Adhesive joints at high and low temperatures using similar and dissimilar adherends and dual adhesives

Adhesive joints with dual adhesives to be used over a wide temperature range (−55 to 200 °C) were studied theoretically in a previous paper. The joint strength predictions have shown that, for identical adherends, the mixed modulus technique is of little benefit. However, for metal/composite joints, there is a real improvement, especially if the difference of coefficients of thermal expansion is high.The objective of the present study is to investigate experimentally if the use of a mixed adhesive joint is advantageous as predicted. The manufacture is particularly complex, and a way to produce such joints has been described. Experiments are then presented for titanium/titanium and titanium/composite double lap joints. It is shown that, for a joint with dissimilar adherends, the combination of two adhesives gives a better performance (increased load capacity) over the temperature range than a high temperature adhesive alone. Mixed adhesive joints were also cycled thermally to prove that they can be used at low temperatures after a stage at high temperatures, and vice versa.