Adhesive Joint Characterization by Ultrasonic Surface and Interface Waves

Characterization of adhesively bonded joints using acousto-ultrasonics

“…According to Rokhlin [31,32], the change in elastic modulus of the modified epoxy adhesive (such as the one used in present study) with temperature is due to the known thermomechanical behaviour of polymers which, at high temperatures, behave as a low-modulus, rubber-type material while, at low temperatures, show the behaviour of a high-modulus, glass-type material. Since the cohesive strength of a given material correlates with its elastic modulus, a change in the elastic modulus of the material is normally associated with a corresponding change in strength [31,113].…”

“…Since the cohesive strength of a given material correlates with its elastic modulus, a change in the elastic modulus of the material is normally associated with a corresponding change in strength [31,113]. Hence, as the elastic modulus of a polymeric adhesive decreases with increasing temperature, it is expected that the cohesive streng•...!.…”

“…Rokhlin [31][32][33] investigated the application of ultrasonic surface and interface waves for evaluation of thin interface layers, in particularly, adhesively bonded structures. His arguments are that the interface waves produce shear stresses at the interface which are sensitive to variations in the adhesion quality .…”

“…Chapman [35] used a commercially available bond tester which relied on the plate waves (Lamb waves) to quantify the bond quality of fibreglass reinforced plastic bonded joints. Rokhlin [33] discussed the use of Lamb waves method to evaluate adhesive during curing, whereas Pike and Williams [36] studied the effect of cure temperature and heat-up rate on the performance of adhesively bonded honeycomb structures using the ultrasonic plate wave technique.…”

“…as a function of aging time of the adhesive film. The scatter and the average value of the five data points of each group is shown in the Figure. As the aging time of the adhesive increases, the joint strength is expected to decrease because for an extended period of aging, the adhesive film becomes more polymerized and does not convert to the fluid during the curing process and therefore bond formation will not be effective [33]. However, as illustrated in Figure 5.28, the joint strength shows a reduction of only about 15% for the aging time of 8 weeks in room temperature.…”