Search

This study investigates the effect of damage interference resulting from impact loads on the mechanical response and impact fatigue life of E-glass/epoxy composite laminate shells. The analysis involves single impacts at different points to evaluate the impact strength's dependency on boundary conditions. Notably, there is a gradual reduction in both maximum impact force and absorbed energy beyond 10 mm from the centre, towards unconstrained edges, accompanied by an increase in displacement. Specifically, at a distance of 30 mm, the maximum force and absorbed energy register a decrease of 9.4% and 7.9%, respectively, while the displacement rises by 14.5%. The findings reveal that the damage severity decreases as the impact point is closer to the unconstrained edge of the specimen, which can be attributed to a stiffness reduction, which can reach up to 22%. Symmetrically induced pre-damages exhibit no discernible effect on the subsequent impact response. It is observed that beyond 10 mm from the shell's centre, the number of impacts required to reach puncture increases by 10.5% and 21.1% for distances of 20 and 30 mm, respectively. Furthermore, it is also found that alternating impacts between symmetrical points show no inclination towards a preferential point for puncture.

Based on numerical modelling, this study investigates asymmetric semicylindrical composite laminate shells' damage characteristics under low-velocity impact loads. For this purpose, several asymmetric stacking sequences were subjected to low-velocity impact and the results were analysed in terms of force, displacement, contact time, and absorbed energy. It is concluded that the maximum impact force decreases with an increase in the number of layers oriented at 0º, particularly in the upper half of the laminate. The laminates with a 45º orientation in the upper layers present the lowest displacement values, whereas the laminates with the upper layers oriented at 0º exhibit longer contact times. It is also observed that intralaminar damage is responsible for almost half of the total impact energy, followed by delaminations and friction. Stacking sequences with upper layers at 45º exhibit slightly higher energy dissipation due to intralaminar damage (fibre failure) and interlaminar damage (delamination).

The existing literature extensively explores the influence of stacking sequences on symmetric flat laminates subjected to low-velocity impacts. However, this is not true in the case of curved laminates. Therefore, the main goal of this study is to analyse the effect of stacking sequences on the impact response of semicylindrical woven composite shells. For this purpose laminates with [0]8 , [45]8 , [＋15,−15]2S , [＋22.5,−22.5] 2S, and [＋30,−30]2S , were considered in order to evaluate the impact response of layer orientations. Additionally, laminates with [0 2 , 45 2 ]S , [0,45]2S , [0,45 2 , 0]S , and [45 2, 0 2 ] S were employed to analyse the effects of changing the positioning of the layers in relation to the laminate mid-plane. The FE model was validated with the experimental results obtained for [0] laminates, where good numerical–experimental correlation was obtained. The findings suggest that an increase in impact bending stiffness (IBS) leads to a rise in maximum force, accompanied by a decrease in maximum displacement, contact time, and dissipated energy. The primary mechanism responsible for dissipating the majority of impact energy is intralaminar damage, followed by delaminations and friction. Importantly, changing the layer positions has a significant impact on how each layer within the semicylindrical quasi-isotropic composite shell distributes and dissipates energy during the impact event.