Characterisation of bonded-repaired sandwich composite facing sheet using multiscale modelling and experimental testing

Abstract

Prediction of composite materials failure is a valuable resource for ensuring structural integrity of aerospace structures. A Multiscale Modelling (MsM) approach was developed with the objective to characterise the failure of a bonded-repaired Sandwich Composite Facing Sheet (SCFS). Failure characterisation of the carbon fibre SCFS was conducted for a four-point beam bending setup under static and fatigue loads.The MsM approach bridged three different finite element models across three length scales: from micro scale to meso scale and from meso scale to macro scale. The data processing and information transfer between the scales was facilited by Microsoft Excel Visual Basic for applications (VBA) scripts.For the experimental part of the study bonded-repaired sandwich composite facing sheet specimens were tested in a four-point bending setup. The specimens were manufactured and tested in a certified aircraft manufacturing facility to guarantee good quality. Comparisons of micro, meso and micro scale results were presented for both MsM and experimentation to validate the proposed MsM failure characterisation approach. Numerical and fractographical results from MsM and experimentation matched very well for the macro and meso scale but matched to a limited level for the micro scale. The limitation of obtainining progressive failure experiment data at the micro scale hampered this study. In general the MsM failure characterisation approach performed well against the experiment. It presents an opportunity to use an alternative composite materials failure characterisation method for future research.