On Low-Velocity Impact Properties of 3D Woven Integrated Double-Spacer Sandwich Composites

An experimental study on the low-velocity impact properties of 3D woven integrated double-spacer sandwich composite was carried out. The wet hand-lay-up molding process was explored to manufacture specimens of 3D woven integrated double-spacer sandwich composites. Low-velocity impact tests with different energies were then carried out to obtain the mechanical responses such as contact force, punch displacement and energy absorption rate. Three methods, i.e., visual inspection, ultrasonic C-scan non-destructive testing and industrial CT scanning, were used to determine the damage range and modes of 3D woven integrated double-spacer sandwich composites impacted with different energies. The damage range and modes were compared with the ones of intact specimens impacted with the same energy to explore the damage mechanism of 3D woven integrated double-spacer composites subjected to low-velocity impacts. The test results show that the maximum contact force, maximum punch displacement, residual deformation increase, and the depth of the dent and the damaged area of the top panel increase with the increase of impact energy, and the damage mode is gradually aggravated. Different from the conventional sandwich composites, the impact resistance of the core of the 3D woven integrated double-spacer sandwich composite is relatively low and the panels are the main structural elements to carry the impact load and absorb the impact energy.