Research On The Mechanical Behavior Of Multi-Rivet-bonded Hybrid Joint Between CFRP And Aluminum Alloy Sheets

Lightweight is one of the most effective technology approach for energy saving and emission reduction of vehicles.Carbon fiber reinforced polymer(CFRP)has some features,such as low density,high specific strength,and good fatigue resistance,and it has a good effect on the lightweight of vehicle.However,with the increasing demand for multi-material and lightweight structures for vehicles,the connection between CFRP and aluminum alloys(Al)has received increasing attention.Both bonded joint and mechanical joint can achieve the connection between CFRP and Al effectively,but the bonded joint has instantaneous failure characteristics,and the prefabricated holes of the mechanical joint will weaken the property of CFRP.Therefore,the rivet-bonded hybrid joint is a better choice that can be considered.It constitutes the theme of the research of this article,especially for systematically researching the hybrid connection technology consisting of multi-rivet joint and bonded joint.Firstly,the theory of elastic-plastic mechanics was combed to understand the mechanics theory of CFRP laminates.The common failure criteria and stiffness degradation criteria of CFRP were summarized.And then the CFRP plates were fabricated by autoclave process.Secondly,The CFRP,5052 aluminum alloy and 2A10 aluminum alloys were tested for material properties of CFRP/Al multi-rivet joints.The relevant mechanical property parameters were obtained,which laid the foundation for the three-dimensional cumulative damage failure finite element model.The finite element model of CFRP/Al rivet joints were established by using Hashin failure criterion and Ductile failure criteria.The results of the simulation of single lap joints and T joints were compared with the test results to verify the validity of the finite model.Based on the model,the performance of single-rivet,double-rivet and multi-rivet joints are compared and analyzed.At the same time,the influence factors of joints were analyzed,and the effects of rivet diameter,pitch distance of rivets and row distance of rivets on the mechanical property of joints were systematically studied.Subsequently,the finite element model of CFRP/Al adhesive bonded joint was established based on the cohesive zone model,and the validity of the model was verified by experimental result.The stress distribution and fracture form in the adhesive layer were analyzed by simulation,and it was found that the thickness of the adhesive layer and the overlap length of the joint had a greater influence on the shear strength,but the impact on the peel strength was relatively small.Then,the method of adhesive solidificating after pressure riveting has been chosen to complete the rivet-bonded joint.Through testing and simulation,it is found that the rivetbonded joint has greater shear strength and peel strength,and it has a better energy absorption.The hybrid joint was conducive to the improvement of structural crash resistance,and it could provide a certain reference for the engineering application.Finally,the multi-objective optimization analysis was to take the shear strength and peel strength of the rivet-bonded joint as the objective.The orthogonal test method was used to obtain sample points to create an approximate model,and the RSM Model,the RBF Model and the Kriging Model were compared to find that the RBF model has a better fitting effect.Using the established approximate model,the Pareto frontier of the rivet-bonded joint was obtained by using the NSGA-II multi-objective optimization method.The optimization results were verified by simulation and the effectiveness of the optimized scheme was ensured.