Braided reinforced composites

Naik RA. Failure analysis of woven and braided fabric reinforced composites. J Compos Mater 1995 29 2334-63. 

The surface is molten during forming, so the surface finish tends to have a fibrous finish. Fiber separation could occur for extremely complex parts. The use of braided woven fabrics and continuous fiber mat reinforcements practically eliminates separation (Chapter 7). Discontinuous fiber reinforced composites, such as those made by the slurry process, can be molded into complex shapes without separation. 

Stmctures such as braided, tufted, felt, film, foam, laminated, bonded, stitched-through, net, embroidery, quilt and laced stmctures can also be formed. Textile composites and fibre-reinforced composites are another form of textile stmctures, consisting partly of textile materials (Corbman, 1983). 

With respect to the laminates as a structural material, regardless of the type of reinforcement, there are known some behaviour characteristics during the mechanical loading of laminates. Composites with woven reinforcement demonstrate (Dauda et al. 2009) a linear relationship between stress and deformation. Whereas the reinforcement of laminates in the form braided reinforcement show a non-linear dependence is determined by an angle of orientation of the fibre bundles with respect to the axis of symmetry. The increase in flexural strength and modulus values affects the volume fraction of fibres in the composite volume, and the surface density of the strengthening. 

So far, the bulk of literature has concentrated on characterizing the mechanical properties of both thermosetting- - - and thermoplastic-based - knitted composite materials. The modeling of the mechanical properties (mainly stiffness and tensile) has also been popular. However, limited literature exists on the forming property characteristics of knitted fabric-reinforced thermoplastics - and their processing properties are still poorly understood. In fact, most of the literature on forming properties deals with unidirectional, - mostly woven and, to a lesser extent, braided reinforcements, rather than knitted reinforcements. 

Fibrous Composites. These composites consist of fibers in a matrix. The fibers may be short or discontinuous and randomly arranged continuous filaments arranged parallel to each other in the form of woven rovings (coUections of bundles of continuous filaments) or braided (8). In the case of chopped strand mat the random arrangement is planar. In whisker (needle-shaped crystals or filaments of carbon and ceramics) reinforced materials the arrangement is usually three-dimensional and the resulting composites are macroscopically homogeneous. 

Use of fibers as reinforcements to make composites is, of course, well established. These are structural applications where, because of the characteristically long length of fibers, they are incorporated in a continuous medium, called the matrix. We describe some of these applications in subsequent chapters in more detail. Yet another common use of fibers of various kinds is in making ropes. In prehistoric times, ropes were made of braided leather strips and vines. Later, vegetable fibers such as jute, hemp, etc., were used to make ropes. More recently, ropes have been made of synthetic pol3nmers and metallic fibers. Ropes can be made by a variety of construction methods twisted, braided, plaited, parallel core and fiber, and wire rope. 

ZSIGMOND B., HALASZ L., CZVIKOVSZKY T., EB processing of carbon fiber reinforced braided composites, Radiat. Phys. Chem., 67, 441 - 445, 2003. 

In this section we select the most important criteria of correspondence of a model to reality. Then, we overview both the peculiarities of textile reinforcement that must be accounted in an ideal damage model and the requirements to the solid models asserted by various FE approaches. Meso-scale 3D FE models available in literature are classified according to the selected geometric features. Models of 2D braided composites are included in the overview to give a wider perspective. In many aspects, challenges for modelling 2D braided and 2D woven yam architectures are exactly the same. 

Due to the complex nature of the textile reinforcement since air can become entrapped in the interstices of the fabric structure. This can be particularly evident when coarse yams (or tows) are used or in complex three-dimensional (3-D) stmctures, e.g. braided or woven, and may be most prevalent at the tool/composite interface. 

Manufacturers of composite structures have traditionally used prepreg tape to manufacture structural components. Fibres are initially combined into unidirectional tows (bundles) of fibres combined into fabrics, e.g. by weaving or knitting. The vast majority of the tows employed in woven, braided or knitted reinforcements comprise low twist or untwisted continuous filament yams. Three-dimensional technical textiles can be produced by weaving [5], knitting [6] and braiding [7] or as non-crimp fabrics. 

The fatigue behaviour is an important parameter to investigate for composites with a textile reinforcement structure. Warp knitted, braided and woven reinforcements will find increasing attention in future. 

LAS glass-ceramic matrix composite reinforced by 3-D braid Nicalon yarns and SiC monofdaments in (he axial direction. Tensile strength 656 MPa Aerospace [2]... 

The 21st century has already seen rapid advances in the field of textile-based composites. In addition to traditional two-dimensional woven fabrics, multiaxial non-crimp fabrics are now very widely used, with a rapidly growing number of applications for braided composites. Developments in three-dimensional weaving, combining through-thickness reinforcement with excellent in-plane properties, provide new design solutions for situations where delamination must be avoided. Textile reinforcement is thus providing major new areas of opportunity for composite materials worldwide. 

In addition to being available as continuous filaments and staple fibers in mats, fiberglass textiles are also available as biaxial, triaxial, knitted and three dimensional braided patterns. Many different resin matrices are in use but the emphasis in this chapter will be on unsaturated polyester and epoxy resins. While the strength and stiffness are controlled primarily by the reinforcements, the resinous matrix contributes to thermal conductivity and flexibility. The ultimate properties of these composites are based on a harmonious contribution of both the continuous and discontinuous phases. 

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