Forming-behavior characterization of cross-ply carbon fiber/PA6 laminates using the bias-extension test

This work focuses on the in-plane shear behavior of carbon fiber-reinforced polyamide 6 cross-ply laminates. Bias-extension tests are performed at different temperatures and deformation rates. Forming behavior is compared with the prediction of the pin-jointed net (PJN) idealization, and the effects of temperature and deformation rate are investigated. A key objective is to estimate the locking angle of the material. The results show that the shear behavior is comparable to the one of woven fabrics for limited deformations, with the PJN holding up to a shear angle of 30°. The load required to deform the specimens is higher for lower temperatures or faster deformation rates, and the locking angle of the material is 45°. After locking, fiber slippage and compaction are significant rather than inter-ply fiber rotation prior to the locking angle. Moreover, the deformation localization shows that heterogeneities in the shear pattern are more pronounced at the lower deformation rates. Although the average shear angle measured in the bias-extension test is not affected by the deformation rate, the localization of shear deformation at lower deformation rates causes a higher variability of the shear angle within the test.