Direct observation of plastic shear strain concentration in the thick GLARE laminates under bending loading

Abstract

The results of the digital image correlation (DIC) analysis for the three-point bending tests with GLARE1-9/8 laminates (9 aluminum and 8 unidirectional GFRP layers) are presented in this paper. The findings show that, in samples with a small span-to-thickness ratio, an intensive concentration of the plastic shear strain arises inside the GFRP layers, which significantly affects the load-bearing capacity and apparent interlaminar shear strength of GLARE. Previously, such effects were predicted based on numerical simulations. In the present paper, we validate these theoretical predictions based on the full-field DIC analysis of the shear strain distribution across the GLARE thickness. For this analysis, samples with longitudinal and transverse orientation of glass fibers in the GFRP layers were studied and compared. For the transverse samples, we also found that the matrix cracking in the GFRP layers becomes an additional source for the overall non-linear behavior of GLARE, such that the pure failure mode related to the interlaminar shear cannot be achieved.