Influence of Vacuum and Temperature During Simulated Aging on Properties of a Polyepoxy Adhesive Used in Spacecraft Applications

Adhesively bonded joints used on spacecraft are subject to thermal cycling in orbit. Effect of this ageing is investigated in terms of polyepoxy adhesive properties and corresponding assemblies. A simplified isothermal ageing model is used to understand effect of temperature and secondary vacuum. Vacuum involves the same ageing phenomena than an ageing under neutral gaseous environment at atmospheric pressure. Temperature induces a post-curing of the adhesive. For the highest ageing temperature, a plasticization phenomenon is observed (glass transition temperature decrease). Thermal cycling leads to adhesive’s properties modifications similar to those monitored after an isothermal ageing. The effect of thermal cycle mainly depends on maximum temperature reached during a thermal cycle.