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Composite sandwich panels with pyramidal lattice truss cores (CSPPLTCs) were manufactured employing waterjet-cutting technology and interlocking assembly. The effect of high-low temperature environments on the out-of-plane compressive and shear performance of the panels was studied using theoretical and experimental methods. In particular, the out-of-plane compressive stiffness, strength of sandwich panels with pyramidal lattice truss cores, their shear stiffness, and strength in high-low temperature environments were predicted using theoretical equations. The study found that in low-temperature environments, the movement of molecular chain segments in the epoxy is hindered, futhermore, the mismatched thermal expansivity of carbon fiber and epoxy resin leads to the improvement of interface bonding performance, thus improving the out-of-plane compressive and shear performance of CSPPLTCs; in high temperature environments, the movement of molecular chain segments in the epoxy gets more active and tends to move freely, so the resin turns into a flexible state with high elasticity from the stiff glass state, which finally causes a deterioration in out-of-plane compressive and shear performance of CSPPLTCs. According to observations, the failure mode depends on temperature environments. Brittle fracture and crushing failure happen in the composite struts at low temperature; plastic microbuckling may happen in the composite struts at high temperature. [ABSTRACT FROM AUTHOR]

This work investigated the effect of graphene nanoplatelets (GNPs) on the water absorption and impact resistance of fibre-reinforced metal laminates (FMLs) under hygrothermal and salt spray environments. Containing GNPs of 0.1, 0.3, 0.5 and 1.0 wt%, the resulting nanocomposite FMLs were investigated for 28 days of aging in the environments. The salt-spray environment was found to pose a more serious effect on FMLs than the hygrothermal environment. The addition of GNPs at 0.3 wt% effectively reduced the water absorption of FMLs by 57.6% whilst improving their impact resistance by 150.6% in comparison with pure FML in the case of treatment by the salt-spray environment. The water absorption reduction is caused by GNPs creating a tortuous path for diffusion of water molecules and restricting the intermolecular motion of the epoxy molecules. The impact resistance improvement can be attributed to GNPs improving the modulus and crack-resistance of the epoxy matrix and thus the interfacial bonding of FMLs. [ABSTRACT FROM AUTHOR]