Lightweight damping of composite sandwich beams: Experimental analysis

Abstract

The purpose of this article is to experimentally study the damping of composite sandwich beams with lightweight honeycomb core. The top and bottom facesheets are made of carbon/epoxy layers with partial interleaved viscoelastic layers. A new damping approach consisting of selectively targeting the inflection points of the bending mode shapes is proposed. At the nodes, the shearing deformation in the beam is maximal, and so is the strain in the viscoelastic layers. The experimental investigation of damping is made by means of standard impact tests using an instrumented hammer performed on beam specimens. The nodes are determined experimentally by moving a small accelerometer along the beam axis and by measuring the amplitude of the acceleration at each point. This novel damping approach keeps the damping ratio as high as the ratio obtained with standard (full coverage) surface damping treatment while reducing the added mass by almost 50%. A comparison of the results obtained in this study with experimental and numerical results found in the literature leads to the conclusion that the most efficient way of damping this type of sandwich structure is to modify and/or improve the viscoelastic properties of the core.

Numerical analysis of shear stiffness of an entangled cross-linked fibrous material

“…However, it presents many drawbacks, such as the difficulty implementing it in complex structures, closed porosity and difficult quality control processes. The low vibration damping is still the most important problem with the honeycomb structure, and many methods have been presented to enhance the damping of the sandwich structure ( Cai et al, 2004;Fotsing et al, 2013;Li, 2006 ).…”

A C0-continuous RZT beam element for the damped response of laminated structures

“…However, ESLT implicitly assume that not only the displacements are continuous at layers' interface but also their derivatives, in contrast with the elasticity solution obtained by Pagano [8], which clearly shows a piecewise distribution of the axial displacements in the thickness direction. This, in turn, causes inaccuracies in predicted laminates response: transverse stresses are responsible for delamination at free edge proximity [9], shearing is the main contributor to energy dissipation in viscoelastic cores and soft layers [10][11][12] and more generally, ESLT assumptions are no longer valid for thick structures [13,14]. In the attempt to give a more accurate description of the phenomena occurring within laminates, at the same time limiting the cost of computations, zigzag theories have been proposed by several authors [15][16][17].…”

Experimental dynamic analysis on naturally curved honeycomb sandwich beams with different damage patterns

“…made an experimental investigation of damping by means of standard impact tests using an instrumented hammer performed on composite sandwich beam specimens [6]. In the experimental analysis, the nodes were determined by moving a small accelerometer along the beam axis.…”

“…Im zweiten Teil wurden Fallversuche und Schwingungsversuche durchgeführt, um das freie Schwingungsverhalten des beidseitig fest eingespannten Wabenkernsandwichbalkens mit Rissen und einer Aufprallregion zu bestimmen. Entsprechend dem Schadensmuster des Sandwichbalkens besteht die dynamische Analyse aus den folgenden sechs Schritten: (1) Schwingungsanalyse ohne Riss und Aufprallregion, (2) Schwingungsanalyse ohne Riss aber mit Aufprallregion, (3) Schwingungsanalyse mit Oberflächenriss aber ohne Aufprallregion, (4) Schwin-gungsanalyse mit Oberflächenriss und Aufprallregion, (5) Schwingungsanalyse mit zwei Oberflächenrissen aber ohne Aufprallregion, (6) Schwingungsanalyse mit zwei Oberflächenrissen und Aufprallregion. Dazu wird ein Schlaghammer mit Kraftaufnehmer genutzt, um die geschädigten und ungeschädigten, natürlich gekrümmten Wabenkernsandwichbalken anzuregen.…”