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It is a challenging task to advance the excellent strength and structural performance of sandwich structures, while continuing to reduce the weight and cost parameters. Thousands of researchers have studied and developed the core structural innovation with periodical achievements. This review paper concentrates on the core structural trends and impact response of sandwich panels, which highlights the novel design concepts and impact failure modes. Three kinds of core structures have been classified, which are foam-core, two- and three-dimensional periodic cores. It is shown that the core structure of sandwich panels plays a vital role in structural performance and applications. Three common types of loading conditions have been considered, i.e. compression, projectile impact and three-point bending. Examples of novel core structures are further studied and summarised under corresponding impact loadings. Recent applications of sandwich structures are briefly concentrated on aerospace, automotive, marine and civil engineering areas. Furthermore, future research and development prospect of sandwich structures are suggested and predicted. [ABSTRACT FROM AUTHOR]

In order to investigate the impact resistance of the Nomex honeycomb sandwich structures skinned with thin fibre reinforced woven fabric composites, both drop-weight experimental work and meso-mechanical finite element modelling were conducted and the corresponding output was compared. Drop-weight impact tests with different impact parameters, including impact energy, impactor mass and facesheets, were carried out on Nomex honeycomb-cored sandwich structures. It was found that the impact resistance and the penetration depth of the Nomex honeycomb sandwich structures were significantly influenced by the impact energy. However, for impact energies that cause full perforation, the impact resistance is characterized with almost the same initial stiffness and peak force. The impactor mass has little influence on the impact response and the perforation force is primarily dependent on the thickness of the facesheet, which generally varies linearly with it. In the numerical simulation, a comprehensive finite element model was developed which considers all the constituent materials of the Nomex honeycomb, i.e. aramid paper, phenolic resin, and the micro-structure of the honeycomb wall. The model was validated against the corresponding experimental results and then further applied to study the effects of various impact angles on the response of the honeycomb. It was found that both the impact resistance and the perforation depth are significantly influenced by the impact angle. The former increases with the obliquity, while the latter decreases with it. The orientation of the Nomex core has little effect on the impact response, while the angle between the impact direction and the fibre direction of the facesheets has a great influence on the impact response. [ABSTRACT FROM AUTHOR]

The quasi-static flexural and impact performance, up to projectile impact velocities of about 270 m s, of fibre metal laminates (FMLs), which consist of relatively thin, alternately stacked, layers of an aluminium alloy and a thermoset glass fibre epoxy composite, have been investigated. The effects of varying (a) the yield strength, tensile strength and ductility of the aluminium alloy layer, (b) the surface treatment used for the aluminium alloy layers and (c) the number of layers present in the FML have been studied. It was found that increasing the strength of the aluminium alloy increases the quasi-static flexural strength of the FML, providing that good adhesion is achieved between the metal and the composite layers. Further, increasing the number of alternating layers of the aluminium alloy and fibre composite also somewhat increases the quasi-static flexural properties of the FML. In contrast, increasing the strength of the aluminium alloy had relatively little effect on the impact perforation resistance of the FML, but increasing the number of alternating layers of aluminium alloy and fibre composite did significantly increase the impact perforation resistance of the FML. The degree of adhesion achieved between the layers had only a negligible influence on the impact perforation resistance. [ABSTRACT FROM AUTHOR]

Although rubberized concrete is widely accepted as an eco-friendly building material, its engineering applications are far limited due to its relatively low strength. To address this deficiency, the current study examines the effect of enhancing the strength of rubberized concrete through incorporating basalt fibers (BF) and water-based epoxy resin (ER) at varying proportions. In this study, both experimental testing and numerical simulations were conducted to investigate the mechanical, impact, and abrasion resistance properties of BF-ER composite enhanced rubberized concrete (BERC) using 12 different mix ratios. The evolution of damage in BERC was investigated, and the reinforcing mechanism of the fiber-polymer composite was elucidated through micro-morphology and pore structure analysis. The results indicate that the compressive strength and impact resistance of rubberized concrete are significantly improved due to inclusion of BF-ER, with the former achieving up to 60 % higher than normal rubberized concrete, while the latter attains improvement of 100 %. Due to the energy-absorbing behavior of rubber particles and the enhanced bonding effect provided by fiber-polymer, BERC exhibited a ductile failure mode, characterized by development of more complex cracks. Inclusion of fiber polymer resin has strengthened the weak interfacial transition zone (ITZ) between rubber particles and cement paste, albeit at the cost of increased porosity caused by the multiple interfaces of BF. From the current study, the optimal dosages of BF and ER are determined to be 2 kg/m3 and 4 kg/m3, respectively. The research results have provided useful insights on the application of rubberized concrete in critical engineering structures that require impact and abrasion resistance. • Mechanical properties and microstructures of BF and ER reinforced rubberized concrete were studied. • The influences of epoxy resin content on abrasion resistance of the BERC. • Effects of basalt fiber on compressive behavior and failure mode of rubberized concrete. • The basalt fiber and epoxy resin could be used in rubberized concrete to improve impact resistance. [ABSTRACT FROM AUTHOR]