A continuum model for predicting strain evolution in carbon fiber-reinforced composites subjected to cyclic loading

The focus of this work is on layered carbon fiber-reinforced polymers (CFRPs) subjected to cyclic loading. The response of CFRPs to cyclic loading is dictated by a variety of mechanisms that come into operation due to repetitive loading. These are quite distinct from mechanisms at play for conventional metals and alloys. Microscopic changes manifest as degradation in properties over thousands of cycles. Due to complex interactions and inherent randomness, capturing the multitude of microscopic effects and collating their effects to manifest as macroscopic changes is a difficult task. Here, the focus is on developing a continuum model which accounts for microscopic changes in an indirect, averaged manner. It is of value as it enables good estimates of material behavior without the need for detailed microscopic information. The intent is to capture the stiffness degradation over the first 10,000 cycles before there are visible changes in the material. For the material under study here, the degradation manifests in the transverse direction earlier than the longitudinal (loading) direction. The model successfully captures this behavior. The model is calibrated against experimental data from the literature.