Impact response of laminated cylindrical shells

Abstract

Composite laminates subjected to low-velocity impact events on the through-thickness direction are conveniently studied and disseminated in the open literature. However, in terms of laminate cylindrical shells this subject is less common. Therefore, the main goal of the present work is to study the impact response of laminate composite cylindrical shells composed by different type of fibres. For this purpose, laminates with different configurations (6C, 2C+2K+2C and 2C+2G+2C), where the "number" represents the number of layers used and C=Carbon, K=Kevlar and G=Glass fibre layers, were analysed in terms of static and impact strength. It is possible to conclude that both static and impact performance are strongly influenced by the shells' configuration. In terms of compressive static strength, the Kevlar hybrid shells present values 53.2% higher than the 6C shells, while the glass hybrid shells present values 17.3% lower. The impact analyses shows, regardless the similarity of the maximum loads for all configurations, that Kevlar hybrid shells achieved the highest elastic recuperation and the glass hybrid shells the maximum displacement.

Impact Response of Composite Sandwich Cylindrical Shells

“…In terms of damage mechanisms (see Figure 5), the failure analysis shows fibre fractures, which started in the fibres under compression, and some delaminations around the broken fibres. All these failure mechanisms arose in the indenter/composite contact region and agree with the literature [42,47], where the compressive stress concentration at the loading nose contact region associated with the low compressive strength of the fibres promotes the failure damage described above. For example, Figure 5a shows the failure mechanisms of the thicker shell, where the broken fibres are observed in the contact region of the indenter/composite and the consequent delaminations that result from this collapse.…”

“…In this case, there were increases of about 10% and 54.2% for the maximum load and displacement, respectively, while the stiffness decreased by about 47.1%. According to Coelho et al [42], regarding laminates with six layers, and comparing to cylindrical shells only with carbon fibres (6C), the maximum load is obtained for hybrid cylindrical shells involving carbon and Kevlar fibres, while the lowest value was obtained for those composed of carbon and glass fibres. In terms of stiffness, these authors observed that the highest value was obtained for cylindrical shells only with carbon fibres, while the lowest was obtained for hybrid shells of carbon and glass fibres.…”

“…Finally, studies developed by Arachchige et al [40,41] showed that the impact load increases with increasing stiffness, while the contact time decreases, and in relation to the impact velocity a direct relationship with the contact load was found. On the other hand, the hybridization effect was studied by Coelho et al [42] and a strong effect was observed in terms of static and impact responses. For example, composites cylindrical shells involving only carbon fibres had the highest stiffness and the lowest displacement at maximum load, but with the introduction of the glass fibres and Kevlar fibres these configurations had, respectively, the lowest stiffness and the highest maximum load and displacement.…”

Damage mechanisms in composite laminated shells subjected to multiple impacts at different points

“…These curves are representative of all the conditions tested, and are characterized by containing oscillations that can be attributed to the propagation of elastic waves, resulting from the specimen's vibrational response 33,34 . Furthermore, the curves show a profile that agrees with others reported in the literature for similar semi‐cylindrical composite shells 25–28,35,36 . In more detail, Figure 2 shows an increase in the impact force until it reaches a maximum value, peak force, followed by a somewhat abrupt decrease, depending on the point of impact.…”

“…33,34 Furthermore, the curves show a profile that agrees with others reported in the literature for similar semicylindrical composite shells. [25][26][27][28]35,36 In more detail, Figure 2 shows an increase in the impact force until it reaches a maximum value, peak force, followed by a somewhat abrupt decrease, depending on the point of impact. Conversely, the energy-time curves represented…”