Multiscale Simulation of the Mechanical Response of <scp>3D</scp> Carbon Fiber Braided Composites Considering Porosity and Temperature Effects

ABSTRACT This paper investigates how to predict the performance effects and damage development patterns of 3D braided composites at different temperatures and defect volume ratios, especially in complex application scenarios. The novelty lies in presenting a multiscale modeling framework across micro, meso, and macro scales to capture mechanical properties at each level. At the meso and macro scale modeling stage, random defects with a series of volume ratios are generated using the Monte Carlo algorithm in representative volume elements (RVE). Then, a 3D strain‐based Hashin failure model is developed to simulate the macroscopic model failure process in uniaxial stretching. The study focuses on the performance variation of 3D orthogonal braided carbon fiber‐reinforced polyimide composites with stochastic void defects under coupled thermo‐mechanical loading is investigated using the damage evolution theory. The results demonstrate that void defects serve as critical stress raisers that promote crack initiation and accelerate progressive failure. The effect of defects becomes more pronounced as the temperature increases, with the most affected strength decreasing by 54.9%, but the effect of defects is weakened after a certain temperature is reached. Multiscale methods for analyzing the mechanical behavior of composites under the influence of multiple factors offer potential ideas for design optimization.