A unified thermo-viscoelastic phase-field fracture model for fiber-reinforced polymer composites

Modeling fracture and damage in fiber-reinforced polymer composites (FRPCs) is complex due to their inherent anisotropic properties and heterogeneous microstructures. The complexities are further amplified under combined thermo-mechanical boundary conditions. In the present work, we propose a thermodynamically consistent, fully coupled thermo-mechanical phase-field fracture model incorporating matrix viscoelasticity to predict rate and temperature-dependent fracture in carbon fiber-reinforced polymer (CFRP) composites. The model predicts the overall load–displacement response and propagating crack paths at transient and steady state thermal environments by employing damage-informed thermomechanical coupling and anisotropic heat conduction. Based on a recently developed theory of phase-field fracture, the diffused phase-field variables are utilized to approximate sharp cracks and interfaces in composite laminates, with the constitutive response of the latter governed by the traction–separation laws. The viscoelastic behavior of the polymer matrix at high temperature is captured through a standard linear viscoelastic constitutive model, and the fibers are considered elastic anisotropic constituents. Using the CFRP’s temperature-dependent viscoelastic characteristics, to demonstrate the predictive capability of the proposed model, a series of benchmark simulations is conducted, including mode-I tensile loading, and strain rate-dependent tests on CFRP lamina at elevated temperatures. The model is further applied to investigate the effects of fiber orientation on crack propagation and temperature evolution under pure thermal and coupled thermo-mechanical boundary conditions. Additionally, we analyze the interaction between bulk cracking and interfacial delamination in laminated composites, subjected to thermal and mechanical boundary conditions. The results show good insight into expected failure mechanisms, highlighting the model’s effectiveness in capturing complex crack interactions, rate-dependent fracture, and thermo-mechanical coupling effects in CFRP fracture.