Products and solutions, 2001-09-11, 02:00 AM
Vibration-damping composite in autobody construction
BONDAL®, a sound-damping three-layer composite sheet material from Thyssen Krupp Stahl AG, has a bright future in automotive bodymaking applications. Trials carried out by a leading German automobile manufacturer using a dash panel made of BONDAL® in a production model revealed its silencing properties to be significantly superior to those of the original panel, prompting the company`s acoustics specialists to recommend it unreservedly for future models.
BONDAL® comprises two 0.3 to 1.5 millimeter thick steel sheets with a 0.05 millimeter thick core layer of viscoelastic plastic. The material owes its silencing properties to the fact that vibrational energy in the outer sheets is converted into frictional heat when they slide back and forth on the inner plastic layer.
In car bodies, the dash panel separates the power plant from the passenger compartment. To minimize engine noise, automobile manufacturers nowadays resort to so-called secondary measures, i.e. affixing thick layers of soundproofing material to the dash panel. For example, the model in which the BONDAL® dash panel was tested normally features bitumen mats for noise insulation. The BONDAL® dash panel not only displayed greater acoustic efficiency, it is also easier to produce and considerably lighter than the standard bitumen-lined panel.
Although autobody applications are a new prospect for BONDAL®, it is already firmly established in engine and transmission add-ons. For example, the BONDAL® H variant used to manufacture transmission covers allows a 37 percent weight reduction versus bitumen-coated parts while providing the same acoustic performance. Moreover, one complete operation can be dispensed with during the production process.
As different temperatures affect the viscoelasticity of the intermediate plastic layer, Thyssen Krupp Stahl AG has developed three BONDAL® variants. BONDAL® H is suitable for high temperatures of 50 to 130°C, BONDAL® M covers the medium range from 25 to 110°C and BONDAL® N is designed for temperatures from minus 10 to 70°C. The steel outer sheets can be of any grade, galvanized or uncoated; depending on requirements it is even possible to use stainless steel or aluminum sheets. BONDAL® can also be supplied coil coated, making it unnecessary to paint the finished component.
The composite material displays similar fabricating properties to solid sheet. It can be cut to length using both conventional and more recent methods such as laser or water-jet cutting. BONDAL® is suitable for deep-drawing and stretch-forming using standard tooling and is ideal for joining by clinching, bolting, riveting or bonding. Resistance spot welding has proved the most successful method for welding.
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