Assessing the compression after impact behaviour of innovative multifunctional composites

In the present work, the synergistic effect of multiwalled carbon nanotubes and glycidyl polyhedral oligomeric silsesquioxanes on the compression after impact behaviour of multifunctional carbon fibre–reinforced epoxy composite plates is investigated. For the qualitative evaluation of the damage accumulation after impact, non-destructive ultrasonic C-scan tests were performed. The impact-induced material degradation was correlated with data obtained from C-scan graphs through applying the concept of the damage severity factor. The test results obtained from C-scan analysis have shown a significant increase of the damaged area after the impact tests, as compared to the unfilled material considered as ‘reference’. A reduced compression after impact strength is observed for the enhanced material as compared to the reference material. To identify the type of damage, optical microscope, scanning electron microscope and energy dispersive spectroscopy analyses were made after the tests. The optical microscope analysis has shown more extended cracking and delaminations for the enhanced material. Scanning electron microscopic analysis has revealed the presence of carbon nanotube agglomerates and possible glycidyl polyhedral oligomeric silsesquioxanes aggregates which might be the cause for a degraded compression after impact behaviour of the multifunctional composites.