Determination Of The State Of Stress Between Adhesively Bonded Single Lap-Joints.

ABSTRACT

In this work, the state of stress between adhesively bonded single lap-joints was determined. The state of stress between adhesively bonded single lap-joints was determined by using a linear elastic analysis and experimental testing. In the analysis part of this work, the shear and normal stresses in an adhesively bonded single lap –joints were predicted by subjecting the joint to tension; shear force, and bending moments. Differential equations were used to model the problem and the joint was analyzed using a linear elastic analysis. The solution of the differential equations was used in predicting the shear and normal (peel) stress distributions over the single lap-joint. The boundary conditions used limit the analysis to two adherends having the same thicknesses, lengths, and material properties. In the experimental testing, twelve single lap-joints were produced. These joints were produced using four different overlap lengths(12.7mm,14mm,16mm,and 18mm),and then grouped into three with each group having four single lap-joint of 12.7mm,14mm,16mm,and 18mm overlap lengths. Each of the three groups were subjected to tension, shear force and bending moments by using a universal testing machine and dead weights. The shear and normal stress distributions over the joints were obtained by dividing the applied loads with the area of the overlap region of the joint. It became evident from this work that increasing the overlap length results in an increase in joint strength, and a decrease in both the shear and normal stresses due to an increase in the area of bond. It was also found from this work that maximum stresses occurs the ends of the overlap region of the joint and are hence the critical regions of the bonded assembly. It was also found from this work that the failure associated with single lap-joint are mainly as a result of the failure in the adhesive layer known as adhesive failure. The shear and normal stresses obtained from these tests were in agreement with those obtained from analysis in this work. These tests were used to check the analytical results and to establish confidence in theory. This work could be applied in the determination of the state of stress between adhesively bonded laminated composite door panels.