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Engineering structures in aviation and marine experience complex loads and are often affected by repeated impact loads. The damage accumulated from deflection in the process of repeated impact will often seriously affect the safety of the structure. In this research, the low-velocity repeated impacts behavior of corrugated core structures was investigated through experimental methods. A series of low-velocity repeated impact tests were carried out to study impact resistance, taking into account the effects of varied impact sites and impact energy levels and the effects of different impact locations and different levels of impact energy. It is also observed from the test that the upper panel played a crucial role and experienced the coupling mode of the local indentations and global bending deformations during the repeated impacts tests. Three different failure modes were observed when changing the impact energies and impact locations. Moreover, the "pseudo-shakedown" phenomenon was also found when the energy of the impacts is 10 J on the short span. The present surveys provide a reliable method and insight into the dynamic response of the aluminum corrugated core structures when subjected to low-velocity repeated impacts, which could be a significant guideline for the investigation and lightweight design of shipping and aviation. [ABSTRACT FROM AUTHOR]

Corrugated core sandwich structures are fabricated with carbon fiber reinforced polymer (CFRP) face sheets and aluminum alloy cores. This lightweight design concept enables sandwich structures to maximize their specific bending stiffness/strength and improve their energy absorption capability. A combined experimental and numerical study is performed to investigate the effect of impactor shape on low-velocity impact behavior. Low-velocity impact tests are conducted to study the impact resistance when impacted by conical, hemispherical and flat impactors. A user subroutine VUMAT is developed to model the CFRP face sheet behavior, in which a progressive damage model based on the Hashin failure criteria and Yeh delamination failure criteria is implemented in ABAQUS/Explicit. Reasonably good agreement is achieved when comparing impact force, absorbed energy, and failure modes between experimental measurements and numerical predictions. These studies reveal that damage, consisting of fiber damage, matrix damage and delamination of the face sheets as well as buckling of core members, depends on the impactor shape, impact energy and impact location. The investigations provide some insight into the failure mechanisms in this hybrid sandwich structure under low-velocity impact loading, which could be used in the development of novel lightweight multifunctional structures. [ABSTRACT FROM AUTHOR]

Corrugated core sandwich structures are fabricated with carbon fiber reinforced polymer (CFRP) face sheets and aluminum alloy cores. This lightweight design concept enables sandwich structures to maximize the specific bending stiffness/strength and improve the energy absorption capability. The low velocity impact behavior of such structures is investigated by experimentally and numerically. A range of low velocity impact tests are conducted to study the impact resistance, considering the effects of impact energy, core thickness and impact site on the impact load, absorbed energy and failure modes. A user subroutine VUMAT is developed to model the composite face sheet behavior, in which a progressive damage model based on the Hashin failure criteria and Yeh delamination failure criteria is implemented in ABAQUS/Explicit. There is a generally good agreement between the experimental and predicted results in terms of impact force, absorbed energy, and failure modes of sandwich structures. These studies reveal that fiber damage, matrix damage and delamination of face sheets as well as buckling of core members occur under varied impact energies. The results provide insight into the low velocity impact behavior of such structures, and the knowledge of failure mechanisms could be useful for the development of novel lightweight multifunctional structures. [ABSTRACT FROM AUTHOR]

• Single and repeated impact behavior of carbon fiber corrugated sandwich structures is investigated. • The failure mode and bending bearing capacity of the structures after single or repeated impacts of different energy level is analyzed. • The influence of impact energy and impact frequency on the energy absorption capacity of carbon fiber corrugated sandwich panels has been studied. • An empirical formula of the relationship between residual strength factor, impact energy and number of impacts is established. Corrugated sandwich structures are fabricated with carbon fiber-reinforced polymer (CFRP) face sheets and cores. An experimental study was performed to investigate the response of this type of structure to impact loading; specifically, the impact force, energy absorption capacity, and failure mode were explored. The effects of the impact energy and the number of impacts on the corrugated sandwich structure damage were also studied. The failure modes and bending capacities of structures subjected to single or repeated impacts were analyzed. The bending capacities of the composite corrugated sandwich structures were related to the failure states of the panels. When a panel endured multiple impacts, its bending capacity significantly decreased; however, its energy absorption level first increased and then decreased. An empirical relationship between the residual strength factor, the impact energy, and the number of impacts was obtained. The findings of this study can serve as a reference for performance evaluations of marine composite structures subjected to combined impact and bending loading. [ABSTRACT FROM AUTHOR]

A novel composite double-arrow auxetic structure was designed and fabricated in this paper. The ballistic impact experiments were conducted using one stage gas gun to study the effects of the relative density on the impact responses and failure mechanism. The impact process of the projectile was recorded by a high-speed camera. The ballistic limit velocities, damage area and failure mechanism of composite double-arrow auxetic structure with different relative densities were compared and analyzed. The anti-penetration performances of composite double-arrow auxetic structure were evaluated and discussed based on the experimental results. In order to simulate and reveal the damage evolution process, the finite element model was used to simulate the ballistic impact process of composite double-arrow auxetic structure. The ballistic limit velocities and failure modes of the simulation results were compared with that of the experimental results. The comparison indicated that the simulated results were in agreement with the experimental results. • A novel composite double-arrow auxetic structure was designed and fabricated. • The ballistic impact experiments were conducted study the impact responses. • The anti-penetration performances of the structure were evaluated and discussed. • The finite element model was used to simulate the ballistic impact process. [ABSTRACT FROM AUTHOR]