Enhancement of structural integrity of stitched sandwich panels: Investigation by flexural, low velocity impact, compression after impact, and machine learning methods

The performance of the developed Stitched Foam-filled Honeycomb Sandwich (SFHS) panels with two different stitches spacing were compared to the Foam-filled Honeycomb Sandwich (FHS) panel. The adjacent Stitched Foam-filled Honeycomb Sandwich (SFHS1) panel exhibited a peak flexural load of 1672 N at a strain rate of 100 mm/min, achieved a velocity of 4.031 m/s during Low Velocity Impact (LVI) testing, and demonstrated a compressive strength of 14.19 N/mm² in Compression After Impact (CAI) tests performed with a maximum drop height impactor of 700 mm. Matlab image processing was utilized to detect damaged areas that were invisible to the human eye after the LVI test. The experimental data of CAI tests were subjected to a Machine Learning (ML) third-order regression algorithm that predicted SFHS1 and alternate Stitched Foam-filled Honeycomb Sandwich (SFHS2) panel would withstand up to a drop height of 1300 mm at 885 N and 845 N respectively, whereas value is far less for FHS panel. The results showcased the effectiveness of through-thickness stitching reinforcement in improving the panel's interfacial, flexural, residual compressive, and impact strengths compared to unstitched panel. The study emphasized the advantage of implementing the SFHS1 panel, which is affordable and lightweight, which makes it appropriate for a wide range of structural applications.