F MADANI - PhD student, Department of Textile Engineering, Isfahan University of Technology, Isfahan, Iran
M AZADIAN - PhD student, Department of Textile Engineering, Isfahan University of Technology, Isfahan, Iran
M.M Shokrieh, - Professor, Composites Research Laboratory, Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Technology, Narmak, Tehran, Iran
H HASANI - Associate Professor, Department of Textile Engineering, Isfahan University of Technology, Isfahan, Iran

The composite structures damaged when exposed to low velocity impacts that this damages decrease the mechanical properties of structures. In this study the residual strength of the 3D integrated weft-knitted sandwich composites (3DIW-KSCs) with different cross-section includes: 20 mm height triangular, single decker rectangular with 20 and 30 mm of height and 32 mm height double decker rectangular investigated under three points bending test in two ways(compression and tensile) and compared with 20 mm foam core sandwich composite. Firstly the samples impacted by drop weight impact tests in 16 j. in this energy level the visible damage occurred on impacted face of samples while the bottom face of all samples were intact. The damaged samples were tested by the three points bending test with ASTM C393. For determining the residual tensile and compression strength after impact of samples, the intact face and damaged face of samples placed under load bar respectively. The results showed that the bending residual strength after impact (BRSAI) of foam core sandwich composite more than the other samples expect of triangular 3DIW-KSC in compression and tensile. The BRSAI decreased in compression and tensile ways by increasing of height in single decker rectangular samples. The lowest BRSAI belonged to the single decker 30 mm and double decker rectangular samples. The triangular 3DIW-KSC had the highest BRSAI in tensile and compression ways as the BRSAI of this sample in tensile was 96 percent that this phenomenal behavior related to Angle position (± 45°) of connecting layers to each other’s. Generally the BRSAI of samples in tensile were more than the compression way.

3DIW-KSC, drop weight impact test, BRSAI