Finite element simulation of the tensile properties of five-layer weft-knit spacer fabrics and investigation of insulation performance

Multilayer knitted fabrics are increasingly demanded in thermal protective clothing. However, achieving optimal balance between mechanical integrity and thermal insulation remains challenging. This study developed a five-layer weft-knitted fabric and evaluated its mechanical and thermal properties. A unit cell model was constructed in Rhino based on structural parameters and replicated to form the complete fabric architecture. Tensile behavior was simulated in ABAQUS under prescribed boundary conditions and displacement loads. Experimental tensile tests corroborated the numerical model, showing less than 8% error. Thermal insulation performance was assessed via active heating using embroidered conductive silver yarns under applied voltages of 10.0, 12.0, and 15.5 V. Steady-state thermal resistance tests were further carried out, and thermal resistance data of three-layer and five-layer fabrics were compared after thickness normalization. After normalization, the unit thickness thermal resistance of five-layer fabric was 6.20% higher than that of the three-layer counterpart. Infrared thermography revealed that the five-layer fabric exhibited more uniform temperature distribution and significantly delayed cooling compared to a three-layer control, demonstrating superior thermal insulation and enhanced structural stability.