ballistic helmet standard technologies for critical incident preparedness conference and exposition...
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Ballistic HelmetBallistic HelmetStandardStandardBallistic HelmetBallistic HelmetStandardStandard
Technologies for Critical Incident Preparedness Conference and ExpositionTechnologies for Critical Incident Preparedness Conference and Exposition
San Francisco, November 6-8, 2007San Francisco, November 6-8, 2007
TCIP Conference and Exposition, November 6-8, 2007
MotivationMotivation• new lightweight composite helmets
have increased protection against penetration
• non-penetrating impacts may results in large backface deformation
• increase risk of serious skull/brain injuries ?
• current test procedures address penetration resistance but lack injury risk evaluation for non-penetrating impacts
TCIP Conference and Exposition, November 6-8, 2007
R&D ReviewR&D Review
mid 90’ DRDC Valcartier initiated study on backface impact force / deformation
1997 NATO BABT TG001
2000 Natick Soldier Center: developed skull fracture injury function (UVa)
2002 TSWG funded development of ballistic helmet test method
2005 TSWG funded additional efforts to evaluate threat severity
TCIP Conference and Exposition, November 6-8, 2007
U.S Army NSC R&D ProgramU.S Army NSC R&D Program
• Research approach:• Identify injury mechanism• Determine physical response measurement• Develop injury function• Develop physical surrogate
• Work conducted by Bass et al. (University of Virginia
TCIP Conference and Exposition, November 6-8, 2007
Injury FunctionInjury Function
animal modelcadaver modelepidemiology
Injury Model
Physical Responseloads, acceleration, etc.
Surrogateloads, acceleration, etc.
TransferFunction
TCIP Conference and Exposition, November 6-8, 2007
Injury FunctionInjury Function
animal modelcadaver modelepidemiology
Injury Model
Physical Responseloads, acceleration, etc.
Physical Response
Prob
abili
ty o
f in
jury
Surrogateloads, acceleration, etc.
Physical Response
Prob
abili
ty o
f in
jury
TransferFunction
TCIP Conference and Exposition, November 6-8, 2007
OutcomesOutcomes
• Skull peak pressure is best correlated with injury
• Injury function for non-penetrating ballistic impacts 0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Skull Peak Pressure
Inju
ry r
isk
No Fracture
Fracture
TCIP Conference and Exposition, November 6-8, 2007
NIJ Standard 0106.01 (1981)NIJ Standard 0106.01 (1981)Penetration Resistance• Limited number of test samples
required:• 2 helmets / test ammunition• 1st helmet tested at ambient
conditions• 2nd helmet wet-conditioned
(immersion 2-4hr)• 4 impact locations / helmet:
• rear, front, left, right• Requirement for Level I, II-A
and II only• No ballistic limit tests (V50)
TCIP Conference and Exposition, November 6-8, 2007
NIJ Standard 0106.01 (1981)NIJ Standard 0106.01 (1981)
Transmitted Force• 1 helmet / test ammunition• tested at ambient conditions• 4 impact locations / helmet:
• rear, front, left, right• Peak linear acceleration
<400g• Correlation with injury
unknown
TCIP Conference and Exposition, November 6-8, 2007
Other Test ProceduresOther Test Procedures• HPW-TP-0401.01B (1995)
• Measure maximum deformation in clay
• Correlation with injury unknown
• STANAG 2920• No requirement for non-
penetrating impacts
• ACH Specifications• Measure maximum
deformation in clay• Correlation with injury
unknown
clay
TCIP Conference and Exposition, November 6-8, 2007
Proposed Test MethodProposed Test Method
• confirm penetration resistance with separate headform
• implement an impact force measurement headform
• based on injury model developed by Bass et al. (2003) using localized skull pressure
• predict risk of skull fracture from dynamic force measurements
• evaluate BABT protection performance of ballistic helmets
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Peak Force (N)
Inju
ry r
isk
50% Risk at 4256 N
TCIP Conference and Exposition, November 6-8, 2007
Penetration HeadformPenetration Headform
TCIP Conference and Exposition, November 6-8, 2007
Impact Force MeasurementImpact Force Measurement
Load Cell Module
Pressure Sensitive Film
TCIP Conference and Exposition, November 6-8, 2007
Parametric StudyParametric Study
• Energy Absorbing (EA) Material• Standoff• Helmet Shell
TCIP Conference and Exposition, November 6-8, 2007
350 375 400 425 450 475
Projectile Velocity (m/s)
Pea
k Im
pac
t F
orc
e
Helmet A
Helmet B
Helmet C
Helmet D
50% risk of skull fracture
Peak Force vs. Impact SpeedPeak Force vs. Impact SpeedTest
SampleDescription Size
Standoff (mm)
Wt(kg)
AD(kg/m2)
A Baseline design, no EA liner matl M L H H
B Baseline design with EA liner matl M M H H
C New lightweight design M L L L
D New lightweight design L H L L
TCIP Conference and Exposition, November 6-8, 2007
Time
Forc
e
Helmet A (405 m/s) Helmet B (398 m/s)
Energy Absorbing LinerEnergy Absorbing Liner
TCIP Conference and Exposition, November 6-8, 2007
OutcomesOutcomes
• Current design & new lightweight helmets can have comparable BABT attenuation
standoff peak impact force
• EA materials peak impact force (load distribution)
TCIP Conference and Exposition, November 6-8, 2007
Standards ActivitiesStandards Activities
• The Canadian Standards Association (CSA) has formed a new CSA Technical Committee to create a National Standard on ballistic helmets (CSA Z613).
• The National Institute of Justice Ballistic Helmet standard is under revision.