•The 2-D lattice truss core sandwich panels are manufactured without bonding.•The mechanical behaviors depend on ρ‾ and the material properties of truss members.•Delamination is observed in compression, shear and bending tests, and no nodal failure modes.Composite sandwich structures with lattice truss cores are attracting more and more attention due to their superior specific strength/stiffness and multi-functional applications. In the present study, the carbon fiber reinforced polymer (CFRP) composite sandwich panels with 2-D lattice truss core are manufactured based on the hot-pressing method using unidirectional carbon/epoxy prepregs. The facesheets are interconnected with lattice truss members by means of that both ends of the lattice truss members are embedded into the facesheets, without the bonding procedure commonly adopted by sandwich panels. The mechanical properties of the 2-D lattice truss sandwich panels are investigated under out-of-plane compression, shear and three-point bending tests. Delamination of the facesheets is observed in shear and bending tests while node failure mode does not occur. The tests demonstrate that delamination of the facesheet is the primary failure mode of this sandwich structure other than the debonding between the facesheets and core for conventional sandwiches.

In this paper, low-velocity impact characteristics and residual tensile strength of carbon fiber composite lattice core sandwich structures are investigated by experimentally and numerically. Low-velocity impact tests and residual tensile strength tests are performed using an instrumented drop-weight machine (Instron 9250HV) and static test machine (Instron 5569), respectively. The FE (finite element) software, ABAQUS/Explicit is employed to simulate low-velocity impact characteristics and predict residual tensile strength of carbon fiber composite lattice core sandwich structures. These numerical investigations create a user-defined material subroutine (VUMAT) to enhance the damage simulation which includes Hashin and Yeh failure criteria. The impact contact force and the tensile strength are accurately estimated using the present method. From results of this paper, the degradation of residual tensile strength can be divided to three stages for different impact energies, and amplitudes of degradation are affected by stacking sequences.

Sandwich panel construction with carbon fiber-reinforced pyramidal lattice truss is attracting more and more attention due to its superior mechanical properties and multi-functional applications. Pyramidal lattice truss sandwich panels made from carbon fiber reinforced composites materials are manufactured by hot-pressing. The facesheets are interconnected with truss cores, the facesheets and truss cores are manufactured in one manufacturing process without bonding. The buckling and splitting of truss member is observed in the compressive and shear tests and no nodal failure is observed. The predicted results show that the mechanical behavior of the pyramidal lattice truss core sandwich panels depends on the relative density of core and the material properties of truss members.

3D sandwich structure with foam core reinforced by composite columns, a new concept of sandwich structure, is designed and manufactured. Five types of samples with different densities of composite columns (1, 1.5, 2, 2.5 and 4 columns/cm2) are fabricated, tested and analyzed under bending, out-of-plane compressive and shear loadings. The mechanical properties of compressive, bending and shear increase with increasing of the densities of composite columns. The failure modes were investigated under the optical microscope. The plasticity of the column–core sandwich structure subjected to bending and shear loads can be explained by the mechanism of the inclination and chain-like failure of composite columns.