Nonwoven Fabrics Literature Review

Chapter 2

Literature Review Nonwoven fabrics are produced directly from a web of fibres rather than from interlacement of yarns. There are a number of techniques for producing nonwoven fabrics like, adhesive bonded, needle punched, thermal bonded, stitch bonded, hydroentangled etc., These fabrics find applications in various field like filtration, geo textiles, interlinings, wipes, garments, medical textile products, as composites in civil engineering etc., Within a very short time a considerable amount of research work has been carried out to have a better understanding of the properties and applications based on the end-use requirements. The relationship between the structure and properties of various types of nonwoven fabrics is well documented.

The standard measurement of tensile strength is done as per EN ISO 20973 at a 200 mm test length and extension rate of 100 mm/min and has been adopted by researchers in reporting the tensile strength of nonwoven fabrics. However, during real time use the fabric lengths may be shorter or longer and the stresses experienced are different. As a first step towards characterising the factors that influence the rendition of the fibre properties into fabric behaviour in the case of hydroentangled nonwovens, the effect of tensile test gauge lengths on fabric strength and the type of failure was analysed. Weibull, (1951) introduced an empirical distribution based on the “weakest link” theory, developed earlier by Pierce (1926). The “weakest link” theory applies in situations that are analogous to the failure of a chain when one of its links has failed. The Weibull distribution has been used in a wide variety of applications, including mechanical testing data from material specimens with defects. The distribution function of the Weibull distribution which models the extreme values due to the “weakest link” concept is expressed

The Weibull distribution is used in this study to characterise the tensile behaviour of hydroentangled nonwovens when tested at different test lengths. Many research studies have been done (Realff et al., (1991), Gosh et al., (2004), Rengasamy et al., (2005), Triyakioglu et al., (2009), Pan et al., (2002), Shaha et al., (2011), Shao et al., (2013), Wang et al., (2014), Hashim et al., (2016) analysing the tensile failure mechanism of fibres and yarns using Weibull analysis. Some of these studies have analysed and validated the data to fit to two-parameter Weibull distribution. However, tensile behaviour of hydroentangled nonwovens as a function of test length has been hardly ever studied and the use of Weibull distributions to fit the fabric strength data is not available. Triyakioglu has recommended due to the destructive nature of testing involved in these studies of estimating the tensile strength at different test lengths and the small number of repetitions using one of the three methods: (i) linear regression, (ii) maximum likelihood, and (iii) moments. The linear regression because of its simplicity is used in this study to estimate the shape and characteristic values and verified for goodness of fit using the Kolmogorov–Smirnov goodness-of-fit