Parametric Microscopic Modeling And Damage Analysis Of Continuous Fiber-Reinforced Composites

With the rapid development of science and technology,composite structures have evolved from non-load-bearing components such as wing skins,to main load-bearing components such as aircraft tails.Due to the poor service environment,many accidents caused by composite failures can be found everywhere.Classical mechanics of composite materials mainly analyzes the mechanical behavior of composite materials from a macroscopic scale,ignoring microscopic factors(such as matrix cracking,etc.).Therefore,it is difficult to reasonably reveal its failure mechanism.However,the existing composite micromechanics is difficult to reasonably and efficiently complete the analysis of related problems,which restricts the application of micromechanics in practical engineering.It is urgent to establish an effective microscopic mechanical model to analyze the damage evolutions and failure behaviors of composites at the micro-scale.For continuous fiber-reinforced composite materials,a quadrilateral parametric unit is constructed at the micro-scale,and the repeating unit cell(RUC)of the composites is discretized by employing the parametric unit.The proposed parametric modeling scheme overcomes the stress concentration between the fiber and the matrix,which is caused by the rectangular elements in the original method.On this basis,the Parametric Finite-Volume Direct Averaging Micromechanics(Parametric FVDAM)is established by using the continuity conditions of stress and displacement between adjacent elements as well as periodic boundary conditions.The model is used to study the micromechanical behavior and microscopic damage evolution of fiber-reinforced composite materials,providing theoretical basis and technical guarantee for engineering applications such as structural design optimization,mechanical performance analysis and safe use of fiber-reinforced composite materials.The specific research content is as follows:A micromechanical analysis model is established for fiber-reinforced composite materials by using parametric FVDAM theory.In the procedure of microscopic modeling,the basic idea of parameter mapping is employed to construct arbitrary convex quadrilateral elements in order to eliminate the stress concentration between the fiber and the matrix caused by rectangular sub-cell elements.Moreover,The established model is used to analyze the equivalent modulus and micro-stress distributions of fiber reinforced composites.The numerical results are indicated that the proposed method show a good agreement with finite element method and high-fidelity generalized method of cells(HFGMC)solution to verify the feasibility of the model.An improved unified viscoplastic Bonder-Parton model is introduced to describe the nonlinear behavior of the matrix material.A nonlinear micromechanical model of the fiberreinforced polymer matrix composites is established.Fiber volume content and loading rate influence on their mechanical behaviors are investigated.The relationships between microcracks and nonlinear mechanical behaviors of continuous fiber-reinforced composites are both discussed.In order to investigate the micro-damage evolution of the continuous fiber-reinforced composite materials,a microscopic progressive failure analysis model is proposed by introducing a sudden drop stiffness degradation model into the representative volume element.By combining with the failure criteria,the micro-crack propagations of the continuous fiber-reinforced composites under different loading modes were studied.The failure mechanisms are further revealed.