Some cars, especially sports cars, can be recognised just by their sound. But while some tune their motor for sound, others want efficient damping of the noise. Sekisui Alveo, manufacturer of polyolefin foams, recently helped an OEM find a noise-damping solution for the floor pan – just a few weeks before the sports cars start of production (SOP).
Alveocel, the foam used as the flat absorber, is said to provide optimal acoustic absorption thanks to special processing. It also claims to be robust, and the absorber is able to be easily integrated into the assembly. Finding a new, easy-to-integrate solution for a gear box absorber only a few weeks before the start of volume production – this indeed presents something of a challenge. The carmaker had discussed the problem with the converting supplier, who turned to Sekisui Alveo with this task in June 2013. “The OEM already knew the acoustic performance of our foams from an application in another volume application and knew that our products cover a broad frequency range as absorption material,” explains Thomas Ross, Market Manager Automotive at Sekisui Alveo, describing the initial situation. “It was immediately clear to us that modification of the flat absorber already in use and made of our PP foam Alveocel LP PM would be an elegant solution.” Short-notice feasibility, manageable costs and simple integration and mounting of the flat absorber in the floor pan were other important factors supporting the decision.
Flat yet efficient due to micro-perforation
To cover an especially broad frequency range as an absorber, the Alveocel foam from Sekisui Alveo is micro-perforated with a specific pattern and partially laminated in multiple layers. The converting supplier then die cuts the material into the required complex shape. Even a single layer of the foam provides good acoustic absorption. The absorption is increased by the use of multiple layers of foam. In spite of these layers, the absorber remains flat in comparison with the box absorbers normally used – an advantage considering the limited space between the under-body structure and the floor pan.
Robust with long-term performance
Not only are the dimensions of the absorber and its acoustic effectiveness important, but the material also needs to be robust due to its position close to the gear box and the road. Alveocel is designed for long-term temperature resistance up to 140°C. Furthermore, the PP foam absorbs little water and is inert to a great number of chemicals. Thus temperature fluctuations, moisture, motor fluids, and dirt have no influence on the performance of the weather-resistant material. Its absorptive characteristics and the frequency range are said to remain intact even after many years of service. Sekisui Alveo has already confirmed this using its in-house Alpha Cabin in which engineers test the acoustic absorption properties of the polyolefin foams developed especially for this application.
Sekisui Alveo with head office in Lucerne, Switzerland, develops and produces extruded and crosslinked polyolefin foams, which are used in: adhesive coating, automotive, construction including artificial turf as well as industrial and consumer goods. The product portfolio of Sekisui Alveo contains a wide variety of solutions for the automobile industry: mainly foams that enhance comfort by improving surface feel in the interior, but also foams that provide damping and sealing in NVH (noise, vibration, harness) applications or are used in HVAC (heating, ventilation and air conditioning) applications:
- Armrests, headliner, back shelf, instrument panel, steering wheel, seat bolster / seat reinforcing, sun visor, door panels
- Absorbers, seals (headlights, side mirrors), trunk trim, wheel well liner, seat covers, watershield
- Air ducts