A thermodynamically consistent failure mode dependent continuum damage model with selective damage hardening and deactivation for brittle fiber reinforced composites

This article proposes a three dimensional thermodynamically consistent failure mode dependent continuum damage model for brittle fiber reinforced composite laminates. The novelty also includes the use of selective damage hardening functions, damage model parameters characterization based on all experimental uniaxial/shear stress-strain curves, failure mode switching, and selective damage deactivation algorithms to handle numerical convergence issues due to resulting non-smoothness and non-convexity. The characterized damage evolution equations are used for damage prediction of laminated composite panels using the finite element method coupled with Newton-Raphson method. The proposed damage model is validated against the available experimental results for notched laminated composite panels. The predictions of the proposed model are also compared with a failure mode independent damage model, a phenomenological failure mode dependent damage model and a Hashin failure criteria based model. The results depict the efficacy of the proposed model to capture varying degrees of non-linearity in all experimental uniaxial/shear stress-strain curves. The predicted failure loads for the notched panels are in good agreement with the available experimental results. The results of the proposed model depict different damage intension and compression consistent with strength properties, micro-crack closure/failure mode switching effects, and coupling among damage variables.