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Composite Structures and Nano-Engineering Research

The University of Mississippi

Blast and Impact Resistant Composite Structures for Navy Ships


University of Mississippi

OBJECTIVE AND SCOPE OF RESEARCH

Light weight, fast, stealthy ships are required for the US Navy littoral operations. The

currently approved series of ships, the DD(X), has stringent requirements for reduced

topside weight as well as fire/smoke toxicity.

Need for reducing life cycle costs, and the ability to incorporate multi-functionality,

including blast, shock and impact resistant features lead towards the use of affordable

composite materials and sandwich structures.

Scope of our research includes: low-cost fire-resistant exfoliated graphite nano platelet

reinforced glass/carbon polymeric based composites with fly ash and 3-D fiber

reinforced foams; investigating their response to low-velocity impact, ballistic, shock

and blast loads; dynamic mechanical analysis for modulus, damping, creep and stress

relaxation; developing constitutive models and high-performance scalable computing

based modeling and simulations; accelerated testing for long-term durability; and their

radar-absorbing and EM-shielding characteristics for improved stealth and safety.

MATERIALS

FIBERS:

E-Glass,

T700 graphite,

HPG (Owens Corning)

CORES:

Tycor, Balsa, PVC,

Eco-Core

MATRICES:

Vinyl ester, Phenolic

NANO:

xGnP graphite platelet,

Cloisite 30B nanoclay,

MWCNT

TESTING

BLAST:

Blast load simulator

SHOCK:

Shock tube

IMPACT:

- Low velocity drop weight

- High strain Hopkinson Bar

- Ballistic projectile

DMA (Dynamic Mechanical

Analysis)

LONG TERM DURABILITY

MULTI-FUNCTIONAL

- EM Interference

- Radar Shielding

- Fire Resistance

ANALYSIS

- Modeling & Simulations

(AUTODYN, EPIC)

- Particle Dynamics

- Shock Models

SANDWICH STRUCTURES

- E-glass / Tycor 3-D foam core

- E-glass / Balsa wood core

- T700 Graphite / PVC foam core

NANO FILMS / COATINGS

- Graphite platelet films / coatings

- Elastomeric coatings

BLAST AND IMPACT RESISTANT COMPOSITE STRUCTURES FOR NAVY SHIPS



RESEARCH PARTNERS

The University of Mississippi (UM), Michigan State University (MSU), and University of

New Orleans (UNO), supported by the US Army Corps Engineer Research and

Development Center (ERDC) are utilizing their research strengths in modeling, analysis,

fabrication and testing of affordable blast, shock and impact resistant nanoparticle

reinforced composite structures for the new generation navy ships.

University of Alabama-Birmingham (UAB) is fabricating the large VARTM sandwich

composite panels and performing quasi-static, fire and ballistic tests.

North Carolina A&T State University (NC AT) is providing their patented low-cost fire

resistant fly ash based Eco-Core foams.

Northrop Grumman Ship Building (NGSB), Gulfport, MS is advising and facilitating UM on

these research efforts.

WebCore Technologies, Miamisburg, OH is providing their patented TYCOR® foam cores

for blast, shock and impact resistant sandwich panels.



SANDWICH COMPOSITES

Sandwich composites with balsa and foam cores are presently being featured in a

number of navy applications such as surface ship deck structures, radar masts and

boat hulls. In the present work, some new and emerging cores have been explored in

sandwich construction. Different core types that have been considered include:

Balsa wood, a traditional core material, used in present generation ship structures. Balsa is

a natural material, prone to local variation in properties due to cell size and cell thickness

variations;

Polyvinyl chloride (PVC) foam core is also used in present generation ship structures for

radar mast enclosures and boat hulls;

Eco-Core is an emerging fire resistant sandwich core. Fire damage in ship structures is of

significant concern. The burn-through resistance and heat insulation characteristics of Eco-

core makes it an attractive fire resistant core.

Tycor (TYCOR® from WebCore Technologies), an engineered three-dimensional fiber

reinforced damage tolerant core for sandwich structures, has the potential to provide

improved blast and ballistic resistance. In this core, glass fiber is reinforced through the

thickness of closed cell foam sheets to produce a web and truss structure.



TYCOR® 3-D STITCHED FOAM

WEBCORE TECHNOLOGIES



BLAST RESISTANCE OF SANDWICH COMPOSITES

Trial blast tests, simulating approximate threat levels of 2000 to 27,000 lbs TNT at about

150 feet, were conducted at the ERDC - Blast Load Simulator (BLS) facility.



One 4’ x 4’ E-glass/Tycor panel, with all-around

bolted b.c. was subjected to about 80 psi peak

pressure.

