Tensile properties analysis of CFRP-titanium plate multi-bolt hybrid joints

Hybrid joints have better tensile properties than pure bonded and bolted bolts, and are increasingly used in the aerospace field. Tensile tests are carried out for the Hybrid Bonded/Bolted (HBB) joints of Carbon Fiber Reinforced Polymer (CFRP) laminate and titanium alloy plate under different bolt numbers, and the corresponding load–displacement curves are obtained. At the same time, based on Continuum Damage Mechanics (CDM) theory, which is derived from 3D Hashin failure criteria, and a Cohesive Zone Model (CZM), the tensile strength prediction model of the composite laminate-titanium alloy plate multi-bolted HBB joint was established, and the numerical simulation results were in good agreement with the experimental height, which validate the feasibility of the model. The difference in the bearing capacity of HBB joints under different numbers of bolts is compared and analyzed. On this basis, the influence of inter-bolt distance on the tensile properties of the HBB joints is explored. The results show that the double-nail HBB joints can effectively improve the end warpage and low bearing capacity of the single-nail HBB joints. The tensile failure load of the double-nail HBB joints under the standard lap width (30 mm) is 82.6% higher than that of the single nail, the tensile failure load of the three-bolt HBB joints is 34.1% higher than that of the double nail. For the three-bolt HBB joint, the joint strength is controlled by the adhesive and the external bolt, while the internal bolt is redundant, the hybrid joint can be simplified by reducing the middle bolt. The inter-bolt distance has a great influence on the failure load of the hybrid joint. Increasing the inter-bolt distance can effectively improve the bearing capacity of the structure.