Arun Shukla, Nate GardnerDynamic Photo Mechanics Laboratory , Dept. of Mechanical, Industrial and Systems Engineering

The University of Rhode Island, Kingston RI 02881Shuklaa @egr.uri.edu

The dynamic behavior of various sandwichcomposites made of E-Glass Vinyl-Ester andCorecell A-series foam have been studied using ashock tube apparatus. For the polyureainvestigation, the foam core was monotonicallygraded based on increasing wave impedance, andthe influence of the polyurea location on theoverall dynamic behavior was studied. For theCoreShell Rubber (CSR) vs Non-CSR toughenedresin composite investigation, the core washomogeneous, and the influence of the coreshellrubber nano-particles on the overall dynamicbehavior was studied. A high-speed side-viewcamera, along with a high-speed back-view 3-DDigital Image Correlation (DIC) system was utilizedto capture the real timedeformation process aswell as mechanisms of failure. Post mortemanalysis was also carried out to evaluate the overallblast performance. Results will help in designingnew and more efficient blast mitigating materialsand structures.

With an increased threat of damage to civilian anddefense structures in the form of blast loading therehas arisen a need to replace conventional structuralmaterials with improved blast resistant material aswell as generate new ideas to mitigate blast over-pressure.

This material is based upon work supported by the U.S. Department of Homeland Security under Award Number 2008-ST-061-ED0001. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied of the U.S. Department of Homeland Security.

N. Gardner, E. Wang, P. Kumar and A. Shukla, “Blast Mitigation in aSandwich Composite using Graded Core with Polyurea interlayer”Experimental Mechanics, Accepted for Publication (2011) E. Wang, N Gardner and A. Shukla, “The blast resistance of sandwich

composites with stepwise graded cores”, International Journal of Solidand Structures, 46, 3492-3502, 2009. E. Wang, N. Gardner and A. Shukla, “Experimental study on the

performance of sandwich composites with stepwise graded coressubjected to a shock wave loading”, SEM Annual Conference andExposition on Experimental and Applied Mechanics, Albuquerque, NewMexico , June 1-4, 2009. N. Gardner, “Blast performance of sandwich composites with discretely

layered core”, SEM Annual Conference and Exposition on Experimentaland Applied Mechanics, Student Paper Competition, Albuquerque, NewMexico , June 1-4, 2009. N. Gardner and A. Shukla, “The Blast Response of Sandwich Composites

with a Functionally Graded Core”, SEM Annual Conference and Exposition,Indianapolis, Indiana, June 7-10, 2010. N. Gardner and A. Shukla, “The Blast Response of Sandwich Composites

With a Functionally Graded Core and Polyurea Interlayer”, SEM AnnualConference and Exposition, Indianapolis, Indiana, June 7-10, 2010. N. Gardner and A. Shukla, “The Blast Resistance of Sandwich Composites

with a Functionally Graded Core and Polyurea Interlayer”, IMPLAST 2010,SEM Fall Conference, Providence, October 12-14, 2010.

Novel Sandwich Composite Structures for Blast Mitigation

Technical ApproachAbstract

Relevance

Accomplishments Through Current Year

Future Work

Publications Acknowledging DHS SupportOpportunities for Transition to

Customer

Experimental Set-up and Procedure: Materials and Specimens:

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Configuration 1 Configuration 2

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Results:

Blast loading on civilian structures

Blast attack on USS Cole Blast attack on Army structures

Consulting with Industry:

1. TPI Composites, Warren, RI2. Specialty Products Inc.(SPI), Lakewood, Washington3. Gurit SP Technology, Quebec, Canada

New types of sandwich structures were designed andfabricated to withstand blast loadings and mitigateblast overpressures. Technical collaboration with TPIComposites, Specialty Products Inc., and Gurit SPTechnology will help in fascilitating samplepreparation. This effort also aligns with the mission ofDHS to transition technology and allow for a unifiedeffort to protect our homeland.

Acknowledgements

The authors kindly acknowledge the financial supportprovided by Department of Homeland Security (DHS) underCooperative Agreement No. 2008-ST-061-ED0002, as well asthe Office of Naval Research (ONR) under Grant No. N00014-04-1-0268. Authors thank Gurit SP Technology and SpecialtyProducts Incorporated (SPI) for providing the material as wellas Dr. Stephen Nolet and TPI Composites for providing thefacility for creating the composites used in this study.

