Designing of a Low Weight Dashmat With An Innovative Fibrous Material
Published July 2, 1997 by Associazione Tecnica Dell'Automobile in Italy
In this paper we describe a case study for reducing weight but maintaining same acoustic efficiency of a dashmat, one of the heaviest NVH trimming parts on vehicles (4.5-10 kg). The task was achieved through a numerical optimization of the material multilayers used to construct the part: this kind of approach allowed a weight reduction of 3 kg/sqm without expensive and time consuming trial and error techniques. The multilayer of the new dashmat consisted of a lower weight heavy layer, a stiff and thin textile felt to give self consistency to the part and an innovative fibrous felt layer produced by 3M. This new material (Thinsulate) is a micro-fiber polypropylene and polyester felt with very high sound absorbing and decoupling properties but very low weight (600 gr/sqm). Numerical and experimental optimization of material layers was followed by the prototyping of a complete dashmat that was then tried on the vehicle during track tests and compared with the standard production version. The new solution gave the same acoustic performance as the standard production one even though with 3 kg less of weight. Also the articulation index was the same.
The same kind of approach was used for trimming a complete car with Thinsulate parts: the overall result was a 20% weight reduction, a 1-2.5 dB(A) reduction of sound pressure levels in all the rpm range and a 10% increase in AI.