Validation of Explicit Digital Element Dynamic Relaxation Approach in Determining Micro-Geometry of 3-D Woven Fabrics

摘要

The digital element approach (DEA) has been employed to determine the micro-geometry of textile composite fabric preforms. In early research, a static DEA was used to simulate a 2-D weaving process in order to determine the fabric's micro-geometry (Wang and Sun 2001) (Zhou, Sun and Wang 2003). The major obstacle facing its application was the need for a huge amount of computer resource. In order to overcome this hurdle, a DEA static relaxation procedure was developed to determine fabric unit-cell micro-geometry (Miao, Zhou, et al. 2008). The static relaxation approach required less than 10% of the computer resource compared to the step-by-step static simulation. Recently, a more efficient DEA dynamic relaxation procedure was developed to determine the micro-geometry of various 2-D and 3-D fabrics. However, the accuracy of this DEA simulation to determine fabric micro-geometry has not yet been discussed in the open literature.The objective of this research is to analyze the effectiveness of the digital element dynamic relaxation approach in determining the 3-D fabric micro-geometry. The external dimension, surface patterns and interior micro-geometries of ten 3-D fabrics in ten different weaving patterns are investigated and compared to the DEA simulation results, qualitatively and quantitatively, in order to evaluate accuracy. Among the ten 3-D specimens, six consist of Nicalon CG and four of glass fibers. Fabric thicknesses range between 3mm to 10mm. Plain and twist yarn structures are both used. Fabrics cover a broad range of weaving styles.For each fabric specimen, the denier number of the yarn is measured with an analytical scale. Experimental results show a 2-10% discrepancy between the measured yarn denier number and the specified denier number. Based upon the measured denier number, the yarn cross-section area of each yarn is calculated and then employed in the numerical simulation. The thickness, the surface pattern, and the interior micro-geometries of all fabrics are derived using DEA simulation: all are compared to experimental observation. Accuracy of the DEA simulation is then discussed. The comparison validates the explicit digital element dynamic relaxation approach to determine the micro-geometry of 3-D woven fabrics.