Preliminary investigations into the mechanical properties of a novel shock absorbing elastomeric composite

Impact absorbing pads, filled with an elastic fluid, consisting of numerous, small elastomeric capsules and a viscous matrix liquid are described. The capsules can take many forms, including beads of expanded foams, bubble packing and air filled, open ended tubes. The matrix liquid contributes lubrication, viscous damping and pressure equalisation properties. Preliminary experimental results relating to the impact absorbing and pressure equalisation characteristics of pads of the fluid are presented. The pads exhibit bulk compression characteristics, unlike elastomeric foams, which normally exhibit uniaxial characteristics, during impacts. A practical consequence of this difference is that elastomeric material, inside the pads, to the sides of the impact zone, participates in absorbing impact energy. The impact absorbing characteristics of the pads are less dependent on the shape of the contact face of the impacting body, compared with elastomeric foam impact absorbers, but uniaxial stiffness decreases, as the size of the pad, relative to the impact zone, increases. Pads, as described, have a wide range of medical, sports and transport engineering applications. Vehicle bumpers, based on the concept, could provide the pedestrian protection required by new European legislation, without sacrificing the low speed impact protection of stiff, foam filled bumpers. (C) 2001 Elsevier Science B.V. All rights reserved.