Degradation of high‐performance cyanate ester space composites by anodized aluminum

Abstract Cyanate esters are preferred resins for space composites based on excellent mechanical, thermal and dimensional properties. Yet, they are sensitive to co‐reactions with secondary constituents making compatibility a processing challenge. Anodized aluminum mandrels are commonly used for composite manufacturing but deleterious interactions with cyanate ester is not well understood. We investigate here the interaction of anodized aluminum mandrels with surrounding environments and its impact on cure, thermal stability and mechanical properties of M55J/RS3C composites. The uptake and diffusivity of environmental moisture in mandrels was determined gravimetrically and fit to a predictive Fickian model. Cured composite properties were evaluated and correlated with glass transition temperatures (Tg) by dynamic mechanical analysis (DMA), thermal stability by thermal gravimetric analysis (TGA), mechanical properties by flatwise tensile test, and the degradation depth profile by atomic force microscopy (AFM). Parallel to previous results for RS3C but more severe, the degradation penetrated up to 500 μm with reductions of 90°C in Tg, 100°C in thermal stability and 33% mass loss. The inorganic oxide surprisingly absorbs 10× more water at 10× higher rate than composite mandrel materials. The reported results show the anodization presents a unique hydrolysis risk when manufacturing cyanate ester composites so disciplined use and environmental conditioning should be considered when developing space structures. Highlights Cyanate ester composites degraded by anodized mandrels for all conditions. Thermogram signals correlate to composite mechanical degradation. Composite degradation depth gradient determined by atomic force microscopy.