Failure Properties of Bolted Joints in Pultruded CF/GFRP Laminates
Takeshi KISHIMA and Tetsuya WATANABE
Abstract:The failure loads of FRP bolted joints depend on the failure mechanisms reflected in the failure modes. The aim of this paper is to obtain the failure properties of bolted joints in pultruded CF/GFRP laminates based on the experimental results. The failure modes are divided into bearing, shear-out, tension, shear-tension and bearing-tension failures and the latter three modes are with the net-tension failure of outer layers. Bearing failure could be ductile due to continuity of the compressive failure decreasing the stress intensity and depend on both compressive failure progress and out-of-plane shear failure. Shear-out failure could be ductile due to both decrease in the shear stress intensity for outer layers and stress redistribution among layers during failure progress, and its load could increase with the ratio of width or edge distance to bolt diameter when the loading stress at failure is out of relation to them. Bearing and shear-out failure loads could depend on the volume fraction of outer layers, that is, they could decrease with decreasing volume of outer layers for compressive failure less concentrated on loading point and relatively linearly with for more concentrated. Tension failure load could depend on edge-side interlayer delamination, suggesting that it could appreciably decrease for the small volume of outer layers due to increasing compressive stress and not largely depend on that volume for the thorough delamination of unidirectional layer due to the extremely higher stress at loading point than around by non-restrictive interlayer shear deformation. Shear-tension failure load could increase with the volume fraction of outer layers and bearing-tension for the thorough delamination of unidirectional layer almost linearly with, due to the compressive stress depending on the interlayer property. Key Words:Bolted joint, CF/GFRP laminate, Failure mode, Failure load, Width, Edge distance, Volume fraction of layer, Compressive failure progress