Micromechanical Modeling and Damage Mechanism Analysis of M55J High‐Modulus Carbon Fiber Composites With Diverse Fiber Arrangements

High‐modulus carbon fiber composites are widely used in aerospace and other fields, but their macroscopic performance prediction and damage evolution mechanisms remain insufficiently understood. In this study, based on experiments and micromechanical finite element models (FEMs), standardized mechanical tests were conducted to obtain the elastic parameters of M55J carbon fiber‐reinforced cyanate ester matrix composites (M55J/CE), including a longitudinal modulus of 331 GPa, a transverse modulus of 6.2 GPa, and an in‐plane shear modulus of 3.8 GPa. Subsequently, representative volume elements (RVEs) with square, rhombic, hexagonal, and random fiber arrangements were constructed by introducing interphase layers and defining phase constitutive behaviors, to predict the macroscopic elastic properties under periodic boundary conditions (PBCs). Comparing with experimental data, it is found that the Chamis model and the four RVE models have excellent prediction accuracy, with all RVE models achieving over 90% accuracy. Among them, the random RVE model performs best overall, with prediction accuracies for the three moduli being 99%, 98%, and 97% respectively. Further damage evolution analysis reveals that the primary failure modes for longitudinal tensile loading are interfacial debonding and brittle fracture of fibers, which are independent of the fiber arrangement. For transverse tensile and shear loading, the main failure modes are matrix cracking and interfacial debonding, and failure typically initiates in fiber‐rich regions.