Characterization of the Core Properties of a Shock Absorbing Composite

Abstract

This paper is on the characterization of the mechanical properties of Newtonian-type shock absorbing elastomeric composites. This composite material is a blend of elastomeric capsules or beads in a matrix of a Newtonian liquid. The material can be considered as a liquid analogy to elastomeric foams. It exhibits bulk compression characteristics and acts like an elastic liquid during an impact, unlike elastic foams, which exhibit uniaxial compression characteristics. A test cell consisting of an instrumented metal cylinder and a piston was designed. A sample of the material was placed in the instrumented cylinder, which was located at the base of a drop test rig. A drop mass of 17.3kg was subsequently released from a desired height to impact the piston. From measurements of the acceleration histories of the drop mass and the piston, and from the displacement history of the piston, the force-displacement curves and the associated impact energies absorbed were derived. These are compared to the corresponding characteristics derived from measurements of pressure of the fluid medium inside the cylinder. The results are compared for blends of different bead types, and the different aspects contributing to their performance are discussed. It is shown that the performance curves derived from the accelerometer measurements matched those derived from the pressure measurements. Blends of this composite material of different types of beads showed distinctively different characteristics.