The aim of this study is to review three-dimensional (3D) braided fabrics and, in particular, to provide a critical review of the development of 3D braided preform structures and techniques. 3D braided preforms are classified based on various parameters depending on the yarn sets, yarn orientation and intertwining, micro-meso unit cells and macro geometry. Biaxial and triaxial two-dimensional (2D) braided fabrics have been widely used as simple- and complex-shaped structural composite parts in various technical areas. However, 2D braided fabric has size and thickness limitations. 3D braided fabrics have multiple layers and no delamination due to intertwine-type out-of-plane interlacement. However, the 3D braided fabrics have low transverse properties and they also have size and thickness limitations. On the other hand, various unit cell base models on 3D braiding were developed to analyze the properties of 3D braided structures. Most of the unit cell base models include micromechanics and numerical techniques. Multiaxis 3D braided fabrics have multiple layers and no delamination. The in-plane properties of multiaxis 3D braided fabrics may be enhanced due to the ±bias yarn layers. However, the multiaxis 3D braiding technique is at an early stage of development and needs to be fully automated.

The aim of this study is to review three-dimensional (3D) fabrics and a critical review is especially provided on the development of multiaxis 3D woven preform structures and techniques. 3D preforms are classified based on various parameters depending on the fiber sets, fiber orientation and interlacements, and micro-meso unit cells and macro geometry. Biaxial and triaxial two-dimensional (2D) fabrics have been widely used as structural composite parts in various technical areas. However, they suffer delamination between their layers due to the lack of fibers. 3D woven fabrics have multiple layers and no delamination due to the presence of Z-fibers. However, the 3D woven fabrics have low in-plane properties. Multiaxis 3D knitted fabrics have no delamination and their in-plane properties are enhanced due to the AEbias yarn layers. However, they have limitations regarding multiple layering and layer sequences. Multiaxis 3D woven fabrics have multiple layers and no delamination due to Z-fibers and in-plane properties enhanced due to the AEbias yarn layers. Also, the layer sequence can be arranged based on end-use requirements. However, the multiaxis 3D weaving technique is at an early stage of development and needs to be fully automated. This will be a future technological challenge in the area of multiaxis 3D weaving.

In this study, multiaxis 3D woven preform was developed with five yarn sets: + bias, -bias, warp, filling, and z-yarns. The orientation of the yarns on the five axis have improved the mechanical properties of the preform. The yarns of the preforms, which were made of polyacrylonitrile (PAN)-based carbon fibers, were consolidated with an epoxy resin. These preforms were tested and compared with the 3D orthogonal woven carbon composites. It was found that in-plane shear strength and modulus of multiaxis 3D woven composite were higher than that of the 3D orthogonal woven composite. However the bending strength, bending modulus, and the interlaminar shear strength of the multiaxis 3D woven composite were slightly lower than that of the 3D orthogonal woven composite because of the orientations of +/-bias yarns on both surfaces of the multiaxis 3D woven structure. The failures of both woven samples were also analyzed for the assessment of their mechanical behaviors. The unit cell of the multiaxis 3D woven preform was described. Depending on the unit cell geometry, some relationships were developed to predict the volume fraction of each yarn set in the preform and these predicted results were also compared with the measured values.

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.

In this study, the impact resistance of two-dimensional (2D) fabrics and three-dimensional (3D) preforms is explained. These fabrics and preforms include 2D and 3D woven and knitted flat and circular fabrics. Various types of soft/layered structures as well as rigid composite are outlined with some design examples for ballistic and stab threats. The recent developments in nanotubes/nanofibers and shear-thickening fluids (STF) for ballistic fabrics are reviewed. The ballistic properties of single- and multi-layered fabrics are discussed. Their impact mechanism is explained for both soft vest and rigid armor applications. Analytical modeling and computational techniques for the estimation of ballistic properties are outlined. It is concluded that the ballistic/stab properties of fiber-reinforced soft and rigid composites can be enhanced by using high-strength fibers and tough matrices as well as specialized nanomaterials. Ballistic/stab resistance properties were also improved by the development of special fabric architectures. All these design factors are of primary importance for achieving flexible and lightweight ballistic structures with a high ballistic limit.