Multiscale Modeling and Mechanical Performance Simulation of Recycled Carbon Fiber/Epoxy Resin Composites

Recycled carbon fibers can retain a large portion of the mechanical properties of virgin fibers while reducing energy consumption and cost, making them promising for applications. However, the partial removal of surface sizing, the randomness of fiber length and orientation distribution, and the complexity of interfacial bonding can lead to variability in the mechanical properties of recycled carbon fiber composites. In this study, experimental characterization and numerical simulation were combined to investigate the interfacial properties and tensile mechanical behavior of recycled carbon fiber composites. In the experimental part, composites based on epoxy resin and polypropylene matrices were prepared. Microdroplet tests showed that the interfacial shear strength of virgin carbon fiber/epoxy composites was 63.56 MPa, whereas that of recycled carbon fiber/epoxy composites was 56.88 MPa. In the numerical modeling part, a representative volume element model containing fibers, matrix, and fiber/matrix interfaces was established. A brittle fracture criterion for fibers, the Drucker–Prager plasticity model for the matrix, and a Cohesive interface model were introduced to simulate the mechanical response and damage evolution of rCF/EP composites under quasi-static tensile loading. The results show that the simulation results can reasonably reflect the variation trend of tensile strength under different fiber orientation conditions. The experimental fracture morphologies and simulated damage zones show certain correspondence in the main crack paths and damage concentration regions. The established RVE numerical model can provide a reference for analyzing the effects of fiber orientation, interfacial debonding, and matrix damage on the macroscopic tensile performance of recycled carbon fiber composites.