Multi-scale Based Load-bearing Performance Analysis Of Hybrid Bonded-bolted Plain Woven Textile Composite Joints

With the significant applications of composites in advanced industries,the jointing problem of its structures has become increasingly prominent.Besides,the hybrid bonded-bolted(HBB)joint has attracted extensive attention due to its excellent performance advantages.In this paper,a large number of tests and simulations have been conducted to investigate the load-bearing performance of the HBB joints for plain woven textile composite(PWTC)under quasi-static uniaxial tensile conditions,and the effect of lap dimension parameters(including lap length L,lap width W,bolt number N,bolt diameter D,and bolt arrangement)on their ultimate loads and failure modes was analysed systematically.This study provides a theoretical guidance for the application of HBB composite joints in engineering,and has guiding significance for maintaining the integrity of engineering structures,ensuring energy economy and structural safety.Firstly,the microscale and mesoscale representative volume elements(RVEs)of PWTC were established respectively.The equivalent properties of fiber bundles and monolayer layups under periodical loading conditions were predicted by means of the finite element method.Then the mechanical properties of the mesoscale RVE were homogenized into the 0° and 90° subcells in equivalent cross-ply laminate(ECPL)model according to the volume averaging method.Secondly,the macroscale finite element models(FEMs)of the HBB PWTC joints for single-bolt and four-bolt based on the ECPL structure was established to simulate their mechanical responses and damage evolutions under quasi-static uniaxial tensile loading respectively,and the load-bearing mechanism of the HBB joint was revealed.The FEMs were also verified by experiments,and it was found that the experimental and simulation results agreed well in terms of displacement-load curves and damage evolution,which proves the accuracy of the macroscale FEMs and the multiscale approach.Finally,four groups of tests were designed to obtain the load-displacement curves and failure modes of the hybrid joints with different lap dimensions under quasi-static uniaxial tension conditions.The results show that: the ultimate load of HBB joint increase significantly with the lap length and lap width,when the lap length and lap width increased from 15 mm to 25 mm,the ultimate load was increased by a maxmum of 38.3% and 32.6%;and show a trend of first increasing and then decreasing with the bolt diameter,in the process of increasing the bolt diameter from4 mm to 5mm and 6mm,the ultimate load increased by 8.3% and then decreased by1.9%.The rise in bolt number within a specific range also brought an increase in ultimate load,which was increased by a maxmum of 33.7% during the change from single-bolt to four-bolt;besides,the transverse arrangement could obtain higher ultimate load and than the longitudinal arrangement,in the two-bolt and three-bolt joints,the ultimate load in transverse arrangement increased by 13.9% and 2.4%compared with the longitudinal arrangement.The damage of the bond line starts at the boundaries of the joint and then expands to the inside,in this process,it changed from cohesive failure to peeling failure.The failure of PWTC is directly related to the L/D ratio,W/D ratio and the bolt arrangement.The fracture failure and splitting failure can be prevented by increasing the lap width,reducing the number of transverse bolts and avoiding the use of longitudinal arrangement,it can also guiding the occurrence of extrusion failure by increasing the bolt diameter.