The aim of this study was to understand the energy absorption mechanism and failure modes of newly developed multidirectionally-stitched structures. Para-aramid woven fabric was used. The structures were in unstitched and stitched forms. Nylon 6.6 yarn was used to stitch the structure in one, two and four directions whereas Kevlar^® 129 yarn was used to make only the four-directionally-stitched structures. The yarn pull-out fixture was developed and the yarn pull-out test was performed on single woven fabric and stitched structures. Ballistic tests were performed on the structures using 9 mm full metal jacketed projectiles with a speed of 300 to 400 m/s. If the applied kinetic energy level is under the yarn breaking extension, crimp in the orthogonal yarns at the fabric structure is firstly removed, and thereafter yarn pull-out takes place in the structure plane, and later stage fabric deformation occurs in the out-of-plane direction of the structure. This phenomenon continues from the outside to the inside layers. If the applied kinetic energy level is above the yarn breaking extension, firstly partial and total filament breakages and subsequently crimp removal and yarn pull out stages occur. These phenomena take place as multiple yarn failure in the outer layers and mostly crimp removal and yarn pull-out towards the inside layers occur. In both cases, fabric and structure bending were ignored. The energy absorption level of the stitched structures was slightly higher than that of the unstitched structures due to the fact that some of the energy was absorbed to delaminate the interlayer, which was locked by the stitching yarns. Also, the conical depth in the stitched structure was low compared with that of the unstitched structure.

The aim of this study was to understand the pull-out properties of para-aramid woven fabrics. Para-aramid Twaron CT714 and CT716 woven fabrics were used to conduct the pull-out tests. Twaron CT714 and CT716 woven fabrics have low and high fabric densities, respectively. A previously developed yarn pull-out fixture was improved to test various fabric sample dimensions. Data generated from the single and multiple yarn pull-out tests using various dimensions of CT714 and CT716 woven fabrics included fabric pull-out forces, yarn crimp extensions in the fabrics and fabric displacements. Yarn pull-out forces depend on fabric density, fabric sample dimensions and number of pulled ends in the fabric. Results showed that the multiple yarn pull-out force was higher than that of the single yarn pull-out test. Single and multiple yarn pull-out forces in Twaron CT716 (tight fabric) were higher than those of Twaron CT714 (loose fabric). Yarn crimp extension in Twaron CT714 and CT716 fabrics depends on crimp ratios in the warp and weft directions in the fabrics and on fabric density. High crimp ratio fabrics showed high yarn crimp extension in the fabric compared to that of low crimp ratio fabrics. Wide and long fabric samples also showed high yarn crimp extension compared to that of the narrow and short fabric samples. Fabric displacement in Twaron CT714 and CT718 fabrics depends on fabric sample dimensions and the number of pulled yarns. Wide and long fabric samples showed high fabric displacement compared to that of the narrow and short fabric samples. Fabric displacement resulting from the multiple yarn pull-out test was also higher than that of the single yarn pull-out test. Future research will concentrate on the development of the analytical relations between pull-out and yarn-fabric structural parameters which could result in a ballistically better fabric structure for use in soft ballistic applications.

Webbings are used in parachute assemblies as reinforcing units for the strength they provide. The strength of these seams is an important characteristic which has a substantial influence on the mechanical property of the parachute assemblies. It is well established that factors such as fabric width, folding length of joint, seam design and seam type will all have an impact on seam strength. In this work, the effect of these factors on seam strength was studied using both Taguchi's design of experiment (TDOE) as well as an artificial neural network (ANN). In TDOE, two levels were chosen for the factors mentioned above. An L8 design was adopted and an orthogonal array was generated. The contribution of each factor to seam strength was analyzed using analysis of variance (ANOVA) and signal to noise ratio methods. From the analysis it was found that the fabric width, folding length of joint and interaction between the folding length of joint and the seam design affected seam strength significantly. Further, using TDOE, an optimal configuration of levels of factors was found. In order to contrast and compare the results from TDOE, an ANN was also used to predict seam strength using the above mentioned factors as inputs. The prediction from TDOE and ANN methodologies were compared with physical seam strength. It was established from these comparisons, in which the root mean square error was used as an accuracy measure, that the predictions by ANN were better in accuracy than those predicted by TDOE.

Seam slippage, which occurs frequently in furniture upholstery fabrics on the parallel sewing line, even though it is undesirable, results in partial or full distortion of fabric appearance. The purpose of this study is to reduce the seam slippage in upholstery chenille fabrics, which are widely used in furniture production. This is the preliminary study, in which the effects of sewing direction and the number of interlaced chenille yarns over warp yarns on seam slippage were investigated for the first time. Aside from the effects of fiber content, sewing stitch step, weft densities of fabrics, sewing direction according to the weft and warp and the number of interlaced chenille yarns over warp yarns on seam slippage were studied with the use of multifactor experiment. On the basis of these experiments, effects and impact factors of the aforementioned parameters on seam slippage were shown with the use of mathematical models.

Carbon nanotubes (MWCNTs) were synthesized in situ on para-aramid fabrics (gCPO) via a low-temperature (450 °C) chemical vapor deposition (CVD) process to enhance interfacial pull-out, frictional, and fracture toughness characteristics. FESEM analysis confirmed CNT coverage on fiber surfaces, while FTIR, Raman, and XRD results indicated limited structural modification without significant polymer degradation. The CNT-functionalized fabrics exhibited a 66.19% increase in maximum pull-out force, 55.32% improvement in interlacement rupture strength, and a three-fold rise in intra-yarn shear resistance compared with control fabrics (KPO). The static and kinetic friction coefficients increased by 26.67% and 16.67%, respectively, due to CNT-induced surface roughness, enhancing inter-fiber load transfer and reducing slippage. Single-yarn pull-out tests revealed notable gains in energy dissipation and fracture toughness (up to 1769 J/m²), whereas multi-yarn pull-out performance decreased due to excessive friction surpassing filament strength. The study demonstrates that low-temperature MWCNT growth enables effective interfacial reinforcement of soft para-aramid fabrics, establishing a novel framework for meso-scale mechanical screening of flexible nano-ballistic composites.