On joint strengths, peel stresses and failure modes in adhesively bonded double-strap and supported single-lap GFRP joints

This paper presents the results of an experimental investigation conducted to characterize the joint strengths, peel stresses and failure modes in adhesively bonded double-strap and supported single-lap glass fiber-reinforced polymer (GFRP) joints. The joints were composed of pultruded GFRP adherends having the same stiffness as the members that would be used in FRP bridge decks. The design parameters investigated in the study were adhesive type, adhesive layer thickness and overlap length. The load–displacement response and joint strength of double-strap joints were compared with those of supported single-lap joints to show the superior strength characteristics of double-strap joints over supported single-lap joints. It was shown that the joint strength was almost independent of adhesive type, decreased with the adhesive layer thickness and increased with overlap length. Most specimens exhibited the thin-layer cohesive (TLC) failure pattern or the light-fiber-tear (LFT) failure pattern. The peeling effect was crucial to the failure behavior of adhesively bonded joints.