It was also found that there is a direct relationship between weight per m2 and sound absorption efficiency. Samples produced with 55% polyester/45% hollow polyester fibers and 600 g/m2 have achieved the best results. Keywords: Nonwoven Fabrics, Hollow Fibers, Cars Interior Acoustic Properties, sound Insulation 1. Introduction frequently used in automotive interiors to reduce heat levels (Imfeld et al. as customers expect more comfort, better safety, good appearance (both externally and internally), high performance and good fuel mileage (Mukhopadhyay, 2000). Textiles make a major contribution towards realizing customers’ expectations due to their advantages which made textiles a preferable material because of their high capacity to take moisture, adjustable porosity, high-pile fibrous surface, low-cost recycling, and the flexibility and diversity in combining textiles with other materials. Bottcher, 2005). Due to the diverse product range, automotive textiles can be classified into upholstery and carpeting (Desai ,2005) which have a decisive influence on acoustic comfort (Laser, 1997) interior components such as head liners, and doors and side panels (Desai, 2005) which are foam backed components to achieve easier installation and improve acoustical properties (Waugh, 1986) and tyres, safety devices (such as seat belts and airbags), filters and engine compartment items (Desai, 2005).
When talking about textiles, most people think of clothing, home textile and the like. Only few think about the automotive industry (Wilkens, 2005). In fact, automotive textiles are considered one of the most important markets in the technical textiles sector (Mukhopadhyay, 2000). Over the last decades, the field of non-conventional textiles has been witnessing a material revolution which has resulted in improved and economical products (Tilgul, 1990).
The automotive industry has become so competitive that manufacturers are reluctant to divulge precise details of their process for fear that textiles are widely used in transportation vehicles and systems, including cars, trains, buses, airplanes, and marine vehicle (Fung and Hardcastle , 2001) automotive textiles are growth markets in terms of quantity, quality and product variety (Parikh et al. , 2002). it could be helpful to their competitors.
Industrial Motor vehicle remains an important means for individual transport worldwide. The interior of transportation vehicles is receiving more attention these days. Acoustical insulation products are * Corresponding author. Tel. : 0020105199359, Fax 0096664224273 E-mail address: [email protected] com (Ghalia El-Shenawy) 49 RJTA Vol. 16 No. 3 Aug 2012 1. 1. Noise in Cars Noise has become serious environment pollution in our daily life and is an increasing public health problem, as noise can cause erious health effects such as hearing loss, sleep disturbance, tiredness, cardiovascular and psychophysiologic problems and performance reduction. It is very important to control or reduce noise from traffic, and in factories, offices and houses (Lou et al. , 2005). Car noise is essentially caused by the unit sound, the exhaust system noise, the air suction, noise, rolling and wind noises (Helmer, 2002).
Today, the dominant approach to achieving interior quietness relies to a large extent upon the ability to create impermeable enclosures around vehicle occupants through the use of several heavy interior layers (sound transmission loss), but recently a new concept has been emerged suggesting that sound can be reduced by replacing reflection (sound transmission loss) with dissipation (interior sound absorption area) by eliminating heavy barrier layers with light weight porous materials (Buskirk & Middleton, 1999).
Nonwoven is employed as fabrics for different kinds of interior applications. The numerous applications of nonwoven in cars can be classified into functional and aesthetic but there is a third category that of substitutes for other materials. Nonwoven can be made in a wide range of densities and different forms; the use of nonwoven is increasing because it offers great versatility and cost effectiveness (Adanur, 1995). Each vehicle requires about 20 m2 of nonwoven materials (Lou et al. , 2005) which are used specially for insulation, noise dissipation and as filter materials.
Woven and knitted fabrics are also used in producing automotive fabrics but to a lesser extent compared to nonwoven fabrics (Hilden, 2002). 1. 2 Hollow Fibers (nitrogen) in the polymeric solution (in the wet spinning process) or by melt spinning through specially designed spinnerets (Hoechst Celanese Corporation , 1990). Hollow fibers provide greater bulk with less weight; they are therefore often used to make insulation fabrics (Tortora & Phyllis, 2002). 2. 2. 1 The Experimental Work Specification of Samples Under Study In order to produce samples under study, the nonwoven technique was applied using cross-laid fiber orientation.
Two kinds of textile materials were used: polyester and hollow polyester fibers, both of 6 denier, to produce three different fabrics of 100% polyester fibers, 75% polyester and 25 % hollow polyester fibers and 55% polyester/ 45% hollow polyester fibers. Four fabric weights were also produced: 300, 400, 500,and 600 g/m2 . All samples were bonded using thermal bonding technique (hot air method (by adding a small proportion of low–melting point polyester fibers (about 15% and melting point of 110oC). Tables (1) and (2) illustrate the specification of all sample production. 2. Tests Applied to Samples Under Study Hollow fibers are polymeric fibers that have a continuous hole running down the middle, which is created by the introduction of air or other gas In order to evaluate the performance properties of the produced samples, the following tests were carried out. Test 1: Sound absorption coefficient, this test was carried out according to the ASTM – E 1050-1982. The sound (noise) absorption values (%) of samples under study were measured at 6 different frequencies: 125, 250, 500 Hz (low frequency tube) and 1000, 2000, and 4000 Hz (high frequency tube).
Test 2: Air permeability, this test was carried out according to the (ASTM-D 4491-92) Test 3: Fabric thickness, this test was carried out according to the (ASTM- D -1777). 50 RJTA Vol. 16 No. 3 Aug 2012 Table 1. Specification of samples production Sample No. 1 2 3 4 5 6 7 Property Fiber type Fiber count Fiber length Fabrics material Web formation Fabric weight (g/m ) Bonding technique 2 Specification Polyester and hollow polyester fibers 6 denier 64 mm 100 % polyester fibers ,75 %polyester /25 % hollow polyester fibers and 55 % polyester / 45 % hollow polyester fibers. Cross-laid 300,400,500 and 600 Thermal bonding
Table 2. Specification of all samples under study Sample no. 1 2 3 4 5 6 7 8 9 10 11 12 Fabric weight (g/m2) 300 300 300 400 400 400 500 500 500 600 600 600 Fabric material 100% polyester fibers 75% polyester /25% hollow polyester fibers 55% polyester /45% hollow polyester fiber 100% polyester fibers 75% polyester /25% hollow polyester fibers 55% polyester /45% hollow polyester fiber 100% polyester fibers 75% polyester /25% hollow polyester fibers 55% polyester /45% hollow polyester fiber 100% polyester fibers 75% polyester /25% hollow polyester fibers 55% polyester /45% hollow polyester fiber 51 RJTA Vol. 16 No. Aug 2012 Table 3. Results of all tests applied to samples under study Tests Sound absorption (%) Air permeability (cm3/cm2/sec)