Multi-impact behaviour of composite laminates under constant and different energy levels

Composite laminates have been used in the most diverse engineering fields, in which they are often subject to multi-impacts. Typical examples of these phenomena are found in the wind energy industry. However, several studies have focused on this subject, but most involve events with the same energy level. Therefore, this work intends to study the multi-impact behaviour of composite laminates as well as to verify if a linear damage accumulation law can predict the multi-impact life. For this purpose, low-velocity impact tests were carried out with impact energies of 4 J, 6 J, 8 J and 10 J. From the study carried out for single impacts, it was possible to observe that the damaged area increased by around 151.2%, promoting higher impact loads, displacement, and impact bending stiffness for higher impact energy levels, while the restored energy decreased. In terms of multiimpact strength, the classic SN curve was adopted, and the number of impacts to failure varied inversely with the impact energy. Finally, in terms of multi-impact behaviour under different energy levels, the lives resulting from experimental tests and estimated lives based on Palmgren-Miner's Law did not find a good agreement.

Automated summary

This study investigates the multi-impact behavior of composite laminates and finds that the damaged area increases with higher impact energy levels, resulting in higher impact loads, displacement, and impact bending stiffness. The number of impacts to failure follows an inverse relationship with the impact energy. However, the experimental results do not agree with the estimated lives based on Palmgren-Miner's Law.