This paper presents an experiment testing the damped free vibration of a system composed of a magnetorheological elastomer and a mass. The goal of this experiment was to obtain the dependence of the natural frequency and the damping ratio of the structure on the applied magnetic field. The shear properties, including the shear storage modulus and the damping factor, were therefore determined. The experimental results revealed that the shear storage modulus could reach a value of 60% of the zero-field modulus and was dominated by the magnetic field, but the change in the damping factor could be neglected. Furthermore, when the field was moderate and saturation did not occur, the shear storage modulus increased proportionally with the applied field. This interesting phenomenon was analysed, and it is suggested that the subquadratic field dependence, which arises from the saturation of the magnetization near the poles of closely spaced pairs of spheres, must be taken into consideration.

A state-of-the-art review is presented regarding the research and development of in situ fibre optic damage detection and assessment systems (FODDAS) embedded in fibre-reinforced composite structures. Representative individual fibre optic strain sensors and distributed sensor networks are briefly described. A major emphasis is placed on their capabilities for detecting damage, determining damage location and assessing the nature of damage, arising primarily from specific events such as impacts or quasi-static stress overloads. The main features of such systems as custom-built and structure-specific units with minimal human involvement are highlighted. Issues that could affect the validity of the performance of such strain sensors are discussed. Fracture and non-fracture of fibre optic sensors are identified as two fundamentally different approaches for damage detection and their primary features are discussed in relation to location determination and evaluation of the nature of damage. The major advantages and limitations of each approach are discussed. Directions and areas of potential future research in the development of related FODDAS are highlighted.

Magnetorheological elastomer (MRE) is a new class of smart materials, whose modulus can be controlled by the applied magnetic field. In this paper, using a white light speckle technique for deformation analysis, we present the real-time dynamic deformation progress (the vector diagram of the displacement or the whole-field quantitative displacement distribution) of the MRE and the elastomer–ferromagnet composite (EFC) while the magnetic field is turned on. The experimental results verify the prediction presented in a recently published paper, (Borcea and Bruno 2001 J. Mech. Phys. Solids 49 2877–919), and reveals some interesting phenomena which will give us a deeper understanding for such smart materials.

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Damage characteristics of composite-skinned honeycomb sandwich panels in bending are investigated with both hemispherical (HS) and flat-ended (FE) indenters. The thickness of the cross-ply skins varies from 8 to 16 plies, whereas the density of the 12.7-mm thick aluminum honeycomb core varies from 50 to 70 kg/m 3 . Clamped panels with a 100-mm testing area are loaded quasi-statically either in bending or on a rigid base. The effects of varying these parameters on damage mechanisms are examined through response curves as well as cross sections of selected specimens. Special emphasis is placed on their potential change induced by the variation of skin thickness and core density with a specific indenter. Damage mechanisms are identified as core crush, top-skin delamination, and fracture or shear-out. The threshold and ultimate loads as well as the initial slope increase significantly either on increase of skin thickness or change of the nose shape of indenter from a hemisphere to a flat-end. The increase in the post-initial-damage slope is small and can be attributed to membrane stretching of the damaged top skin. Increasing the core density affects substantially not only the threshold load, but also the initial slope associated with the FE indenter. Changing the nose shape of the indenter has an overriding effect on the nature of damage mechanisms. In particular, top-skin delaminations occur after core crush. The panel deflection contributes to 20-53% sandwich deformation. The bottom skin in all the tests remains intact.