Paper number 266

HYGROTHERMAL DEFORMATION OF COMPOSITE SANDWICH PANELS

Ernest G. Wolff, Hong Chen, and Darrell W. Oakes

Precision Measurements and Instruments Inc., Philomath OR 97370 , USA

Summary

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, material moduli and expansion coefficients 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. Tests with both sealed and unsealed edges are analyzed. Diffusion in unsealed sandwich panels, especially with moisture absorbing facesheets and/or cores is non-Fickian and requires a three dimensional analysis to obtain equilibrium data.

Keywords

moisture, hygrothermal, expansion, sandwich, dimensional stability, panels, laminates, absorption.