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For generations, fiber felt technologies have been used as a building block in the development of various absorbers and decoupler composites used for automotive acoustics. This development has led to a variety of felt components with increasing complexity in their differentiations. This paper will review the evolution of three generations of felt technologies. Generation 1 and 2 will discuss needled, resinated, and thermoplastic fibers bonded felts by comparing various performance indexes from physical parameters of raw materials, manufacturing processes, product applications and physical characterization along with acoustic properties. Generation 3 will introduce strategies, technologies, and approaches to further simplify the multitude of fiber felt innovations.

The substrate selection for headliner composites is driven by acoustics, systems integration, weight and cost considerations. However, the acoustical contribution of headliners plays a primary role in their design. This paper highlights the acoustical contribution of the various headliner composites. Various current headliner composites based on glass-fiber mat, polyurethane foam, resinated reclaimed fiber composites are considered. New composite structures are developed that exhibit good acoustical performance. The random incident acoustic evaluation is performed in an alpha-cabin which serves as a small reverberation room.

Recycling of resinated and non-resinated reclaimed fiber pad, used in automotive applications as sound absorbers and insulators for headliners, package trays, floor insulators etc., has been ongoing for over thirty years. The feedstock for the fiber is a source reduction of textile industry waste, as compared to alternate first use material products. The fibers are actually reclaimed from apparel trim scrap (approx. 700MM pounds of apparel scrap produced annually). The acoustical trim product uses 60 to 100% of the available reclaim apparel scrap - material originally intended for basic necessities such as clothing, and in the case of resinated pad, blends this fibrous material with a binder resin (this only is a first use material.) During pad production, “pre-use” processing and trim scrap are reclaimed and re-introduced into production, up to 70% loading for resinated pad and up to 100% loading for non-resinated fiber pad.

The development of binder systems for automotive sound insulators as an alternative to phenolic resin is presented. Various thermoplastic binder systems were evaluated. The non-woven airlay process technology was used in manufacturing the padding. Subsequent cold thermoforming techniques were employed to produce molded sound insulators. Material characterization and part performance evaluation of mechanical properties, heat resistance, and acoustical performance were determined. Manufacturing process for the molded sound insulator was also demonstrated. The study concluded that a thermoplastic binder system, as an alternate to phenolic binder resin, can be used to produce functional molded fiber floor insulators.