Characterization and analysis of wrinkling behavior of glass warp knitted non-crimp fabrics based on double-dome draping geometry

The good formability of textile composite materials over complex mold geometries is one of the reasons to make their use expanding in various modern industries. However, different defects in these reinforcements could have occurred during the forming step in the manufacturing process. The defects are arising for many reasons; some are related to the fabric itself and others related to the draping parameters. Understanding the textile structure mechanics and draping behavior is essential to choose the proper reinforcement as well as to attain better simulation. Fabric wrinkles and local out-of-plane bucking of yarns were the fundamental defects in focus. The main objective of this part of the project was to experimentally investigate and compare the draping behavior of six commercially available glass fabrics from the same category of warp-knitted non-crimp fabrics (WKNCFs). The tested fabrics included two stitching patterns: tricot and chain. Also, they were relatively heavy with approximate mass per square meter. A double-dome punching test was performed to implement draping for each fabric; then, the defects were detected and characterized. Punching load-displacement curves were also recorded. In addition, a defect code was designated for the main defects to characterize forming defects at the meso-macroscopic scale. The structure and the number of fabric axes, stacking sequence, and stitching pattern all contribute to defect formation during draping. The studied configurations in this paper can help in studying the simulation of deformed technical fabric and provide a method to minimize and even eliminate the draping defects.