A Self-Correcting, Thermal-Curvature-Stable Bending Element

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Under a through-thickness temperature variation, thin structural elements such as beams, plates, and shells tend to bend. This bending deformation can distort the elements of a structure and cause thermal stresses. In this paper, the requirements for a laminate which is "self-correcting" are given. These thermal-curvature-stable (TCS) laminates exhibit zero bending curvature under steady-state heat transfer conditions. The TCS effect is independent of the actual temperatures, within the context of linear theory. This effect is demonstrated for an aluminum/composite laminate, where the solution appears as the ratio of composite lamina to aluminum lamina thicknesses. The example laminated beams demonstrate a reduced net in-plane thermal expansion when compared to mono-lithic aluminum beams. The efficiency of the iCS laminate is shown to be more sensitive to lamina thickness than to lamina properties. An additional design parameter for TCS laminates is the fiber volume fraction (Vf), which affects the composite modulus, thermal expansion, and transverse thermal conductivity. It is shown that at higher Vf, the TCS effect is relatively insensitive to Vf. At lower Vf, the in-plane thermal expansion can be further reduced at the expense of increased composite layer thickness.