Abstract:

Automobile lightweight requires the adoption of adhesion technology. However, the hot-humid service environment poses a threat to the mechanical properties of structural adhesives. This experimental study uncovered the effect of hygrothermal degradation (HTD) and drying on an epoxy adhesive and its joint. The tests for uniaxial tensile, notched tensile, double cantilever beam peel and cross tensile peel were conducted to explore the performance of adhesive bulk and joint of varied HTD histories. The result shows that 1) HTD reduced bulk adhesive properties, such as elastic modulus, peak stress, failure strain and energy absorption; 2) Upon drying, elastic modulus and peak stress almost fully recovered; failure strain further decreased; energy absorption hardly restored; 3) HTD reduced the interfacial strength between adhesive and aluminum substrate leading to interfacial failure; 4) Upon drying, the interfacial strength significantly recovered. Therefore, it is suggested to design a bonded vehicle body per the worst case of hygrothermal degradation.

Key words: automobile lightweight, epoxy adhesive, hygrothermal degradation, recoverability, interface