the load as a function of time.

Thermal–mechanical cell model for unbalanced plain weave woven fabric composites

A high fidelity assessment of accumulative damage of woven fabric composite structures subjected to aggressive loadings is strongly reliant on the accurate characterization of the inherent multiscale microstructures and the underlying deformation phenomena. The stress and strain fields predicted at a global structural level are unable to determine the damage and failure mechanisms at the constituent level and the resulting stiffness degradation. To establish a mapping relation between the global and constituent response parameters, a new four-cell micromechanics model is developed for an unbalanced weave subjected to a thermal–mechanical loading. The developed four-cell micromechanics model not only bridges the material response from one length scale to another but also quantifies the composite thermal–mechanical properties at a given state of constituent damage. The thermal–mechanical mapping relations at different microstructural levels are derived based on the multicell homogenization, intercell compatibility conditions, and energy methods. Because of the high computational efficiency of the developed thermal–mechanical micromechanics model, it can be linked with a finite-element-based dynamic progressive failure model, where the response parameters at different microstructural levels can be extracted for each Gaussian point and at each time step. The accuracy and the dual function of the developed micromechanics model are demonstrated with its application to a balanced plain weave, an unbalanced plain weave, and failure mode simulation of a tensile coupon test.

Prediction of Thermal Conductivities of Fibre Reinforced Composites using a Thermal-Electrical Analogy

An approach for predicting the effective thermal conductivities of fibre reinforced composites has been developed, based on a thermal-electrical analogy. In the voxelization method, the unit cell of the laminate composites is divided into a number of volume elements, and the material properties considering the local variations of fibre orientation have been given to each element. By constructing a series-parallel thermal resistance network, the thermal conductivities of a fibre reinforced composite in both in-plane and out-of-plane directions have been predicted. The reported thermal conductivities of a graphite/epoxy composite of a balanced plain weave laminate were used for the comparison with the predicted values of the model, and good agreement was found.

A continuum mechanics-based non-orthogonal constitutive model for woven composite fabrics

Abstract A non-orthogonal constitutive model is developed to characterize the anisotropic material behavior of woven composite fabrics under large deformation. A convected coordinate system, whose in-plane axes are coincident with the weft and warp yarns of woven fabrics, are embedded in the shell elements. Contravariant stress components and covariant strain components in a constitutive relation are introduced into the convected coordinate system. The transformations between the contravariant/covariant components and the Cartesian components of the stress and strain tensors provide an approach for deriving the global non-orthogonal constitutive relations for woven composite fabrics. By taking advantage of the tensile–shear decoupling in the constitutive equation under the convected coordinate system, the material characterization of woven fabrics is simplified. As an essential part for these transformations, a fiber orientation model is developed, by using some fundamental continuum mechanics concepts, to trace the yarn reorientation of woven fabrics during deformation. The proposed material characterization approach is demonstrated on a balanced plain weave composite fabric. The equivalent material properties are obtained by matching with experimental data of tensile and bias extension tests on the woven composite fabric. Model validation is provided by comparing numerical results with experimental data of bias extension test and shear test. The development of this non-orthogonal model is critical to the ultimate goal, i.e. using numerical simulations to optimize the forming of woven composite fabric sheets.

Modeling of Friction and Shear in Thermostamping of Composites - Part II

Fabric shear is being considered as the main deformation mode in the thermostamping process of composites. To predict the change of the shear properties of composites during the process, a combined friction and compaction model is developed based on the equilibrium equations of the unit cell of a balanced plainweave glass/polypropylene woven fabric. The advantage of this approach over the earlier models is that it does not require curve fitting of the fabric-level experimental data. In addition, it considers both lateral compaction and friction. Picture frame experimental results are presented to validate this model. A very close correlation is observed between the model predictions and the experimental results. The material stress-strain relationship needed for input to stamping simulations is then calculated using the results of the picture frame model.

Homogenization of balanced plain weave composites with imperfect microstructure: Part I––Theoretical formulation

A mathematically sound computational framework is presented for the determination of a representative volume element (RVE) of plain weave fabric composites with reinforcement imperfections. Although treated as periodic two-phase composites the imperfect geometry of such material systems often precludes a straightforward representation of the RVE in terms of a simple periodic unit cell (PUC). To circumvent various limitations of simple unit cells when applied to real material systems the present contribution suggests a rigorous theoretical approach for the derivation of a reliable PUC exploiting the knowledge of the real geometry of a composite supplied by the manufacturer. It is expected that sufficient geometrical information about the real microstucture can be obtained from digitized micrographs of plain weave cross-sections that reveal the most critical imperfections caused by manufacturing processes. No attempt is therefore made to address a specific type of imperfection but rather treat them all in the combined manner. It has been demonstrated that the morphology of imperfect material systems is well-described by an appropriate set of statistical descriptors. Introducing these descriptors into a suitable optimization environment then provides a tool for the derivation of a PUC that statistically resembles the actual composite system as close as possible. In particular the parameters of the idealized unit cells follow from minimization of the objective function defined as the least square difference of the statistical descriptor related to the original microstructure and to the idealized unit cell, respectively. Once the desired geometrical parameters are determined, the finite element model of a woven composite is formulated and used to predict the overall response of the composite by the numerical homogenization method. The quality of the resulting unit cells is addressed from the point of view of effective elastic properties to examine the applicability and limitations of this procedure and to provide modeling strategy for the analysis of real-world material systems. Although applied to plain weave fabric composites the theoretical formulation presented in this paper is rather general and can be applied to any material systems with disordered or imperfect microstructures.

Perishable Industries from the Windover Bog: An Unexpected Window into the Florida Archaic

Multi-disciplinary excavations at the Windover Bog site (8BR246) in 1986 and 1987 yielded a remarkably well-preserved but very fragile corpus of fiber-based and wood artifacts in direct association with a series of Early Middle Archaic burials. This suite of mid-sixth millennium B.C. materials includes not only the oldest textiles from the American Southeast but also sophisticated basketry, cordage, and wood items previously undocumented (and unanticipated!) at this time horizon in this part of Florida. The textile assemblage includes close-simple and close-diagonal twining, both with S-Twist wefts (paired and trebled); open twining with paired, Z-Twist wefts; and balanced plain weave. Significantly, many of these items are in the form of non-heddle loom-woven cloth. Represented forms include circular or globular bags, hoods, blankets, clothing, and what may be intentionally produced burial shrouds. Also observed are twisted and braided cordage, composite fiber, and fiber and wood construction. The wood assemblage includes a wide array of forms from minimally modified burial “stakes” to complex, extensively worked, “dumbbell“-style mullers. The Windover fiber and wood assemblage is summarized and compared to others in North and South America and the myriad roles of perishable industries are discussed in terms of the lives and deaths of their makers.

An analytical approach to evaluate the coefficients of thermal expansion of textile composite materials

AbstractAn analytical approach is developed to evaluate the coefficients of thermal expansion (CTE) of textile reinforced composites. At the micro level, a cylindrical composite model is employed to model the fiber/matrix thermal and mechanical interactions. The effects of voids and fiber coating on the thermal expansion coefficients of composites are considered at this level. The cylindrical model was then embedded in a macro hybrid finite element solutio structure to calculate the value of the CTE for textile composites. AS‐4/epoxy balanced plain weave textile composites were manufactured. Five different fiber volume fractions were tested for CTE. Evaluatio of the thermal expansion coefficients using the current model was compared to experimental data for in‐plane and out‐of‐plane directions.