Abstract
The dynamic performance of scarf adhesive joints (SAJs) in fiber-reinforced polymer composites is a new topic that is not available in the literature yet; introducing it is one of the objectives of this study. Changes in stiffness, ratcheting strain, loss factor (tan(delta)), loss modulus (E ''), storage modulus (E '), dissipated energy (Ud), and potential energy (Up) with the number of fatigue cycles were measured at room temperature (RT),-60 degrees C, and 50 degrees C. It was found that fatigue lives were longer at-60 degrees Cthan at RT and 50 degrees C. Fatigue life at plastic strain threshold was decreased by about 98% of the joint lifetime at 50 degrees C. The behavior oftan(delta)agrees qualitatively withE '' andUd. The improved ductility of the SAJs at 50 degrees C induces significant changes inE ' andUp, and hence they can be used to monitor the integrity of the SAJs and early prediction of fatigue failure. At-60 degrees C, theE ' andUpbehave approximately in a linear constant manner up to sudden failure without warning. Accordingly, safe design fatigue life based on time to first failure was applied to evaluate the stress versus number of cycles to failure curves of the SAJs at different reliabilities.