Passive damping of laminated composite materials with engineered defects

Constrained layer damping (CLD) methods provide significant damping in laminated composite materials in bending modes. CLD treatments also provide damping mechanisms in axial modes in structures with significant free edges. Where free-edges are absent such as in cylinders or plates with fixed edges, the damping of axial modes in the structure is limited and damping of bending modes is reduced. This paper investigates an alternate passive geometric treatments that improve damping in constrained layer composite materials. In particular, the effect of including strategically-placed geometric anomalies or wrinkles in laminated composite materials is presented. Correct placement of the anomalies result in increased damping in axial modes due to the three-dimensional stress state created in the viscoleastic layer near the anomaly. Because this method does not depend on strain energies created at the free edge, effective damping of axial modes in cylinders may be realized. A closed-form solution is derived that can be used to conduct parametric design studies. Design parameters include defect placement, defect geometry, and composite material properties.