It must transfer part of the load to the composite patch and hold up under many load cycles
It must transfer part of the load to the composite patch and hold up under many load cycles. Lower temperature is also more suitable because the differences in coefficients of thermal expansion between aluminum and composite materials. Aluminum has a coefficient of thermal expansion much higher than most composite materials, When the aluminum, adhesive, and composite patch system are brought up to temperature, the aluminum will have expanded much more than the composite patch. After the cure time, the system is cooled to room temperature. As of now, the aluminum and composite are coupled as one structure owing to the bond. This causes the specimen to warp and inducing bending stresses into the structure.