Increased use of thermoset and thermoplastic composites in underhood and trim applications in the automotive industry has heightened the interest in gauging and improving their NVH (noise, vibration, and harshness) characteristics. In addition to material damping properties, other properties such as mass, stiffness, and architecture also play a large role in determining the overall NVH behavior of automotive components. Mechanical properties and damping characteristics of hardwood and softwood cellulose fiber and hemp fiber reinforced polypropylene and nylon 6 composites were studied. Mechanical properties were evaluated by standard ASTM methods. Material damping was analyzed by means of dynamic mechanical thermal analysis (DMTA). Solid structure-borne damping of components was investigated by modal analysis and frequency response modeling. Preliminary measurements of storage and loss moduli and phase lag from DMTA show that the material damping of natural fiber reinforced plastics may provide higher material damp- ing than unreinforced and glass fiber reinforced plastics.
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