Curing Modification of Adhesives for Bonding Repairs

摘要

The repairs of metallic aircraft structures with composite patching have been accepted as a reliable technology. The performance of the adhesive plays a key role in the success of such repairs. In order to decrease the thermal residual stress in the structure around the bondline, the curing cycles of high temperature adhesives are modified to temperature lower than their standard curing conditions. There are three high temperature adhesives investigated through curing temperature, degree of cure, and the bonding strength. The aluminum to aluminum bonding and the aluminum to carbon fiber/epoxy composite bonding are carried out to evaluate the curing modifications. The optimized curing conditions are determined for each adhesive based on the bonding strength. The test results show that the curing modifications can decrease the curing temperature 30 to 50 deg C. Such modification can remarkably simplify the field repair processes. A dynamic mechanical method is also applied to evaluate the upper service temperature for each adhesive, in which the storage modulus of torsion test is used as shear modulus. The dynamic mechanical data match well with those obtained from the bonding tests at different temperatures.