How free-edge effects impede CTE determination for composite laminates

Abstract The determination of in-plane coefficients of thermal expansion (CTEs) of full-stack composite laminates by means of thermo-mechanical analysis (TMA) is affected by free-edge effects. A numerical study has been performed, which is focussed on the quantification of the effects of TMA sample size, laminate layup and the presence of discrete interleaf layers on the determined laminate CTEs. Fine finite-element (FE) meshes have been used to visualize and to examine free-edge effects. The study results call for carefulness when CTEs of full multi-angle laminates shall be determined by means of TMA. When the typical sample dimensions of a few millimeter are used CTEs will likely be overestimated.