Junjie Ye

Micromechanical modeling on the rate-dependent viscoplastic behavior of polymer composites with thermal residual stress effect

The research focuses on the effect of thermal residual stress on the rate-sensitive viscoplastic behavior of polymer matrix composites with various fiber cross-sectional shapes. Micromechanical analysis was then conducted to incorporate the inelastic deformation and thermal residual stress into the micromechanical properties of a repeating cell and obtained the macromechanical response of polymer matrix composites by using homogenization theory. The responses of AS4/Polyetheretherketone (PEEK) with circular, square, and elliptical fibers are predicted by the method above at 10−5, 10−1, and 100/s with respect to 15°, 30°, 45°, 60°, 75°, and 90° off-axis angles. The results show that the viscoplastic difference of the response for various fiber shapes becomes more evident with the increase of strain rate. The effect of thermal residual stress varying with off-axis angle is similar to the sinusoidal curve. Besides, the thermal residual stress provides the largest effect on the response with square fiber and the smallest effect on the response with elliptical fiber, which of the effect decreases with the strain rate increasing.

Working temperature variation effect on the failure envelope of continuous fiber-reinforced composites

In this study, a micromechanical method is presented to study working temperature variation effect on biaxial failure envelopes of continuous fiber-reinforced composites with imperfect interfacial bonding. Generalized viscoplastic potential structure model is used to describe nonlinear response of composites. The interfacial debonding model is incorporated into the micromechanical model for describing the interfacial damage evolution. Theoretical results show good consistency with experimental data. On this basis, a series of numerical examples are performed to investigate working temperature variation and interfacial debonding effect on macroscopic tensile response and biaxial loading failure, respectively. The results indicate that the stress–strain responses and failure strength are closely dependent on working temperature. And biaxial compressive loadings in axial-transverse and transverse–transverse, as well as axial tensile and compressive loadings, do not generate interfacial debonding.

Biaxial Yield Surface Investigation of Polymer-Matrix Composites

This article presents a numerical technique for computing the biaxial yield surface of polymer-matrix composites with a given microstructure. Generalized Method of Cells in combination with an Improved Bodner-Partom Viscoplastic model is used to compute the inelastic deformation. The validation of presented model is proved by a fiber Bragg gratings (FBGs) strain test system through uniaxial testing under two different strain rate conditions. On this basis, the manufacturing process thermal residual stress and strain rate effect on the biaxial yield surface of composites are considered. The results show that the effect of thermal residual stress on the biaxial yield response is closely dependent on loading conditions. Moreover, biaxial yield strength tends to increase with the increasing strain rate.

A new three-dimensional parametric FVDAM for investigating the effective elastic moduli of particle-reinforced composites with interphase

ABSTRACT In recent years, the micromechanics model plays an important role in investigating the mechanical properties for particle-reinforced composite (PRC) materials. In this article, through discretizing the representative volume element (RVE) with eight-node hexahedral isoparametric elements, as well as expressing the higher-order displacement functions as the function of surface-averaged displacements for the subcell, a new parametric micromechanical model is presented to investigate the elastic constant variations of the three-dimensional PRC. For validating the proposed method, the finite element method (FEM) is employed for solving the PRC without consideration of interphase. The calculated results by employing the FEM show a good consistency with the proposed micromechanical method. Furthermore, interphase thickness, as well as interphase modulus effect on elastic constant are further predicted and discussed.

Studying the nonlinear properties and strain-rate sensitivity of SiC short fiber-reinforced Al matrix composites

Abstract Stress-strain analysis has been an interesting issue for the mechanical design of composite structures. In this paper, a three-dimensional mechanical model based on generalized method of cells is presented to study the thermal residual stress and loading rates influence on the mechanical responses of short fiber-reinforced (SFR) composites. The effects of the fiber shape on the elastic constant of the SFR were investigated. To verify the prediction method, the calculated elastic modulus was compared with the results of finite element method. On this basis, a unified constitutive model is used to acquire the nonlinear properties of matrix materials. For comparison, SFR composites with and without consideration of thermal residual stress influences on the nonlinear responses are both considered. The results show that the distinct difference for SFR composites can be found at an early stage of loading. Meanwhile, the thermal residual stress influences on the mechanical behaviors present two characteristic stages.

Investigation of the effect of microstructural parameters on the initial yield surface of non-isothermal composites

Abstract In this paper, the effects of microstructural parameters on the initial yield surface of non-isothermal composites were investigated. The fiber phase was assumed to be a linear elastic material, and the matrix was assumed to be a non-linear material. Incorporating the Bodner-Partom viscoplastic constitutive model into a high-fidelity generalized method of cells allowed the initial yield surfaces of non-isothermal composites with different microscopic arrays and fiber cross-section shapes to be studied. Moreover, working temperature effects on initial yield surface are also discussed. The results show that the initial yield stress in the σxx–σyy plane of unidirectional fiber-reinforced composites tends to decrease with increasing working temperature. Furthermore, the effects of fiber arrays and fiber off-axis angles on initial yield stress show similar variation at different working temperature conditions.