Cylindrical microplane model for compressive kink band failures and combined friction/inelasticity in fiber composites II: Analyses

This two-part paper presents a novel 3D cylindrical microplane model for the longitudinal compressive failure of fiber reinforced composites by kink band formation. The model formulation was described in part I, and here in part II, its implementation and numerical analyses are described. Through both material point and structure level analyses, the model is shown to predict well the geometric features of the failure, including damage localization, in-plane and out of plane kink band formation, and local fiber rotation. Further, the model is able to capture the entire load displacement curve including the peak load, the prolonged post-peak load plateau, and most importantly, the quasi-brittle fracture mechanics-based strength size effect, in agreement with experiments. The model is also able to capture the effect of the misalignment angle on the peak and post-peak loads. The validated model is used to investigate and quantify the effect of friction on the failure behavior. Results suggest that friction is a major effect, contributing to a higher peak load and post-peak load plateau. Additionally, a simpler and efficient alternative for the combined friction/damage is proposed, which involves a simple modification of the microplane level damage law.