Monofilament woven fabrics

The reinforcing ply of laminates may be a woven fabric scrim, a nonwoven web of polymer monofilaments, or a mat of fibers. One of the most common reinforcements in use is also one of the oldest, ordinary cellulose fiber paper. 

Other reinforcements that may be used in the substrate layers of decorative laminates and throughout the stmcture of industrial laminates are woven fabrics of glass or canvas and nonwoven fabrics of various polymeric monofilaments such as polyester, nylon, or carbon fibers. Woven and nonwoven fabrics tend to be much stronger than paper and have much more uniform strength throughout the x—y plane. They greatly enhance properties of laminates such as impact and tear strength. 

Woven fabrics are usually made with natural or synthetic fibers from three different types of yams monofilament, multifilament, and spun staple, as shown in Figure 22.65. Performances of these three types of yams are shown in Table 22.12. 

Types E and S glass are available as monofilaments, as roving (a series of parallel, untwisted glass strands, each strand composed of glass filaments), or as woven fabrics. These products are highly developed and are available with special finishes to ensure compatibility with various matrix resins. 

In the case of nonwoven fabrics, a reduction in pore size is achieved by compressing the fibres into a more dense structure (loads up to 300decaNm" may be necessary) and, by selection of the appropriate conditions, a more durable (Fig. 3.31) surface can also be obtained through partial fusion of the surface fibres. With woven fabrics, on the other hand, some deformation of the yams may be necessary to achieve the optimum filtration properties. This is particularly graphic in the case of fabrics woven from monofilament yams, as shown in Fig. 3.32 and Fig. 3.33. 

Woven geotextiles. A woven fabric consists of two sets of orthogonally interlaced filaments or staple-fibre yams. The weave design or pattern is determined by the manner in which yams or filaments are interlaced. Filaments or yams placed in the longitudinal and transverse directions are known as warp and weft, respectively. Monofilament and slit woven geotextiles are anticipated to be thinner in comparison to multifilament, spun, and fibrillated woven geotextiles. 

Figure 2. SEM micrographs of a woven fabric made of PET monofilaments (left) and of a woven fabric made of polyamide multifilament yarn (right).

Employing a vacuum-bag technique, atmospheric pressure can be used to hold the skin to the honeycomb during cure. A sandwich of the new skin, a film adhesive and polyester non-woven monofilament fabric (3M-AF 3306 is satisfactory) is placed on the honeycomb. In this case, a film adhesive layer of 0.085 Ib/ft or two layers of 0.06 Ib/ft should be used. The thickness of AF 3306 should not exceed 0.003 in. The vacuum bag is sealed around the damaged area and evacuated, the non-woven fabric providing a conduit for the air pumped out. Elevated pressure may also be required to prevent honeycomb/skin disbond adjacent to the repair area. Complete rebuilding can be done in this way." ... 

Monofilament and multifilament woven fabrics are generally made from PET, the use of monofilament giving the better permeabihty, whereas multifilament is used for higher strength reinforcement. SHt film, flat-tape fabrics are usually PP materials, which are quite strong but they form a fabric that has relatively poor permeability. Alternatively, fabrics made with fibriUated-tape yarns have better permeability and more uniform interstice openings than flat-tape products. 

Woven fabrics, as their name says, are woven from yams or slit film monofilaments using different weaving methods. For slit film monofilament production foils are first extmded and stretched, and then cut into small monofilaments. 

One of four basic yarn types, shown in Figure 2.2, is normally employed in the production of woven fabrics monofilaments, multifilaments, staple spun yams and fibrillated tape yams (a helpful summary of trade names is given by Purchas and Sutherland, 2002). 

Other applications are in monofilaments, nonwovens, films, engineering thermoplastics, and molded goods. Paper forming fabrics made with PTT monofilaments have been patented (53) for use in papermaking machines because PTT combines the chemical resistance of a polyester and the resiliency of the less chemical resistant nylon. PTT non-woven fabric shows better dimensional... 

Even though fibres of the above synthetic materials can be woven multifilament or monofilament, there is a trend towards the use of monofilament filter fabrics. This is so mainly because in years past it was very difficult to weave monofilaments in the fine, low-micron retention areas. Today, monofilament filter fabrics can be woven twilled down to 6 pm and plain reverse Dutch down to 14 pm. Further finishing (shrinking and calendering) can bring the particle removal rating down to the 1 pm area. 

A carbon-fiber yarn is an assembly of monofilaments held together by a twist. Yarns are usually composed of continuous filaments or, in some cases, of discrete filaments (staple yarns). Woven fabrics are usually processed from yarns comprising several thousand monofilaments. 

Another model eonsidered the fabrie to be substituted by an equivalent perforated sheet which effectively was a solid equivalent polymer sheet as the previous case, but this time covering a fraction of area of the electrode plates. The authors argued that this fraction could be approximated by the fractional cover of the fabric. The results indicated slight improvement for the second model over the first one for tests carried out with plain woven fabrics made from high density polypropylene monofilaments [8]. Hearle also reported similar models and applied them to calculate the permittivity and loss factor of fiber materials from capacitance measurements of yams using a pair of specially designed conical electrode plates [9-10]. 

Studies on the woven fabrics using plain weaves made from high density polypropylene monofilaments were carried out using ASTM D150 standard method [46]. Four fabrics were used, each of which had different filament diameter, yam spacing, thickness and areal mass density. Each of these fabrics was kept between the capacitor plates and the corresponding volume fraction was calculated from the fabric areal density, density of the fiber and the electrode gap. The effective permittivity of the capacitor system with the fabric was calculated from the recorded capacitance value and the over-all capacitor dimensions using... 

PP monofilaments have found broad application in cordage and fishing nets (which float), and if highly stabilized they are woven into fabrics used for outdoor furniture, tarpaulins, and similar applications. Large filament denier staple is used widely in indoor-outdoor carpets. Also, staple fibers have found major applications in tufted indoor carpets and nonwovens used for diaper, filtration, and civil engineering fabrics. 

Fabrics are divided into three different types of yams monofilament, multifilament, and spun. They can be composed of more than one of these types of bric. Monofilaments are composed of single strands woven together to form a translucent or opaque febric. Very smooth in appearance, its weave is conducive to eliminating blinding problems. 

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