Process induced deformations in composite sandwich panels using an in-homogeneous layup design

Abstract

This work presents an experimental and numerical study of process-induced deformation (PID) in flat sandwich panels with in-homogeneous ply layups. An over-expanded Nomex honeycomb core and aerospace-grade prepreg was used to manufacture sandwich panels using the autoclave technique. Process-induced spring-in and warpage at different locations were measured. A 3D FE analysis was performed for the full cure cycle. The FE model successfully captured the shrinkage due to cure, anisotropic and thermo-physical properties of the sandwich structure and tool-part interactions. The computed maximum spring-in values obtained from the FE model were in good agreement with average spring-in values measured experimentally. An overall error of less than 2% was found in the PID of the sandwich panel. The effect of tooling material and core material on PID was also investigated. The numerical results suggest that an aluminum tool and an aluminum core could potentially reduce warpage in the sandwich panel studied.