Effect of thin skin architecture and curing process on the mechanical response of composite sandwiches under low velocity-impact loading

A multiscale analysis on the effect of skin architecture and curing process influences on the mechanical response of double-clamped sandwich composites under low-velocity impact (LVI) is carried out. The specimens are constituted of a foam core surrounded by thin carbon/epoxy skins made by automated fiber placement (AFP). Two curing processes, nine lower skin architectures with isostiffness in uniaxial tension, and three levels of energy have been compared. Results were examined at a macroscale by using the maximum contact force and the maximum impactor displacement, and at a mesoscale by performing stereo digital image correlation (DIC) on the speckled lower skin followed by a fast Fourier transform (FFT) analysis. Both curing processes and skin archi-tectures play a role in the global mechanical response, which is confirmed by the finer insight provided by optical measurement methods. The use of the Fourier transform and its limitations are proposed to reveal architectural effects with amplitude of the same order as the measurement noise.