Panel was not breached and there are no visible

signs of damage.

Foam used for filling gaps between the frame and

target vessel blew out. Deflection gage disengaged

and laser over heated during the experiment



E-GLASS / TYCOR SANDWICH PANEL (fixed-free) - BLAST TEST



E-GLASS / TYCOR SANDWICH PANEL (fixed-free) - AFTER BLAST TEST



One 64” x 34” E-glass/Balsa core panel was subjected to about 60 psi peak pressure

with different holding fixture.

Panel slid through the supports and was completely damaged, with E-glass face skin on blast

side shearing into two halves at the middle.

Instrumentation, data acquisition and specimen clamping issues are being resolved for future

full-scale blast experiments.

Sandwich composite panels, bolted at top/bottom

and two-sides free, undergoing blast tests of 16

to 18 psi peak pressure and 200 psi-ms impulse

(equivalent to ~ 2000 lbs of TNT at 140 feet).

Panels underwent 0.5 to 1.5 inches of mid-point

deflection, with no visible signs of damage.

BLAST TESTS ON SANDWICH COMPOSITE PANELS

P4 (initial pressure)

P5high-pressure

chamber

low-pressure

chamberpiston

P1(initial pressure)

intermediate-pressure

chamber with 1st diaphragm2nd diaphragm

P6 dump-tank

Blast tube

P4 (initial pressure)

P5high-pressure

chamber

low-pressure

chamberpiston

P1(initial pressure)

intermediate-pressure

chamber with 1st diaphragm2nd diaphragm

P6 dump-tank

Blast tube

SHOCK TESTS ON SANDWICH BEAM SPECIMENS

Shock tests were performed (at Michigan State University) on sandwich beam specimens

held under simply supported conditions and subjected to ~1350 psi peak pressure.

Innovative 20-pin finger sensor was used for measuring the deformations when fingers

contacted backside of specimen.

SHOCK RESPONSE OF SANDWICH BEAM SPECIMENS

CONSTITUTIVE MODELING AND SIMULATIONS

ANSYS AUTODYN (an explicit hydrocode that uses finite difference, finite volume, and

finite element techniques to solve wide variety of non-linear dynamic problems in solids,

fluids, gases, and their interactions) was used to model and analyze sandwich composite

beams under shock loading.

Experimental AUTODYN Simulation

PVC-Core

Balsa-Core

TYCOR-Core

Failure shapes, obtained experimentally and numerically, for

sandwich composite beams under shock loading.

TENSION AND COMPRESSION

HOPKINSON BARS

SHOCK TUBE

EXPERIMENTAL FACILITIES ESTABLISHED

AT UNIVERSITY OF MISSISSIPPI

Shock tube (with piston attachment) for

generating blast pressure wave forms up

to 15 Kpsi (100 MPa) and 50 milli sec

duration at 1000 ft/sec (300 m/sec)

velocity.

Split-Hopkinson Pressure Bars (SHPB)

for the high-strain rate evaluation of

nano-reinforced specimens, foams and

sandwich composites, in both tension

and compression.

Experimental blast response and quasi-static material property data were generated for

E-glass and carbon facesheet sandwich composite panels with balsa, PVC foam and

TYCOR® cores.

The Pressure vs Impulse (P-I) curve methodology that was developed to represent

estimated damage levels in civil infrastructure components subjected to blast loadings,

has been adapted for analyzing these sandwich composite panels.

P-I curve methodology enables the generation of a database of performance envelopes

for sandwich composite panels with a variety of skin and core material combinations

under various blast and shock loading scenarios.

Results show good correspondence between model predictions and experimental data

for the performance evaluation of sandwich composite panel configurations that were

analyzed.

COMPUTATIONAL SIMULATION AND ANALYSIS

The P-I (Pressure-Impulse) diagram mathematically relates a specific damage level to a

combination of blast pressure and impulse imposed on a particular structural element and

allows reduced order modeling of the sandwich composite panel systems.

P-I curves are also known as iso-damage curves with each curve representing a certain

response level such as mid-span deflection or rotation at supports, etc.

In a particular threat scenario, the pressure and impulse acting on a structure can be

determined by using scaling laws based on the distance of the structure from the blast

source.

Knowing the distribution of pressure and impulse due to a specific blast scenario, the

damage to individual components in terms of ductility demand can be determined from

the P-I chart, and can also be further mapped onto a structure consisting of many

such components.

P-I CURVE METHODOLOGY

Ro

yo Equivalent SDOF System

Force-Deflection Curve

P-I Curves

y/ yo

Composite Panel

PROCEDURE FOR GENERATING P-I CURVES NUMERICALLY

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