Functionally graded adhesive joints by graded mixing of nanoparticles

The main objective of the present study was to use a functionally modified adhesive in order to have an adhesive with properties that vary gradually along the overlap, allowing a uniform stress distribution along the overlap. This allows for a stronger and more efficient adhesive joint. It is possible to work with much smaller areas, reducing considerably the weight of the structure and obtaining more reliable joints. The adhesive stiffness would vary along the overlap, being maximum in the middle and minimum at the ends of the overlap. The processes tested in this work were dielectric heating using a domestic microwave oven and conventional oven heating. Different amounts of carbon black were used and functionally dispersed along the bondline length in order to obtain a functionally graded joint. The functionally graded joints were found to have a higher joint strength compared to the cases where the carbon black was dispersed uniformly along the overlap or where the adhesive was used without carbon black. An analytical model was used to assist with the prediction and the assessment of the possible effectiveness of a graded joint concept.