The effect of surface treatments on the interlaminar shear failure of GLARE laminates subjected to pre‐cyclic thermal loads

In this study, both the individual and combined effect of thermal cycling and surface treatment on the interlaminar shear strength (ILSS) of glass laminate aluminum-reinforced epoxy (GLARE) 3/2 sheet material are investigated experimentally. Three kinds of surface treatments including sandpapering, degreasing and both degreasing and sandpapering are applied to AA6061-T6 sheets before manufacturing of hot-pressed GLARE 3/2 sheet material. Two different cyclic thermal conditions, which are referred to the flight characteristics of a typical transport category aircraft, are then applied to short-beam GLARE specimens by changing temperature limits and keeping the number of cycles the same. Three-point bending tests are lastly performed to examine the effects of surface treatments on the ILSS of GLARE laminates under pre-cyclic thermal conditions by comparing with the specimens under acyclic condition at room temperature. The results show that the ILSS of surface-treated laminates have an increase by between 29% and 73% against untreated ones according to the cyclic thermal profile. If sandpapering and degreasing apply together as a combined mechanical–chemical surface treatment process, then ILSS is totally preserved or reduced by only 4% under certain thermal pre-cyclic conditions.