Abstract
The use of adhesive has recently been expanding in many fields such as automotive and aircrafts. An adhesively bonded joint, however, has a high stress concentration at the ends of the bond-line and that causes strength reduction. A uniform stress distribution along the overlap is appropriate for improving the load bearing capabilities. As a method to realize the uniform stress distribution, functionally graded adhesive joints have been proposed by a few researchers. The proposed manufacturing method of functionally graded adhesive joints was, however, difficult to control the properties of adhesive such as moduli, elongation and strength. This study presents a novel method to control the properties easier than previous ones. By changing continuously the mixing ratio of two types of adhesive: soft and hard second generation acrylic adhesives (SGA), the adhesive mixture was applied on a substrate. The adhesive layer has graded moduli after the curing at room temperature. In order to evaluate the mechanical properties of the adhesive mixture, bulk specimens were prepared and examined by static tensile tests. Additionally, the hardness distribution of a property graded adhesive layer was measured by the nano-indentation test to confirm the accuracy of the mixing ratio control.
