Strength prediction in CFRP woven laminate bolted single-lap joints under quasi-static loading using XFEM

Abstract

a b s t r a c tThis paper is concerned with modelling damage and fracture in woven fabric CFRP single-lap bolted joints that fail by net-tension. The approach is based on the assumption that damage (matrix cracking, delamination and fibre tow fracture) initiates and propagates from the hole in a self-similar fashion. A traction-separation law (based on physically meaningful material parameters) is implemented within an Extended Finite Element Method (XFEM) framework and used to predict the joint strength. Reasonable agreement between model and experiment was obtained for test configurations covering different weave types and lay-ups, a range of joint geometries (two hole diameters and a range of normalised joint widths) and finger-tight and fully torqued clamp-up conditions. The greatest discrepancies were for situations where the tensile fracture mechanisms were more complex, and hence not captured fully in the model or when bearing failure occurred.

Experimental Strength of Single-Lap Hybrid Joints on Woven Fabric Kenaf Fiber Composites Under Quasi Static Condition

“…The local failure (bearing stress) initially occurred prior to ultimately net-tension failure. Similar findings were found by Ahmad et al [10] in woven fabric CFRP bolted joints at which intermediate W/d net-tension failure was preceded by local bearing damage with unclamped condition. They also suggested full bearing failures seen to be more pronounce in quasi-isotropic lay-ups compared to cross-ply lay-ups.…”

Crack sensitivity of bolted metallic and polymeric joints

“…Most of these studies are focused on the stress/strain distribution around the fastened hole to predict the crack initiation stress. Ahmad et al [8,9] studied the effect of different seven carbon fiber reinforced polymer (CFRP) woven fabric lay-up configurations on ultimate strength of double-lap bolted joint. They concluded that, the different lay-ups give different stress distributions along the hole boundary angle h, see Fig.…”

“…In addition, surface roughness due to the machining operation will increase the likelihood of a surface fatigue crack initiating and propagating under changing load conditions [7]. Recently, strength prediction of single-lap or double-lap joints failed by net-tension have been studied using different methods such as extended finite element [8,9], cohesive zone model [10][11][12], and coupling techniques between the acoustic emission and digital image [13]. Most of these studies are focused on the stress/strain distribution around the fastened hole to predict the crack initiation stress.…”

Feasibility of mechanical clinching for joining aluminum AA6082-T6 and Carbon Fiber Reinforced Polymer sheets

“…also on the notched strength of the laminate [57]. The joint efficiency of bolted connections made on CFRP/metals hybrid joints typically ranges between 45% -100% [58,59].…”