Local Strain Analysis in a Uni-Directional Fiber-Reinforced Composite: DIC Versus FEA

Abstract

This paper presents an experimental and numerical local strain analysis comparison in a Uni-Directional (UD) composite laminate at inter- and intra-ply level under flatwise (through thickness) compression load. The aim of the current study is to understand the load transfer mechanism between different plies by studying the local strain variation in the through-thickness direction. In order to capture the strain gradient within the ply as well as between different plies, digital image correlation (DIC) is conducted on the polished edges of the composite laminate. To capture the local strain variation, contrast to the regular paint speckle pattern, the inherent microstructure of the composite test specimen is used as a speckle pattern for computing the strains. In addition to the experimental strain analysis, numerical micro-level Finite Element (FE) simulations were accomplished. Experimental and numerical strain analyses lead to the following conclusions: (a) the implemented DIC technique is able to accurately capture the strain gradient between the resin-rich regions and the ply both qualitatively and quantitatively; (b) ply outer fibrils closer to the interleave resin region experience the maximum normal compressive strain gradient compared to the fibers within the ply.