Viscoelastic behavior of warp-knitted spacer fabrics in iterative compression and decompression

In this study the viscoelastic behavior of warp-knitted spacer fabrics was investigated for compressional deformation. The fabric specimens were tested via loading and unloading time intervals under predetermined conditions. Following the upside tests, specimens were relaxed for 24 h to examine the recovery prior to completing the downside tests. The data obtained from the compression and decompression cycles were examined for stress relaxation and creep through stress–time plots. From the results it was observed that, despite the non-homogeneous structure of the spacer fabric, the specimens demonstrated exponentially changing behavior within the given time intervals. Since the response of fabrics to compression and decompression cycles can be expressed as a function of time, a mathematical approach was expressed in accordance with the time-dependent behavior of the fabrics regarding the monofilaments as bent beams. The responses of the fabrics to the experimental set up conditions were evaluated to determine the potential usage performances of the fabrics. Fabric thickness, number of monofilament yarns in the structure, and thickness of the monofilaments had the major effects on the performance of the fabrics. Future research could consider modeling studies to predict usage performance, and tailoring the fabrics before production.