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• Reinforcing the CFRP foam sandwich structure by orthogonal grid. • Testing the impact characteristics of each position at different energies. • Comparing the impact resistance of the sandwich panel at different positions. • Numerical simulation of the impact process for each position. • The proposed structure has the advantage of lightweight and high impact resistance. Orthogonal grid structures, which are widely used in engineering, are incorporated into the foam to form the grid reinforced core. However, the impact resistance of this type of sandwich structure varies with position. In this paper, the low-velocity impact performance of orthogonal grid reinforced CFRP-foam sandwich structure at different positions was investigated. The drop hammer low-velocity impact tests were conducted at 30 J, 50 J and 80 J energy for the intersection, rib, and center positions, respectively, and the impact resistance of the three positions was further compared with the impact data. The test results showed that the intersection and rib exhibited fiber fracture and delamination of CFRP face and grid, as well as foam crushing and cracking. The center position showed face perforation and foam crushing. At the same impact energy, the intersection position had the strongest impact resistance, with an initial stiffness about 18 % higher than that of the rib, and their peak load per unit mass was higher than that of CFRP-foam sandwich panels, and the center was the weakest. In addition, numerical simulations were performed which were in good agreement with the tests, and the damage processes at different stages were discussed. The lightweight, high impact resistant sandwich structure proposed can provide a reference for structural design. [ABSTRACT FROM AUTHOR]

In this study, compression properties of composite honeycomb sandwich panel and tube structures with S-shaped reinforced core was studied. The S-shaped reinforcements was machined from conventional honeycomb core. Quasi-static compression tests showed that the peak force and energy absorption of the proposed sandwich panels were enhanced by up to 85.28% and 31.41% respectively, in comparison to the carbon fiber/aluminum honeycomb sandwich panels. Based on the experimentally validated finite element model, the effects of number of S-shaped reinforcement structures, wall thickness and rotation direction were investigated for mechanical performance of the carbon fiber/aluminum honeycomb sandwich tubes under compression. Numerical results demonstrated that the S-shaped reinforcement structure could change the load transfer path effectively. The mechanical behavior and properties of the honeycomb core with S-shaped reinforcement were significantly influenced by changing the number and distribution of S-shaped reinforcements with different rotating directions. The homodromous structure caused shear damage, while the heterodromous structure showed more stability. • A honeycomb core with S-shaped reinforcements, which could effectively enhanced peak load and energy absorption, was proposed. [ABSTRACT FROM AUTHOR]

The full potential of carbon-fiber and aluminum-honeycomb sandwich panels and structures has been limited by the huge property mismatch between the high-stiffness carbon fiber and low-stiffness aluminum honeycomb. In this study, an orthogrid structure was added into the sandwich structure to raise the stiffness of soft honeycomb and therefore reduce the interfacial mismatch. The core then became an aluminum orthogrid structure filled with aluminum-honeycomb blocks. Three point bending tests were conducted to compare carbon fiber sandwiches with different types of core: (1) aluminum-honeycomb core; (2) aluminum-plate orthogrid core; and (3) aluminum-plate orthogrid core filled by aluminum-honeycomb blocks. The honeycomb filled orthogrid core sandwich was a bit heavier than the honeycomb or grid sandwich, but the critical load, specific strength and energy absorption ability were all improved. The results indicated that the honeycomb filled orthogrid core sandwich with carbon fiber face sheet could provide improved structural properties for thin walled engineering structures. [ABSTRACT FROM AUTHOR]