Investigation on the tensile performance of pultruded FRP square tube bolted joints based on multi-axial layer design
Based on the optimized multi-axial lay up with regard to the integral structural performance of FRP laminates and bolted joints,this paper further investigated the effects of lay up(uni-axial lay up UD,multi-axial lay up MD1,adjacent uni-axial and multi-axial lay up MD2 and adding carbon fiber into multi-axial lay up BC)and geometric parameters(end distance and pitch)on the axial tensile behavior of pultruded FRP square tube bol-ted joints.The experimental results reveal that adding multi-axial fabrics(MD1 and MD2)significantly enhances the joint ultimate capacity by over 50%and improved the ultimate displacement to more than twice the UD displace-ment,which greatly improves the ultimate capacity and ductility of FRP tube bolted joints.MD2 bolted joint exhibits the highest ultimate capacity,while the utilization of BC don't improve the joint ultimate capacity but increase the joint stiffness by 7%～30%.The UD bolted joints consistently exhibit shear or splitting failure modes regardless of joint geometric parameters.When the end distance-to-bolt diameter ratio reaches 4,the failure modes of multi-axi-al tube bolted joint begin to shift or totally transitioned to ductile bearing failure.The simultaneous bearing process of two bolts is extended with increasing pitch,resulting in the enhancement of joint ductility and ultimate capacity.It is recommended to set the end distance-to-bolt diameter ratio and pitch-to-bolt diameter ratio of the multi-axial pul-truded BFRP tube bolted joint to be no less than 4 in design.
万方数据
维普
