Insights into the influence of microstructure on strength and damage progression in carbon/carbon composites

Abstract

Microstructural features influence the mechanical properties and damage progression in advanced materials like Carbon/Carbon (C/C) composites. This study proposes a finite element-based framework to analyze the damage mechanism in unidirectional C/C composites incorporating the effects of fiber arrangement, microstructural defects, and fiber-matrix interface. A 3D Representative Volume Element (RVE) is developed, which consists of carbon matrix, randomly distributed carbon fibers, and pores. The pores in the microstructure are modeled as ellipsoids of varying size, shape, and orientation. Separate stress-based failure criteria and fracture energy-based evolution laws are prescribed for fiber, matrix, and fiber-matrix interface. A user-defined material subroutine (UMAT) is developed in the finite element software Abaqus to implement the initiation and progression of damage in the composite constituents. The homogenized stress-strain response is computed under different loading conditions, namely longitudinal, transverse, in-plane shear, and out-of-plane shear loading. The variation of transverse tensile strength with porosity is also examined, highlighting the influence of pore volume fraction on the mechanical performance of the material. The proposed numerical model is validated through comparison with the Chamis analytical model and with numerical and experimental results from the literature. The proposed framework adopts detailed modeling strategies harnessing the power of computation and individual failure criterion-evolution laws for reliable simulation of damage and strength evaluation of composite materials, which are extensively used in advanced aerospace and engineering applications. © The Author(s) 2025