Flat and Round Nose Low-Velocity Impact Response of Carbon Fibre-Reinforced Laminated Composite Panels Using Energy Approach Coupled With Data Filtering Techniques

Flat nose low-velocity impact response of fibrous composite panels has been investigated by considering energy profile diagrams and associated load–deflection curves. Since fibrous composite based structures are exposed to flat nose impacts during service life, part assembly, and maintenance that inflicts internal invisible damages that cannot be detected during routine inspections, but could cause unexpected catastrophic failure during future operations. Extensive studies are being conducted to improve damage resistance and damage tolerance capabilities of the structures to prevent such failures. Previous studies on the topic revealed that load-deflection based approach works well for the onset of damage. However, flat nose impacts of relatively thick laminates produce level off load-deflection curves once a certain displacement/energy is reached. A very little information is available to extract serious damages from the levelled off loads. Hence, the energy-based approach was employed to quantify the energy absorbed by different mechanisms during flat and round nose impacts of 8- and 16-Ply laminates. Moreover, advanced data filtering techniques were applied to characterize load thresholds and absorbed energies from the levelled off curves. Comparisons of the results showed that the energy-based approach was more suitable for the determination of the initiation, propagation, and accumulated/extent of internal damage.