Experimental and numerical investigation of face-core debonding in honeycomb sandwich panels

This work presents an experimental and numerical study to characterise the fracture from debonding between the core and facesheet of honeycomb sandwich double cantilever beam (DCB).The experimental setup was carefully designed to facilitate accurate testing. To simulate the experimental tests, numerical simulations were conducted using a cohesive zone model to replicate crack propagation. An inverse method was used to find out the cohesive properties by correlate the numerical load-displacement curves to the experimental data. Establishing the cohesive strength and fracture energy values allowed for the effective characterisation of the cohesive law for mode I interface fracture. A strong correlation was shown between the numerical predictions and the experimental data for the load-displacement curves. The finite element method (FEM) analysis provided deeper understanding into the stress distribution and delamination behaviour of the joints. The stress analysis at the crack tip indicated that the DCB test involves a mix-mode (I/II) debonding process, with mode I fracture being the dominant mechanism. Furthermore, the study thoroughly explored the crack creation and propagation mechanism at the interface of face and core, providing detailed information on the physical phenomena governing the debonding mechanism in sandwich structures.