X-ray CT image-based measurement and modeling of microscopic defects in CFRP laminates

This paper aims to develop a method to measure the microscopic defects in CFRP laminates from X-ray computed tomography (CT) images and a method to introduce the effect of the defects to the finite element method. In the method, voids and fiber distortion are considered. Voids are detected using the difference of the brightness of the X-ray CT images. Fiber distortion is analyzed by processing acquired tomographic images by digital image correlation method (DIC). In order to assess the validity of the proposed method, this study applied the proposed method to a quasi-isotropic CFRP laminate. After X-ray CT imaging, the sample was sectioned and polished. The fiber orientation was then measured experimentally using microscopy. The fiber orientation calculated using the proposed method agrees very well with the experimentally measured one. After demonstrating the validity of the proposed method, we applied the method to the composite lattice cylindrical structure for launch vehicle. This structure was fabricated by a low-cost manufacturing technique. Fiber distortions and voids were measured by the proposed method, and the effect of the defects was introduced to the finite element model. The material properties predicted by the finite element analysis agreed well with the experimental result. The results proved that the proposed method can measure the microscopic defect and can predict the effect of the defect by using FEM.