Study On The Influence Of Recessed Ends On Composite Bonding Joints

The increasingly serious energy crisis and environmental problems on the earth have made automobile lightweight to be an important development direction in the automobile industry.An effective way to achieve this goal is to use new lightweight materials.Composite materials are being widely used in aerospace,automotive and other fields with its low density,high specific strength and specific stiffness,design convenience and other advantages.Bonding is a mainstream method and an effective tool to solve the problems of connection of such materials.In recent years,a large number of scholars have put forward many effective methods to improve the mechanical properties of bonding joints.Based on the previous researches,this paper presents a method of adherend end recessing and mechanical properties of composite bonding joints with this geometry modification are studied based on finite element simulation and experiments.Firstly,2D finite element models of CFRP adhesive joints are established and compared with 3D models and experimental data in the published literature,so the validity of this modeling method is verified.Secondly,influence of recess on the CFRP bonding joints' strength is analyzed by numerical simulation and further study is carried out by extracting adhesive stress distribution.It is found that when peek peel stress at the ends of recessed bonding joints in adhesive reduces effectively,joints' bearing capacity also improves significantly,correspondingly.Two different adhesives are considered in this paper: brittle adhesi ve Araldite? AV138 and ductile adhesive Araldite?2015.Damage variable analysis is also used for better understanding different failure modes.Different overlap lengths are considered and results show that overlap length also influences failure modes,so similar recess shows different effect when bonding length differs.Then,qualitative analysis is given for explanation the above-mentioned phenomena based on previous proposed different strength prediction methods for different failure modes.In order to study the mechanical properties of joints under transverse bending loading condition,the three-point bending models of bonding joints are constructed and the results are also analyzed briefly.Finally,experiments of traditional single lap joints and recessed joints are carried out,also two adhesives are considered.On the one hand it can help to verify partial simulation strength prediction results,and on the other hand differences between experiment and simulation are compared.In this paper,single lap bonding joints with recessed ends are employed,aiming at better mechanical performance compared with traditional joints.Simulation and experiment are both used to investigate influence of recess on bonding joints.Main factors that affect bonding joints' performance,such as overlap length and adhesive type,are considered.And effects of recess on different bonding joints are gotten.This research work has some guiding significance for employing proper methods to improve joints' performance,and certain reference value for deeper understanding of bondline failure modes.