Research On Stress Distribution And Strength Of Glass Fiber Reinforced Composite Adhesively-bonded Single Lap Joint

Adhesively bonded joints have obvious advantages compared to traditional mechanical joints because of their lightweight and cost efficient properties and are widely used in aerospace,marine and automotive structures.The use of adhesively bonded joints is the most suitable approach for joining composite structures as compared with the use of bolts and mechanical joints.By using single lap joints(SLJs),the stress concentration has been reduced while maintaining the structural integrity.In addition,it can increase fatigue durability and corrosion resistance.But in practice,the joint strength will be affected by many factors,which hinder the further application of SLJs.Therefore,it is of great significance to systematically study the stress distribution and strength prediction of single lap joints.In this paper,the composite single lap joint as the research object.First,the research background and significance are described,and the literature related to the SLJ at home and abroad are reviewed and summarized.Then,the adhesive stress distribution and joint failure load are discussed based on the analytical model and finite element(FE)method.Next,the strength of the interface point of SLJs is analyzed based on singularity theory.Finally,FE models and experiments of composite SLJs with different adhesive defects have been developed to evaluate the influence of the adhesive defects in the composite SLJs.More details is as follows:(1)Strength prediction and stress analysis for single lap joint based on analytical model and FE simulationFirst,a stress analytical model for adhesive single lap joint is created.Then the validity of this model was verified by plane FE simulation of the SLJs.A three-dimensional FE models of composite SLJs have been conducted to understand the stress distribution of the composite SLJs subjected to tensile load.Finally,a few failure load prediction methods are compared with the experimental data.The results show that increasing the lap length helps to improve the load-carrying capacity of the SLJs,and the load-carrying capacity increases first and then decreases with the increase of the adhesive thickness.(2)Analysis of the strength of the interface point of SLJs based on singularity theoryThe singular stress filed and strength of the SLJs is studied based on the singularity theory.The singularity order and stress intensity factor of the interface point are analyzed.The effects of the main local geometric characteristics of the SLJ,such as spew-filter,overlap length,adhesive thickness and adherend chamfering,on the singular stress filed are studied,and general conclusions are given.(3)Stress analysis of a composite single lap joint with defects based on FE simulation and experimentThree-dimensional FE models and experiments of composite SLJs with no adhesive defects have been conducted to understand the failure of the composite SLJs subjected to tensile load.Then,FE models of composite SLJs with different adhesive defects have been developed to evaluate the influence of the adhesive defects in the composite SLJs.Four types of adhesive defects with different defect sizes and shapes,such as shapes in circular,square and rectangular,in the lap region are considered.The dissertation researched the stress distribution,singular stress filed,static strength and its influencing factors based on FE simulation,analytical model,singularity theory and related experiments.The results provide guidance for the application of single lap joints in practice.