Investigation on the mechanical properties of epoxy resin with void defects using digital image correlation and image-based finite element method

Fiber-reinforced polymer composite structures are increasingly used as load-bearing components in aerospace and automotive industries. The precise mechanical properties of composites are essential for structural design and analysis. Void defects, which are caused by the curing process of resin matrix, greatly impact the overall performance of composite structures. In this study, a novel image-based finite element modeling algorithm is proposed to acquire the real three-dimensional topography of void defects, including micro X-ray computed tomography scanning, image processing, non-uniform rational B-spline reconstruction and Boolean logic operation. This new algorithm can solve the reconstruction of blurry tomographic slices. Epoxy resin specimens embedded with a low-density expanded polystyrene bead as void defect were fabricated and tested with a digital image correlation system. By using the developed modeling method, the effects of void defect on the ultimate strength, Young's modulus, damage mode and strain field distribution of specimens were analyzed and compared with experimental data. Results revealed that the real geometry of the void defect must be accounted for to obtain the maximum stress accurately.