Hygrothermal Deformation of Composite Sandwich Panels

Coefficients of thermal and moisture expansion (CTE and CME) can be predicted for many composite laminates and sandwich panels. Core and adhesive properties, such as geometry and stiffness are important variables. Laminate theory is augmented with a modified model for anisotropic core properties to predict the CTE and CME of sandwich panels. Procedures to measure both CTE and CME are described. Since these are thermodynamic properties, methods to obtain equilibrium moisture strains are needed. Results are given for CFRP facesheets with Al and NOMEX honeycomb cores, and for woven Kevlar facesheets with Al cores. Agreement with predictions is good and depends highly on knowledge of properties of all constituents.