Assessing the effects of critical parameters in standoff bonding

Abstract

In this contribution we present the effect of several parameters that are critical for bonding standoffs onto the surface of spacecrafts’ panels with polymeric adhesives. Standoffs are an integral part of the thermal management of space satellites since they ensure that the MLI blankets are mounted and maintained in the correct position during the whole mission duration, including launch. In the recent years, there have been several de-bonding problems during qualification phases, leading to long and costly delays, oftentimes caused from poor design and preparation[1]. For these reasons, we have performed a study of the bond strength of Torlon® 5030 rods bonded over sandwich panels made of an aluminium honeycomb core and CFRP skins. The bond strength was determined by mechanical tests, conducted in tensile and shear modes, both prior and after thermal cycling. Thermal analysis was also performed on the main components under study. The study consists on the following steps: first, different surface treatments of the CFRP skins have been investigated: (i) bonding standoffs with the surface as manufactured, (ii) cleaned with a solvent and (iii) mechanically sanded before cleaning. The best performing treatment was selected and used systematically in the rest of the study. Afterward, different types of adhesives (epoxy, graphene nano-enabled epoxy, polyurethane) and bond-line thicknesses were studied. The findings of this study can help to steer the industry towards better practices regarding the standoff bonding. This will improve the integrity of future space missions.