Warfighter protection against blast / ballistic / directed energy threats via lightweight, wearable, reconfigurable colloidal gels.
Abstract
War fighters are exposed to blast pressure emerging not only from bomb explosions but also operation of blast-intensive weapons syst"ems like recoilless rifles, shoulder-fired rockets, artillery and mortars. While the pressure waves associated with weapons operatio""n are less intense than explosions,exposure is frequent, close by, and in a confined space between the warfighter and the weapon ~"" three things that combine to amplify long-term damage. When a blast wave propagates toward the body, part of the energy passes thou""gh it. The brain for example effectively acts as an energy dissipater, and does so over many wavelengths associated with the spectru"m of length scales present in the physical structure of brain matter. This proposal seeks to address directly the need to shield the" brain from multi-scale wave damage, by providing a soft, lightweight material with multi-hierarchical structure that will store and"" dissipate the energy associated with such waves, before they get penetrate into the brain.The design of protective helmets for na"vy warfighters has seen several advances in the management of damage arising from ~secondary~ blast injury ~ that associated with fr"agments and projectiles. Energy-absorbing metal alloys, micro-structured materials, and lightweight Kevlar have all proven effective"" strategies for preventing penetration of such projectiles into the body. Inside a helmet, shock-management solid materials have att"empted to provide progress in reducing concussions associated with the ~primary~ injury in blast-body and blast-brain interactions: linear and torsional relative acceleration of the bulk brain mass. While such materials address some acceleration of the body and h"ence relative motion inside the body, they cannot dissipate all wave energy within these materials, which subsequently dissipates in"" the multitude of interfaces within the brain for example, leading to potential multi-scale physical damage. Some of these approache"s do leverage multi-hierarchical length scales but are constructed only of solid-phase materials that remain in the solid phase. Eve"n the most mechanically compliant solid dissipates only a fraction of deformation energy, and storage of energy in elastic deformati""on is restricted to very high frequencies. Thus, such materials are inherently limited to a narrowrange of blast injury.We propos"e to develop a multi-hierarchically structured colloidal gel that exhibits an on-demand transition from solid-like to liquid-like ch"aracter and back, with a tunable mechanical response that includes multistep fluidization by the use of sequentially breakable netwo"rk elements(strong/extensible tethers and weaker/sacrificial tethers). The resultant material will be successful owing to three features: (1) autonomous adaptability to a very wide range of incoming waves; (2) lightweight composition; (2) infinite reset/reusabili"ty. In feature (1), the transition from solid to liquid state is characterized by a saturation of energy storage at a well-defined p""eak stress and strain, followed by an energy release via structural rearrangement and viscous dissipation. The energy landscape of t""his transition can comprise a multitude of onset rates that correspond to blast wave frequency, and a multitude of maximum energy st"orage values that correspond to blast wave intensity. No a priori knowledge of incoming blast energy is required: the material can b"e designed to handle a wide spectrum of intensities and frequencies. For feature (2), the solid content can comprise a volume fracti""on as low as 20%. For feature (3), the material can be rejuvenated on-the-fly via manual re-distribution, as simple as manually mass""aging a packet of gel.The proposed research will lead to highly-responsive, lightweight, renewable-on-the-fly blast protection for"" war fighters, extending current protection beyond secondary injury (shrapnel, projectiles) and acceleration-related primary injury"" (concussi
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 23, 2018
- Source ID
- N000141812105
Entities
People
- Roseanna N Zia
Organizations
- Office of Naval Research
- Stanford University
- United States Navy