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A thin-walled sandwich structure filled with polyurethane is introduced. Based on the hyperelastic constitutive model of polyurethane, the energy absorption characteristics of the structure are studied and compared with single-layer and double-layer thin-walled steel circular tubes. Applying quasi-static load and dynamic load to the three structures, the deformation mode, energy absorption characteristic parameters, crushing force and stroke efficiency of the three structures are obtained. The results show that under quasi-static loading, the thin-walled circular tube filled with polyurethane produces axisymmetric deformation, and the average load and specific energy absorption are higher than the other two structures. Under dynamic loading, the stroke efficiency of thin-walled circular tube filled with polyurethane is small, but the average load and specific energy absorption are higher than the other two structures.

Bistable reeled composite shells (BRCS) have been widely used in deployable space structures due to advanced properties of light weight and large volume reduction. A finite element simulation and experimental validation to study the transition of BRCS between their two stable states are performed. In this article, multiscale representative volume element (RVE) modeling is used to compute the equivalent mechanical properties of carbon/epoxy plain woven fabrics that were utilized to construct the deployable composite laminates, followed by experimental verification. The deformation characteristics and strain energy distribution of the deployable composite shell (DCS) during snap through and coiling up are investigated using finite element analysis (FEA) and verified by strain‐gauge and digital image correlation (DIC) tests. The results show that the strain energy distribution in the snap through and coiling up of the carbon/epoxy plain woven BRCS with laminate stacking sequence of [+45/−45] is approximately symmetric. Additionally, an offset phenomena is observed during the coiling up of the BRCS in the finite element modeling. A parametric analysis is complemented to investigate effects of fiber angles on the deformation characteristics and strain energy distribution of the shell structures during snap through and coiling up. Highlights: Shell deformation during snap through and coiling up was investigated.DIC test was performed to capture the shell deformation.Strain energy distribution of the deployable composite shell was discussed.Offset phenomena are observed during the coiling up. [ABSTRACT FROM AUTHOR]

This paper mainly studies the dynamic response of composites with glass fiber as reinforcement and polypropylene resin as matrix under high-speed projectile penetration. The penetration effects of fiber unidirectional ply cross-ply and quasi-isotropic ply laminate were studied by using penetration velocities of 100–500 m/s. The effects of ply angle on ballistic limit velocity, target energy absorption rate and corresponding failure mode are analyzed. The correctness of the simulation model is verified by comparative experiments, and the ply angle of glass fiber reinforced polypropylene (GF/PP) composites is optimized. The results show that the energy absorption efficiency of the three kinds of laminated plates gradually decreases with the increase of the projectile incident velocity, and with the increase of the velocity, the absorption rate of the target plate gradually decreases tends to the same constant. The laminated plates with complex ply angles are simulated and analyzed, and the optimization results show that the ballistic limit velocity of fiber-reinforced composite laminates with ply angle of 30° is the highest. [ABSTRACT FROM AUTHOR]

A new kind of elastic metamaterial plate is designed to control the vibration and elastic wave propagation based on the band-gap mechanism. For the proposed elastic metamaterial plate, local resonant rods are periodically distributed between the two cover plates of the metamaterial plate structure. The dynamic stiffness matrix and the frequency response function of the structure under the time-harmonic excitation are obtained by the finite element and spectral element hybrid method (FE-SEHM). The experiment and simulation validations have been carried out. The effects of the material and structural parameters on the band-gap characteristics are analyzed. It is shown that the band-gaps can be computed more accurately and efficiently based on the FE-SEHM to avoid confusion between the pass-bands and band-gaps. Three band-gaps of the elastic metamaterial plate appear near the odd-order natural frequencies of the local resonant rods. Increasing the damping and mass of the local resonant rods results in the enlargement of the band-gap width, this enhances the capacity of the vibration reduction and sound isolation more effectively. [ABSTRACT FROM AUTHOR]

Abstract: The work is mainly focuses on the analysis of thermal gradients and its effect on thermal stresses in FGM (functional gradient material) grading‐strip made up of TiC‐Ni due to thermal heat with different rate: thermal shock, transient exponential and linear heat. In this paper, asymptotic analytical solution for exponential and linear heat will be investigated. Few models of material grading are considered: (a) models which depend on different volume content of TiC and (b) models with homogeneous layers. Thermal and mechanical properties of the material are assumed different along axis. It is assumed that Poisson's ratio and Young's modulus varies exponentially with the coordinate of the strip. The dependence on different material property idealizations is also investigated. As well for research maximum and minimal thermal stresses in paper compared laminated non‐FGM and FGM strip. The maximum tensile stress obtained for FGM case. At the same time compressive stresses near heated surface for two‐layered strip lager then for three‐layered and less or absent for FGM strip. Heating/cooling opposite edge to thermal shocked ones leads to increase/decrease compressive stress in metal phase part in FGM and layered strip. At the beginning of heat the differences in compressive stress for thermal shock and exponential heat could differ in ten times. Compressive stress in linear heat case increase from beginning and stay stable as maximum from three heat cases as long as edge heat up to maximum temperature. The results obtained in this research paper allow us to analyze the validity of this method and to understand principles of thermal behavior on FGM‐strip in a case of different conditions and different heat transfer rate. [ABSTRACT FROM AUTHOR]

Nanowires on elastic matrix are promising candidates for advanced mechanical/electrical coupling devices. In this paper, a piezoelectric nanowire resting on the elastic matrix is presented to study its electric buckling properties. Taking account of the surface effect, the critical voltage of the buckled nanowire is obtained theoretically. The analytical results show that the critical voltage is sensitive to the surface residual stress and surface piezoelectric constant. It is also revealed that the surface effect is more remarkable for higher buckling order. Moreover, the matrix modulus has strong influences on the electric buckling characteristics. This study may be useful to design and develop the mechanical properties of the nano structures and devices. [ABSTRACT FROM AUTHOR]

In this work, the functionally graded honeycomb structures with defects are investigated. It is shown how the patterns and locations of defects, as well as the density gradients, can affect the in-plane dynamic crushing behavior of honeycombs. Numerical results show that due to missing vertical cell walls, the deformation process for the transverse-vertical mixing defects is more complicated than that for pure vertical defects. For the honeycombs with negative density gradient, the I-shape deformation band is dominant during the dynamic crushing. However, the honeycombs with positive density gradient are crushed to densification with the combination of the first and second deformation bands. It is revealed that the ability of energy absorption could be improved by introducing the functional graded property. Moreover, under a high impact velocity, the gradient displays a high sensitivity on the energy-absorption capability of the honeycomb structures. At the early stage of crushing, the honeycomb structures with the positive density gradient behave the stronger capacity on energy absorption than those with the negative one. The energy-absorption curves for systems with positive and negative densities are symmetric about the homogeneous structures. As the compression proceeds, for the honeycombs with positive and negative density gradients, the trends of energy-absorptive abilities go into reverse. [ABSTRACT FROM PUBLISHER]