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.