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Improved constrained-layer damping treatment design for high damping and low interlaminar stresses

The purpose of this research is to investigate and improve constrained layer (CL) damping treatment for high damping and low interlaminar stresses (better durability). In this paper a mathematical model is developed to calculate interlaminar stresses in a CL treatment. The model is based on the Built-Up Bar (BUB) theory but includes numerous fundamental modifications to handle the behavior of various coversheet and viscoelastic materials. A parametric study is conducted. It is shown that the interlaminar peeling and shearing stresses in a CL treatment could be very high, especially at the free edges due to discontinuities in the material properties. It is also illustrated that these interlaminar stresses are of local type, i.e. the high stresses are limited to a region that is close to the free edge and is of the same order-of-magnitude in length as the layer thickness. The observation is that the designs that provide high damping usually have high interlaminar stresses. This means that the existing high performance CL designs that provide high damping usually have high interlaminar stresses.This means that the existing high performance CL designs could fail, especially under high load operations. From this research, it is shown that through some simple yet innovative modifications (e.g., slightly tapering the constraining layer at the free ends), the interlaminar stresses in the CL treatment can be significantly reduced while maintaining high levels of damping.