Multiscale Analysis of Stitched CFRP Composites Including the Effect of Geometrical Imperfection

Abstract

In this paper, multiscale analysis is conducted for through-the-thickness stitched CFRP composites in order to investigate the effect of unintended imperfections in the microstructure. The analytical method is based on the homogenization method, and the effect of the imperfection is introduced by using perturbation method. Throughthe- thickness stitched CFRP laminates have prominent mechanical properties such as higher delamination toughness, better impact resistance under low-velocity impact, and higher CAI strength than that of non-stitched laminates. However, through-thethickness stitching process inevitably induces microscopic geometrical imperfection such as fiber waviness and resin pocket. Therefore, in order to analyze material behavior precisely, the evaluation of the effect of the imperfection is essential. In this paper, the effects of the imperfection on the macroscopic material properties and on the microscopic stress distribution are both analyzed by using multiscale analysis. The multiscale simulation method is based on the homogenization method. Geometrical imperfection is considered by using perturbation method, and it is introduced as an input to the calculation. The calculation to analyze the effect of the imperfection is always done using the idealized perfect geometry. In this study, several realistic geometrical imperfection patterns in the stitched CFRP composite are measured by using sub-micro focus X-ray CT devise, and they are used as inputs to the calculation method. The calculated results are compared to the experimental results. Simulation results reveal that the microscopic geometrical imperfection significantly affects the macroscopic material properties and microscopic stress distribution of the through-thethickness stitched CFRP composites.