Investigation into the Role of Z-Fiber Orientation in Low-Velocity Impact Behavior of Sandwich-Structured Composite: Numerical and Experimental Analysis

Sandwich composites reinforced with weft-knitted spacer fabrics (WKSF) have a high potential for use in low-velocity impact applications due to the presence of Z-fibers. The present research fabricated sandwich composites using C-glass weft-knitted spacer fabrics and epoxy resin. Three different architectures, i.e., 1 x 1-Rib gaiting, 3 x 3-Rib gaiting, and 5 x 5-Rib, were used to achieve different orientations of Z-fibers. Low-velocity impact test was carried out on the prepared samples. Also, the impact behavior of the sandwich composite was simulated using ABAQUS standard/explicit. The experimental and numerical results show that Z-fibers affect the low-velocity impact behavior of sandwich composites. Based on experiments, the lower maximum reduced acceleration of the impactor and higher contact duration in 3 x 3 Rib-gating means that this specimen has more impact resistance. The indentation percentages of 1 x 1-Rib gaiting, 3 x 3-Rib gaiting, and 5 x 5-Rib gaiting samples were 37%, 34%, and 91%, respectively. In addition, considering the thickness of composites, the experimental indentation of 3 x 3 Rib-gating is lower than other samples which is confirmed by the numerical displacement of the impactor. Numerical analysis showed that the elastic modulus of Z-fibers, its position, and boundary conditions affected stress distribution. The discontinuity among Z-fibers prevents the transfer of stress from the impact area to the outside of this area. Generally, composites reinforced with 3 x 3-Rib gaiting structures show the highest resistance to impact stiffness.