Abstract
In this paper, the results of the experimental investigation into the addition of indentations of power-law profile into composite plates and panels and their subsequent inclusion into composite honeycomb sandwich panels are reported. The composite plates in question are sheets of composite with visible indentations of power-law profile. A panel is a sheet of composite with the indentations encased within the sample. This makes a panel similar in surface texture to an un-machined composite sheet (reference plate) or conventional honeycomb sandwich panel. In the case of quadratic or higher-order profiles, the above-mentioned indentations act as two-dimensional acoustic black holes for flexural waves that can absorb a large proportion of the incident wave energy. For all the composite samples tested in this investigation, the addition of two-dimensional acoustic black holes resulted in further increase in damping of resonant vibrations, in addition to the already substantial inherent damping due to large values of the loss factor for composites. Due to large values of the loss factor for composite materials used, there was no need in adding small pieces of absorbing layers to the indentations to achieve desirable levels of damping.
Highlights
Composite materials and structures are found in an increasing variety of applications in aeronautical, automotive, and marine industries, where they replace many parts and components traditionally made of metals and metallic alloys
The aim of the present paper is to investigate vibration damping in glass fibre composite plates and panels using 1D and 2D acoustic black holes
It was found during initial testing that a composite sample, unlike the steel samples, required no additional damping layer to be attached to the wedge tip to produce the acoustic black hole effect
Summary
Composite materials and structures are found in an increasing variety of applications in aeronautical, automotive, and marine industries, where they replace many parts and components traditionally made of metals and metallic alloys. The main advantages of composite structures over their metallic counterparts are their higher stiffness-to-weight ratio and better resistance to corrosion. Another useful feature of composite materials is higher values of their intrinsic energy loss factors, which results in lower levels of undesirable structural vibrations under the same operational conditions. Passive damping of structural vibrations is achieved by adding layers of highly absorbing materials to the structure in order to increase elastic energy dissipation of propagating (mostly flexural) waves [4,5,6]. The main disadvantage of this approach is the necessity to attach rather thick layers of absorbing materials
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