Development of Composite Materials with High Passive Damping Properties.

摘要

In applications where the use of lightweight structures is important, the introduction of a viscoelastic core layer, which has high inherent damping, between two face sheets, can produce a sandwich structure with high damping. Composite sandwich structures have several advantages, such as their high strength-to-weight ratio, excellent thermal insulation, and good performance as water and vapor barriers. So in recent years, such structures have become used increasingly in transportation vehicles. However their fatigue, vibration and acoustic properties are known less. This is a problem since such composite materials tend to be more brittle than metals because of the possibility of delamination and fiber breakage. Structures excited into resonant vibration exhibit very high amplitude displacements which are inversely proportional to their passive damping. The transmission loss of such composite panels is also poor at coincidence. Their passive damping properties and aftempts to improve their damping at the design stage are important, because the damping properties affect their sound transmission loss, especially in the critical frequency range, and also their vibration response to excitation. The research objects studied in this ONR project are polyurethane foam-filled honeycomb sandwich structures. The foam- filled honeycomb cores demonstrate advantages of mechanical properties over pure honeycomb and pure foam cores. Previous work including theoretical models, finite element models, and experimental techniques for passive damping in composite sandwich structures was reviewed. The general dynamic behavior of sandwich structures was discussed. The effects of thickness and delamination on damping in sandwich structures were analyzed. Measurements on foam- filled honeycomb sandwich beams with different configurations and thicknesses have been performed and the results were compared with the theoretical predictions.