Experimental study of strain rate effects on the strength of adhesively bonded joints after hygrothermal exposure

Structural adhesives are increasingly employed by automotive manufacturers in joining components of high strength steels and aluminum alloys in recent years. One aspect still lack of understanding with respect to other adhesive applications is the crash resistance of adhesive bonds after their short-term or long-term hygrothermal exposure. In this paper, the impact rate effect on the strength of adhesively bonded joints after hygrothermal exposure is investigated using single lap-shear coupons. Three substrate combinations of adhesive joints are considered. The joints are exposed under hot-wet conditions, and then tested at three crosshead speeds. The failure strengths and failure modes of adhesive joints are analyzed. A parameter describing impact rate sensitivity is presented to assess the dynamic behaviors of the single lap-shear joints. Experimental results are treated by the two-way analysis of variance method. An analytical approach for representing dynamic strengths of adhesive joints after hygrothermal exposure is proposed.