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An innovative technology now makes it possible to damp stiff composite structures more thoroughly by inserting viscoelastic rubber in the core of the structure. The concept provides improved shielding performance and a reduction in vibration and noise.
(Published on June-July 2005 – JEC Magazine #18)
BY JÉRÔME CHEMIN, ASSISTANT MARKETING, SMAC
SMAC CDS®, developed by SMAC, uses an exclusive Smactane® rubber formulation that provides high damping performance over a wide temperature and frequency range. Rubber sheets, usually 1mm thick, are inserted in the structure during manufacturing like a composite ply. They are designed to withstand the curing process and bond to the plies. Under the structure’s flexural modes, the viscoelastic rubber is sheared between the composite plies and dissipates vibrating energy, then noise. This solution has been developed to meet an aircraft manufacturer’s noise-insulation requirements and to damp tennisracket vibrations. The concept has numerous applications in fields ranging from aeronautics and defence to leisure and sports.
The concept allows combining the composite structure’s low weight and resistance with vibration- and noise-damping comfort. The compact, lightweight solution only slightly modifies the structural density (typically 1.2kg/sqm). The manufacturing process is compatible with all composite materials (glass, carbon, Kevlar®, honeycomb, etc.).
This innovative system offers very good acoustic and damping performance, thanks to the rubber’s high damping properties. In a sandwich panel, it damps eight times more than a traditional structure with the same weight, stiffness and thickness. Due to the rubber’s viscoelasticity, the noise reduction is about 13 dBSIL3 (1,000, 2,000 and 4,000 Hz). The technology also improves the shielding performance of composite structures against bullets or gravel, thereby increasing the life expectancy of the composite.
The main applications for this technology are: - Composite structures for air- and spacecraft - Dampened aircraft interiors - Skis and snowboards - Loudspeaker casings - Chassis and protective fairings.