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This study deals with numerical and experimental free vibration analysis of through-the-thickness cylindrical polymer pin-reinforced foam core sandwich composite panels of two different core thicknesses. Four different pin-reinforcement configurations with varying pin diameters and pin center distances were used. First five non-zero eigenfrequencies were retrieved along with their eigenmodes in the numerical analysis. Experimental modal analysis was done for the validation of the numerical analysis. The results revealed that the pin-configuration with the densest pin allocation and the biggest pin diameter provided the highest natural frequencies, and the non-reinforced composites had the lowest natural frequencies. The increase in the pin diameter had a slightly more pronounced effect on the increase of the eigenfrequencies than the increase in the pin's densities. This work also demonstrated the impact of the core thickness on the natural frequencies. [ABSTRACT FROM AUTHOR]

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A transient-dynamics model based on the approximate Riemann algorithm is proposed for the failure analysis of a frangible composite canister cover. The frangible cover, manufactured with a traditional manual lay-up method, is designed to conduct a simulated missile launch test using a specially developed test device. Deformation of the cover’s centre is determined using a transient-dynamics finite element model; failure pressure for the frangible cover is obtained based on a failure criterion and compared with simulated experimental results. Weak-zone position of the frangible cover has a significant effect on failure pressure compared to that of deformation of the cover’s centre. With the same structure of the weak-zone, an increase in its height can first raise and then reduce the level of failure pressure of the frangible cover. Close agreements between the experimental and numerical results are observed. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) woven composites have been widely used in structural components due to their excellent mechanical and near-net-shape properties. However, for some special applications, it is expected that 3D woven composites can be damaged at designated locations under a specific load. In this research work, a new kind of defect-prefabricated 3D woven composites (DP3DWCs) are designed, where defects are prefabricated by cutting weft or warp yarns in defect-free 3D woven composites (DF3DWCs). The tensile mechanical properties of the DF3DWCs and the DP3DWCs are investigated experimentally and numerically. The mesoscopic geometry models of the DF3DWCs and the DP3DWCs were established by multi-objective searching algorithm. The progressive damage models were established using the 3D Hashin criteria and the von Mises failure criterion. Numerical results agree well with the experimental data. The influence of the number of defect layers on the mechanical properties was also discussed. The obtained results indicate that the defects have little effect on the elastic modulus, while tensile strengths decrease linearly with the increase of the number of defect layers. Failure mechanisms of yarns and matrix in the non-defective and defective materials were studied, and the volume fraction of elements of each failure mode was computed and analysed. [ABSTRACT FROM AUTHOR]

Based on the far field function of electric field, a new glass carbon fiber gradient-stitched structure is proposed and designed in the paper. In the frequency range of 8–28 GHz, the electric field distribution of transverse electric and magnetic field (TEM) waves incident obliquely on the surface of the structure by optimizing the glass fiber fabric units. It is confirmed that the surface has the function of suppressing electromagnetic wave reflection. The electrical performance simulation and testing results of the structure show that the radar cross section (RCS) is reduced by 90% in the frequency range of 12.3–26.5 GHz. In addition, a multi-scale analysis model is established to quickly predict the tensile modulus and strength of the composite material. The strength and modulus reached 26.9 GPa and 403 MPa, respectively. The simulating and testing results of mechanical properties are in good agreement. [ABSTRACT FROM AUTHOR]