A quantitative evaluation method for void defects stress concentration in woven composites based on Moran's I

Resin-based woven composites have been widely employed in aerospace engineering because of exceptional mechanical properties. However, uneven resin flow and blockage of fiber during processing inevitably entrap air, leading to void defects. Existing models generally treat voids as randomly dispersed and overlook the local stress concentrations caused by void clustering. Moreover, stress concentration has proven difficult to quantify. To solve these problems, Moran’s I was used to quantify the stress concentration effects arising from void clustering. Based on interior, surface, and corner representative volume elements (RVEs), a void insertion method was devised to enable the controllable void distribution. The effects of void location, size, and distribution on the mesoscopic and macroscopic mechanical properties were evaluated. The results indicate that with the void volume fraction of the corner RVE kept constant, adjusting the minimum inter-void distance is equivalent to regulating the void clustering degree. Whether under tensile loading or shear loading, as the void clustering degree decreases, the Moran's I exhibits a decreasing trend, with a corresponding increasing trend observed in the elastic modulus and strength. Therefore, a correlation between the Moran's I and the mechanical properties under different void distributions can be established, allowing the Moran's I to be used to quantitatively evaluate the stress concentration level associated with void distributions.