Adhesive Joining of Zerodur–CFRP–Zerodur Sandwich Structures for Aerospace Applications

A high performance adhesive is used to join Zerodur to a carbon fiber reinforced polymers (CFRPs) honeycomb (HC) in a sandwich structure for aerospace applications. The main problem of finding an adhesive with suitable thermomechanical stability and ease of application for use in large components, together with a lower curing temperature than 160 °C, in order to avoid detrimental effects on the CFRPs is resolved. Two phenolic-based and one cyanate ester-based adhesives are considered. One phenolic-based adhesive that is already proven effective in the joining of carbon/carbon composites (C/C) is used to join CFRP slabs and Zerodur–CFRP–Zerodur in a sandwich structure. Thermal analysis is conducted to characterize and compare the phenolic adhesive, cured at 150 °C and at 260 °C, with a cyanate ester-based adhesive and a commercial phenolic-based one. The phenolic adhesive cured at 150 °C results to be the most suitable joining material; the lap shear strength of the CFRP slabs joined at room temperature is measured after thermal cycling. Zerodur–CFRP–Zerodur sandwich structures, joined by the phenolic adhesive cured at 150 °C, are tested in tensile and lap shear modes.