Thermal Warp of Composite Panels

Abstract

Warping due to temperature can be a problem with foam-filled panels since the faces may be held at widely different tem peratures and the faces are not free to ex pand or contract relative to one another. Ex pressions for estimating the warp of such structures have been derived and are com pared to experimental results. Deflections due to thermal warp and simulated wind loads are compared. The warp of panels with thin, flat faces is apparently a function solely of the relative expansion or contraction of the faces, the span, and the thickness of the panel. The stiffness of the faces and the core are important in warp only when at least one face is thick or formed (has an appreciable moment of inertia). Such faces can reduce warp, primarily by inducing shear deforma tion of the core. When they are used in com bination with cores of relatively high shear modulus, little reduction in warp should be expected. While cores of low shear modulus are helpful in thermal warp, they are harm ful to deflection under loads. Formed or thick faces are helpful in both cases.