Strength Prediction Of Composites Based On Unit Cell Analytic Model And Progressive Damage Analysis

Fiber reinforced plastic composites has been widely used in aeronautic, astronautic and engineering projects due to their excellent mechanical performances. The destruction of composite structure often causes huge lives and property damage, so strength is an important problem assessing mechanical properties of composites. Because a composite is a multiphase material, its macro performance is closely bound up with the properties of its micro components, and strength is no exception. In order to give full play to the potential of the composite mechanics, the microstructure of composites is deeply understanded. Thus, the micromechanics-based strength prediction of composites has always been the focus of investigation. Based on this background, an effective micromechanical model is developed for composites, which is has important significance for precdicting strength of composites. It also can provide theoretic guidance for optimization design and performance evaluation of composite structure.In this paper, the strength prediction method is established for composites by combining a unit cell analytic model and progressive damage analysis. This strength prediction method can analyze the stress state of micro components and reveal the damage propagation process as well. Moreover, virtual testing platform is developed for composite mechanical property test using the strength prediction method of this paper, in order to be applied to the engineering. Overall, the main contents of this paper are provided as follows:1. Unit cell analytic model. A representative volume element (RVE) is selected in composite microstructure and used as unit cell model. The unit cell model is divided into the cell of fiber and matrix. Relationship between macro and micro field components is presented through analyzing micromechanics equations, which are based on homogenization theory and continuity conditions of displacements and stresses. Meanwhile, the micromechanics model can realize conversion between macro and micro field components. Then, the micromechanics model was used to predict five independent parameters of several composites by inputting material properties of micro components. At last, predicting results was compared with experimental data and the effect of micro properties on macro performance was analyzed.2. Strength prediction. This paper mainly discusses tensile and compressive strength prediction of unidirectional and multidirectional composites under biaxial loading, in-plane shear progressive damage analysis and strength prediction of composites and open-hole tensile progressive damage analysis and strength prediction of composite laminates. At first,tensile and compressive strength under biaxial loading were analyzed. Elastic and damage performances of the components were passed to the macro composite structures by unit cell analytic model model. The biaxialtension-compression strength envelopes were obtained by computing iteratively until all plies were failure. Predicting results were evaluated using quantitative analysis standard and were compared to some results of world-wide failure exercise. And then, in-plane shear strength was tested by V-notched beam method. Considering the nonlinear shear performance of the matrix, ABAQUS/Explicit finite element method with unit cell analytic model was used to analyze damage evolution process and predict strength of V-notched beam. Nonlinear shear model of matrix was verified by±45°tensile test. At the last, with matrix micro-cracking, progressive damage analysis method was used to simulate gradual damage process of fiber and matrix in open-hole laminates under tension loading. This simulation results were compared with the results without matrix micro-cracking and experimental data respectively. The results have shown that strength prediction method of this paper accord with the fact.3. Virtual testing platform. Numerical simulation of composite mechanical properties based on ASTM standard was established by ABAQUS finite element. Parametric geometric model and optimal numerical model with optimum Materials and damage model were written into the script file of virtual testing. The integration of physical and virtual testing modularization Virtual testing software packages were founded by integrating physical and virtual testing modules. By inputting information about material properties and mechanical property test of composites, numerical model, stress-straincurve and damage contour can be obtained and visualized. Virtual testing system of this paper can provide reliable results and reduce physics experiment and the cost and serve the engineering fields.