Independent mesh method-based prediction of local and volume average fields in textile composites

Abstract

An independent mesh method (IMM) for three-dimensional stress analysis in composites with complex fiber architectures is proposed. The method represents a combination of direct meshing and voxel-based methodology and allows the modeling of complex tow geometries not readily amenable to traditional finite element meshing. Each fiber tow is meshed independently, while the matrix is meshed throughout the volume of interest. The matrix approximation is then truncated by disregarding the shape functions, whose support is completely inside a tow or completely covered by more than one tow in regions such as tow intersections. The calculation of average stiffness properties of both an oblong fiber-matrix representative volume element (RVE) and a plain weave composite RVE is performed for verification and convergence evaluation purposes. The digital chain technique was used to model fiber architecture in the tri-axial braided composite with high fidelity including the effects of nesting and compaction of plies. Local deformations of the digital architecture due to relief of residual processing stress following a saw cut were predicted by using IMM. These deformations in the tri-axial braided composite were then measured experimentally using Moiré interferometry. The degree of agreement between the predicted strain fields and those measured experimentally was shown to correlate with the degree of accuracy of digital architecture and varied from agreement in average behavior to practically point wise agreement across the entire field of measurement.