1

Blast Mitigation Effort

DHS Summit Meeting March 2010

Arun Shukla

TEAM

University of Rhode IslandUniversity of Illinois Urbana-ChampaignPurdue UniversityCalifornia Institute of Technology

Northeastern UniversityMissouri Science & TechnologyWashington State University

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Introduction

Blast Mitigation

Dampening ofBlast Overpressure

Absorption and Reflection of Energy

Post Blast Performance

Water-MistDesigned Barriers…

Soft MatterComposite MaterialsSandwich StructuresFunctional Graded MaterialsCoated Materials…

Fire and Structural CollapseSelf Healing Materials…

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Response of Sandwich Composite Panels to Shock Loading

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Sandwich Composites

These are materials consisting of two face sheets sandwiching a core material.

Advantages:High strength and stiffness per unit weightGood thermal insulationHigh energy absorption

Carbon Fiber Vinyl Ester Composite — Balsa Wood Sandwich

E-Glass Vinyl Ester Composite — Corecell Foam Sandwich

5

Shock Tube

AdvantagesHighly controlled and repeatable testing conditions

Wave fronts with high velocity and pressure

Plane wave fronts

Diaphragm

Driver Section

Driven Section

Muzzle

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Experimental Setup

Length: 10 inWidth : 4 in

Inter-frame time : 50-200 µsExposure time : 500-1000ns

Span: 6 in Diameter of loading area: 3 in

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Real Time Observation

E-Glass Vinyl Ester Composite — Corecell Foam Sandwich under blast load

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DIC Experimental Setup

Real Pattern

DIC System

Side View Camera

Specimen

Shock Tube

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Shear Strains in the Core 2-D and 3-D DIC System

2-D DIC 3-D DIC

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3D-Deflections

PU Front

600

mic

rose

cond

s

PU Back

1800

mic

rose

cond

s

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Energy Calculation

Incident process: Reflected process:

u1, p1, c1 u0, p0, c0

U+

Spec

imen

u1, p1, c1 u2, p2, c2

U-

Spec

imen

Incident and Remaining Energy Calculations:

Remaining Energy: energy stored in the gas located behind the reflected shock front

Incident Energy: energy stored in the impinging gas

( ) cross-section gas particlepressure

area speeddt

⎡ ⎤⎛ ⎞ ⎛ ⎞× ×⎢ ⎥⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠⎣ ⎦

∫=E

( )

( )( ) ( )( ) ( )( )( ) ( )( ) ( )

22 22 1

1 1

22 2 20 1 0 0 0

22 2 21 1 2 1 1

1

1 1

1 1

p u Up c

U u u u U u c

U u u u U u c

μ μ

μ μ

μ μ

+

+ +

− −

⎛ ⎞+= + −⎜ ⎟⎝ ⎠

− − − − − = −

− + − − + = −

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Specimen Configurations(Monotonically Increasing Wave Impedance)

Total length:254 mm (10 in)

Total width: 101.6 mm (4 in)

Total thickness: 48 mm (1.9 in)

Face sheet thickness: 5 mm (0.2 in)

Con

figur

atio

nsSp

ecim

ens

Specimen Dimensions:

Gradation Average Areal Density (kg/m2)

1 Layer 19.12

2 Layer 18.43

3 Layer 19.02

4 Layer 20.07

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Specimens and Configurations

Dragonshield HT Properties

Average Areal Density: 26 kg/m2

Con

figur

atio

nsSp

ecim

ens

PU Front PU Back

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High Speed Video

PU Front (Sample 3) PU Back (Sample 4)

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Post-Mortem ImagesPU

Fro

ntPU

Bac

k

Front face sheet (blast side) Foam core Back face sheet

Core Compression

Core cracking

Delamination

Core Compression

Delamination

Core cracking

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High Speed Video (10 plys)

PU Back(Sample 1) PU Front (Sample 3)

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The Effect of Low and High Velocity Impact Damage on Blast Performance

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Low Velocity Impact Experiment

Impact Velocity ≈ 4.7 m/sImpact Mass ≈ 26.1 kgImpact Energy ≈ 300 J

0

5

10

15

20

25

30

35

0 5 10 15

Load

(kN

)

Time (ms)

6 “

Simple Supports

1” Hemispherical Impactor

SandwichSpecimen

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Typical Low VelocityImpact Damage

Loading area of shock tube

Low velocity impact damage

Face sheet

Core

Face sheet/CoreDe-bonding

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Typical High VelocityImpact Damage

25 mm

50 mm

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Post Blast Images of Pre DamagedSandwich Composites

Large core cracking

De-bonding

Resin columnprotruding

Specimen with HighVelocity Impact Damage

Specimen with LowVelocity Impact Damage

Impact Type: High Velocity (920 m/s)Number of Impacts: 5Impact Mass : 0.01KgTotal impact Energy Absorbed: ≈ 2108J

Impact Type: Low Velocity (4.7 m/s)Number of Impacts: 3Impact Mass : 26.21 kgTotal impact Energy Absorbed: ≈ 760J

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Keynote SpeakersDr. Gerald Nurick, University of Capetown, South AfricaDr. Mary Ellen Hynes, Department of Homeland Security, USADr. Ravinder Chona, Air Force Research Laboratories, USADr. William G. Proud, Cavendish Laboratories, Cambridge, UKDr. Yapa D.S. Rajapakse, Office of Naval Research, USA

IMPLAST 2010

Workshop on Blast Mitigation

Renaissance Providence Hotel

SEM FALL CONFERENCE

12-14 October 2010