Effect of Notch-Induced Strain Gradients on the Applicability of Multiscale Approaches for Woven Composites: Combined Experimental and Computational Investigation

Abstract

Woven composites are widely used in the aerospace and wind energy structures due to their high strength to weight ratio and their ability to conform to irregular shapes better than unidirectional composites. These structures frequently contain stress risers such as notches, fasteners, and pre-existing damage, all of which can act as failure nucleation points. The complexities associated with accurately modeling damage initiation and progression in woven composites have led to the development of multiscale models for this class of materials. However, the intrinsic size of the tows in a woven composite is often of the same order as the size of defect features in these structures, which can invalidate many multiscale assumptions that are typically used and have been shown to work well in unidirectional composites. For woven composites, the problem is identified for 12k RVE size by comparing computationally calculated and experimentally determined OHT strengths. In our previous work we utilized a multiscale modeling approach to quantify a critical regime around a hole in an open-hole tension (OHT) test [1]. In the current study we conduct an experimental investigation to compare with finite element analysis. For each OHT test, [0]n and [0/45]ns layup is manufactured. OHT tests are performed for two ratios of hole-size to RVE size. Strains calculated from Digital correlation analysis are plotted across the hole perpendicular to loading directions. These strains and strain gradients are compared with quantities calculated with homogenized model and discrepancies are discussed.