A simple modeling approach to predicting damage progress in unidirectionally arrayed chopped strand laminates

Formability, as well as strength and stiffness, is important to utilize carbon-fiber-reinforced plastics (CFRPs) in automobiles for weight saving, because their components have complex geometries. However, the microstructure of composites with discontinuous fibers cannot be controlled when using conventional molding compounds, and therefore, enhancing all the properties is difficult. The unidirectionally arrayed chopped strands (UACS), in which a prepreg sheet with unidirectional and continuous reinforcing fibers is cut in a regular manner, are promising to overcome the difficulty. Although a UACS layer is an assembly of many small sheets, the high structural regularity leads to high mechanical properties. Analytical evaluation of UACS laminates is essential to optimize fiber-cutting (slit) pattern and to achieve better performance, but building a complex mesh near the slits is a severe obstacle. This study therefore proposes a simple approach to model the microstructure of UACS laminates and to predict their damage extension. UACS laminates have two key microstructures, namely the stacked layers and the slit pattern, and the layer-wise modeling and the extended finite-element method (XFEM) are adopted for the laminated structure and the discontinuities owing to slits, respectively. Static tensile strength of quasi-isotropic UACS laminates with diagonal continuous slits was predicted and compared with the reported experiment results. The predicted strength agreed well with the experiments, and the tensile strength of the UACS laminates increased with decreasing the inclined slit angle, owing to the less probability of delamination extension from the slits.