The stress and ballistic properties of granular materials

Abstract

Abstract. Granular materials are widespread in nature and in manufacturing. Their particulate nature gives a compressive strength of a similar order of magnitude as many continuous solids, a vanishingly small tensile strength and variable shear strength, highly dependent on the loading conditions. Previous studies have shown the effect of composition, morphology and particle size, however, compared to metals and polymers, granular materials are not so well understood. This paper will present some recent results for granular materials, placing these within the wider context. Two areas will be dealt with (i) the effect of the skeletal strength of the material and (ii) the displacements associated with ballistic impact. One clear observation is the similarity of behavior of quartz-sands in compression across a range of particle size. However, the precise pathway of compression is strongly dependent on the initial conditions e.g. density and connectivity within the granular bed, as emphasized by some data for quasi-static compression of sand. To fully embrace the range of behaviours seen requires the development of a suitable parameter to describe the material, the paper concludes with a discussion of one of those approaches.

Numerical modelling study of a modified sandbag system for ballistic protection

“…Sand has been used as a means of protection against blast and ballistic threats for a variety of reasons which are (i) it is ubiquitous; (ii) it is cheap and can be bought in bulk quantities; (iii) it absorbs and dissipates energy effectively; (iv) it has a very high critical velocity; and (v) it is easy to work with and requires little processing before being used in the field [1,2]. The increased dependency on explosive weapon systems developed the need for larger field fortifications which raised questions for the use of sand in these protection systems.…”

“…Previously, studies have focused on the physical properties of sand and how they influence the penetration resistance of the system [2,4,6,13,17,22]. Observing the compaction behaviour and how it changes by modifying the sandbag creates the opportunity to improve the protection system performance with minimal changes to the filling.…”