A Bimaterial Beam Strategy for Suppressing Thermal Deformation of Arc-Shaped CFRP Ribs via Asymmetric Laminate Design

Deployable reflector antennas demand high geometric precision; the Ruze equation directly links surface error to RF gain. Arc-shaped CFRP ribs are vulnerable to thermal deformation, as their curvature converts in-plane expansion into out-of-plane displacement, which symmetric laminates cannot suppress. Classical laminate theory (CLT) underestimates the coefficient of thermal expansion (CTE) of cross-ply laminates by factors of 1.75-2.38 for the laminate configurations investigated in this study, causing up to 79.4% of displacement prediction errors in symmetric designs. Here, we present an asymmetric laminate that overcomes both limitations. The upper skin (nine plies) and lower/web skins (seven plies) from the same prepreg batch create a CTE mismatch (Δα = 6.30 × 10^-7 K^-1), activating coupling stiffness to generate a thermal moment opposing curvature-driven displacement. Because both skins share identical batch history, CTE prediction errors cancel through common-mode rejection. Compared with the symmetric design, the asymmetric design achieved a 50.4% reduction in thermal deformation (from 210 µm to 104 µm) and improved FEA accuracy from 79.4% error to 4.8% error under experimental schemes. The method uses only conventional 0/90° prepreg and standard autoclave processing, with the upper-surface ply count as the sole design variable for a given section's geometry, establishing retained coupling stiffness as a practical route to dimensional stability in curved space structures.