Ballistic HelmetBallistic HelmetStandardStandard

Technologies for Critical Incident Preparedness Conference and Exposition

San 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 Reviewmid 90’ DRDC Valcartier initiated study on backface

impact force / deformation1997 NATO BABT TG0012000 Natick Soldier Center: developed skull fracture

injury function (UVa)2002 TSWG funded development of ballistic helmet

test method2005 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 inj

ury

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 ri

sk

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)

Peak

Impa

ct F

orce

Helmet AHelmet BHelmet CHelmet D

50% risk of skull fracture

Peak Force vs. Impact SpeedPeak Force vs. Impact SpeedTest

Sample Description 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.