Strength and failure mode analysis of composite-to-composite and composite-to-metal single lap joints with different surface treatments

Abstract

Adhesives are widely utilized as a part of aviation, automotive, and marine industries. Adhesives are the glue-like materials used to join two surfaces together. Adhesive joints are gradually supplanting mechanical fasteners because they are lightweight structures and thus make an assembly lighter. They also act as a sealant to prevent a structural joint from galvanic corrosion. Adhesive bonds provide high joint strength because the load is distributed uniformly, while in mechanical joints, the load is concentrated at one point, thus leading to stress at that point and in turn causing joint failure. This research concentrated on the analysis of bond strength and failure modes in an adhesive joint. The goal here was to prepare a joint with higher strength. In order to achieve a bond of the highest quality, it is important to consider all parameters required for adhesive bonding. Test results show that a composite-to-composite joint provides higher bond strength compared to a composite-to-aluminum joint. It was concluded that a combination of surface treatments gives better results than only one surface treatment method. Also, it was observed that surface sanding plays a predominant role in enhancing the bond strength. In addition, when plasma treatment of the composite surface and ultraviolet (UV) treatment of the metal surface were combined with surface sanding, the joint strength increased 36.57% in the case of a composite-to-aluminum joint when the aluminum surface was sanded and UV treated for eight days. On the other hand, in the case of a composite-to-composite joint, the joint strength increased 46.02% when the surface was sanded and plasma treated for 12 minutes. Thus, the combination of different surface preparations with sanding, rather than only one type of surface treatment, provides an ideal joint quality.