Progressive failure analysis of woven and non-woven CFRP composite/steel bolted joints

Due to recent advancements in textile fabrication, woven fabric reinforcements are used in composite structures as an alternative to traditional unidirectional fiber reinforcing layups. In this paper, experimental work was performed to study the behavior of multiple bolt-lapped joints under uniaxial tension. Different bolt numbers, composite layups, and fabric configurations were studied. Single- and double-lap configurations were used to investigate the effect of secondary stresses. It was found that the P-δ curves of lapped joints exhibit four primary stages: a linear elastic stage, followed by a nonlinear hardening stage, then linear hardening leading up to the peak, and finally a softening stage. For double-lapped non-woven joints, the curves encompass only the first three stages; however, for woven composites, the last stage is very small. In addition, among the laminates, the non-woven laminate sustains the highest normalized failure load, except in the staggered case, where the quasi-isotropic woven laminate exhibits higher strength. Conversely, the bidirectional woven laminate demonstrates the lowest loads and the highest deformation.