The effects of fabric lamination angle and ply number on electromagnetic shielding effectiveness of weft knitted fabric-reinforced polypropylene composites

In this study, it was aimed to investigate the effects of fabric lamination angle and fabric ply number on electromagnetic shielding effectiveness (EMSE) of weft knitted fabric-reinforced polypropylene composites. Knitted fabric-reinforced composites are composed of aramid yarn, polypropylene yarn, and copper wire. Polypropylene is the matrix phase and the aramid yarn and copper wires are the reinforcement phase of the composite materials. It was achieved to form 1.5 to 3 mm thickness composites. The composites have nearly 20-50 dB electromagnetic shielding values. To form the knitted fabrics, 7G semiautomatic flat knitting machine was used. The composites were formed by a laboratory-type hot press. EMSE of composites were tested by using ASTM D 4935 coaxial test fixture in 27-3000 MHz frequency band. Lamination angle and ply number parameters were examined related to EMSE of structures. For this study, three different structures were knitted and named as plain knit, 1 x 1 rib knit, and half cardigan knit. To determine the effect of lamination angle of composites on electromagnetic shielding performance, the composites were produced in two different lamination angles as 0 degrees/90 degrees/0 degrees/90 degrees and 0 degrees/45 degrees/0 degrees/45 degrees. To determine the effect of fabric ply number of composites on electromagnetic shielding performance, the composites were produced in two and four plies. It was observed that the fabric ply number and lamination angle does not affect the EMSE of composite materials very much. It was determined that weft knitted reinforced composite structures have appropriate and high EMSE values for electromagnetic applications. This knitted fabric-reinforced polypropylene composites are flexible and suitable for other industrial applications as civil engineering, aerospace, etc.