Vibration Damping of Flexible and Rigid Polyurethane Composites

It is desirable to obtain materials that have high vibration damping while maintaining other structural properties. Aerospace quality composite materials typically have greater strength and stiffness to weight ratios than most metals, while providing increased damping. However, their passive damping capacities are not enough for some applications. Fiber reinforced elastomers (FRE) or elastomer composites are receiving attention because of the ability to tailor their vibration damping, strength, fracture toughness, and elongation to the range needed. The current work considers a series of aluminum panels that are laminated with “skins” of graphite cloth, fiberglass cloth, and with chopped fiberglass mat. The reinforcements are impregnated with a series of polyurethane elastomers that range from flexible to rigid in hardness. For a given type of fiberglass, the lower durometer elastomer produced the highest loss factor. For a given elastomer stiffness, the stiffest reinforcement produced the highest damping. In general the skin loss factors are inversely proportional to the equivalent axial in-plane stiffness of the composite. Skin loss factors range from 1.5% to approximately 20%. The study provides valuable experimental data that will be useful in developing flexible or rigid lightweight and cost-effective materials that provide good damping while contributing strength and stiffness.