Influence of adhesive thickness and defect on mechanical property of adhesive bonded joint of flexible polymer substrate and cable for solar panel application

Flexible polymer substrate and flat polymer cable were adhesive bonded to fabricate the solar panel in the present study. The relationship between the adhesive thickness, mechanical properties and fracture morphologies of the joints were systematically investigated to figure out how the adhesive layers with different thickness affected the joints’ mechanical properties. The influence of the defects on the joint quality was also studied via an artificial defect introduction method. Adhesive failure accompanied with low tensile-shear strength was easy to occur to the joints with extremely thin adhesive thickness due to the weak boundary formation between the adhesive and the adherent. When the adhesive thickness increased, the joints started to show the cohesive failure with higher tensile-shear strength since the adhesive completely fill the surface crevices. The joints’ mechanical properties however decreased again with further increasing the adhesive thickness, owing to the generation of more defects and higher residual stress within the thicker adhesive layer. On the other hand, adhesive failure was more likely to occur around the defect, which significantly deteriorated the joints’ mechanical properties. The defect located in the center of the bonding area led to a larger adhesive fractured area, thereby having a greater impact on the mechanical properties in comparison to the same-size defect located in the corner or the marginal center.