Stopping km/s Blunt Fragments and Limiting Shock Lensing with a
New Advanced Energy Absorbing Composite
Gareth R Tear
1
, Gianmaria Bullegas
1
, Jose Videira
1
1
Synbiosys Ltd., UK
gareth@synbiosys.co
Abstract We are developing a lightweight ceramic/polymer composite for km/s fragment
resistance. It uses a fundamentally new physical process for energy absorption that
complements the conventional forms of energy dissipation of fracture and plastic
deformation. This composite comes into its own against very high impact velocities, being
able to provide protection in shock regimes where conventional materials like kevlar and
steel can be considered incompressible fluids with zero protection capabilities.
!
This material can be used in rocket motor casings for increased IM compliance. It can
absorb and dissipate energy extremely quickly (of the order of 100kJ/m2/μs). Crucially it
limits shock lensing effects, augmenting current capabilities against blast and shaped
fragments. The energy dissipation mechanism propagates at 7km/s inside the material and
activates with minimal (<2%) overall strain of the structure. The design of the composite is
flexible enough to be optimised for a range of projectile threats and velocities.!
!
In practical terms, the composite has the same density as aluminium and is made from
cheap raw materials. It can also be made transparent, enabling applications beyond rocket
motor casings into protective blast windows.!
!
We present here experimental verification of our fundamental energy absorbing process
through plate impact experiments, taking measurements by interferometry (PDV) and high-
speed videography. We demonstrate that this process does provide a significant (20m/s)
decrease in rear surface velocity in plate impact experiments.!
Introduction
Shock to Detonation Transition (SDT) is one of the phenomena limiting effective energetic
materials for use in dangerous environments. Explosive efficiency, whether measured by
weight, impulse or another metric, is sacrificed to achieve the low sensitivity demanded by
Insensitive Munition (IM) requirements. Traditionally IM technology has focused on
chemically developing explosives and compositions which have low intrinsic sensitivity. In
this paper we present a mechanical mechanism for dissipating hot spot formation and
attenuating shock fronts directly, allowing more efficient explosive compounds to be used,
whilst maintaining the munitions overall IM compliance.
The mechanism has been implemented into a composite form of protection, offering the
ability to absorb energy at the shock front, reducing the strain rate on the material behind the
composite. It achieves this with less than 2% strain, making it a viable composite for
protecting energetic material. The mechanism attenuates energy at the shock front, and can
prevent the large transient impulses characteristic of shock waves and particularly
dangerous to energetic material.
Vision for the composite technology
The composite has a density of around 2.5g/cm
3
. The raw materials can be considered
abundant and will cost around $2000 - $5000 per ton to purchase, and the manufacturing
involves traditional composite construction techniques with temperatures not exceeding
200°C.
