Real Time Identification of Interfacial Delamination in Sandwich Composite Through Point Sensing: Experimental Finding on Crack Propagation Morphology

Abstract

Real time delamination propagation profile within the interface between the skin and polymer foam core of sandwich panels has been experimentally mapped with fiber optic Bragg grating (FBG) sensors embedded within the interface of pre-cracked double cantilever beam (DCB) specimens subjected to mode I dominated loading. Load-deformation is recorded from universal testing machine (UTM), crack-front propagation visible on the side of DCB is recorded from a camera attachment and the real time spectral data of sensors with wave length division multiplexing are recorded by interrogator. The crack propagation profile is mapped from the shifts in peak wavelengths of FBGs at different locations. The real-time crack propagation profile is mapped from the positions of crack-tips in parallel channels of FBGs. The results indicate non-rectangular non-parabolic profile and raises question on assumptions of numerical simulations for crack propagation problems of these types of sandwich composites.