1. The effect of equivalent core layer mass vs. equivalent corelayer thickness in the blast response of sandwich structures

A comprehensive series of shock tube experiments wereconducted on sandwich panels consisting of compositefacesheets and energy absorbing core materials in order toevaluate the overall blast response and mitigation capabilities

Major Results

1. Polyurea Investigation: The application of polyurea behindfoam core and in front of back facesheet (configuration 2)allows for stepwise compresison of core, reducing deflections,in-plane strains, back face velocities and overall damage

2. CSR vs Non-CSR Toughened Composite Investigation: Theaddition of nano-scale Coreshell Rubber (CSR) particles to theresin system of the sandwich structures, aids in dispersing theinitial impulse of the shock wave, thus reducing deflections,in-plane strains, and back face velocites and overall damage

Previously, the main focus of research in this areahas been on the numerical and theoretical behaviorof functionally graded materials. Experimental workon the dynamic response of composites withpolyurea, as well as steel plates with polyurea hasbeen investigated, but there has been no researchregarding the dynamic response of sandwichcomposites with polyurea interlayer. Also, theaddition of core shell rubber (CSR) to sandwichstructures and their influence on blast loading is arelativley new application and investigation.Previously, only the impact response of core shellrubber (CSR) toughened composites has beenstudied.

The Shock Tube

Schematic of Shock Tube

Detailed Dimensions of the Muzzle

Real Pattern

Back View 3-D DIC System

Side View Camera

Specimen

Shock Tube

High-speed photography set-up

Core:

Co-Polymer I designed for

impact resistance

Shell:

Co-Polymer II designed to be

compatible with thermosetting

resinsMicroscopic View of Coreshell Rubber[www.kaneka.com]

(a) Schematic (b) Real SecimenSpecimen Configuration

(a) Non-CSR (b) CSRFacehseet of Sandwich Structure

Core cracking

DelaminationCore Compression

Core cracking

DelaminationCore Compression

(a) Non-CSR (b) CSRPost-mortem Images of CSR and Non-CSR

Toughened Sandwich Composites

Core Compression

Delamination

Core cracking

Complete Core CollapseCore Compression

Core cracking

Delamination

Core Compression

Delamination

Core cracking

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1.0 MPa 1.5 MPa

Post-mortem Images of Both Configurations

Indentation failure

First LayerCompression

Core CrackingBegins

SkinDelamination

Core Cracking

Indentation failure

SkinDelamination

Core CrackingBegins

Core Cracking

First LayerCompression

Configuration 1

Configuration 2

High Speed Images of Both Configurations

In-plane strain for Both Configurations

Out-of-plane velocity of CSR and Non-CSR

Toughened Sandwich Composites

Indentation failure

Core Cracking

Core LayerDelamination

SkinDelamination

Indentation failure

Core Cracking Core Layer

Delamination

No

n-C

SRC

SR

High Speed Images of CSR and Non-CSR Toughened Sandwich Composites

0 μs 100 μs 400 μs 700 μs 1000 μs 1600 μs

0 μs 100 μs 400 μs 700 μs 1000 μs 1600 μs

Full-field out-of-plane Deflection

No

n-C

SRC

SR

100 μs 400 μs 700 μs 1000 μs 1600 μs

100 μs 400 μs 700 μs 1000 μs 1600 μs

Full-field in-plane Strain

No

n-C

SRC

SR

100 μs 400 μs 700 μs 1000 μs 1600 μs

100 μs 400 μs 700 μs 1000 μs 1600 μs

0 μs 150 μs 400 μs 650 μs 1150 μs 1800 μs

0 μs 150 μs 400 μs 550 μs 1150 μs 1800 μs

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Full-field out-of-plane Deflection

150 μs 400 μs 550 μs 1150 μs 1800 μs

150 μs 400 μs 650 μs 1150 μs 1800 μs

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Full-field out-of-plane Velocity

150 μs 400 μs 550 μs 1150 μs 1800 μs

150 μs 400 μs 650 μs 1150 μs 1800 μs

Incident and Reflected pressure profiles

Incident Pulse

Reflected Pulse