© 2009, University of Delaware, all rights reserved© 2009, University of Delaware, all rights reserved

MOTIVATION AND OBJECTIVES PROCESSING OF SOFT LAMINATES

PENETRATION MECHANICS OF SOFT LAMINATES AND FABRICS

K. Ayotte (BME), B. Gama, R. Adkinson (ARL)

University of Delaware . Center for Composite Materials

Penetration mechanics of soft laminates are not well

understood, in fact, there is an insignificant amount of literature

available on this subject.

Penetration mechanics of thick-section composites have been

recently developed following a Quasi-Static Punch Shear Test

(QS-PST) experimental methodology.

The main objective of this research is to use QS-PST

methodology to understand the non-linear penetration damage

mechanisms of soft laminates.

Proven capable of quantifying ballistic damage

mechanisms and energy dissipation in thick-section

composites.

Specimens are tested at different support span

diameter ( Ds) to a constant punch diameter (Dp)

ratios ( SPR = ( Ds / Dp).

The resulting load-displacement data for each

test can be used to calculate the energy absorption

by different energy absorbing damage

mechanisms.

COMPRESSION MOLDING ON A HOT

PRESS Bolts on frame are tightened around

molding plates and frame is placed in

the center of hot press platens.

Platens are heated to 150°F and

the load is set to 145psi.

Once core temperature of laminas

reach 140°F, load is increased to

3000psi and platen temperature to

267°F.

Pressure is maintained until core

temperature reaches 257°F. (Max.

allowed core temp. is 267°F).

QS-PST METHODOLOGY

12”x12” soft lamina sheets are cut to

smaller dimensions.

All laminas are kept in the same

orientation.

Compression molding on a hot press

is used for processing

Soft laminas are sandwiched between

two molding plates.

High temperature films are set

between laminas and molding plates.

Top molding plate is 1”, bottom

molding plate is 0.25” thick.

QS PENETRATION FORCE -

DISPLACEMENTQS PENETRATION DAMAGE

MECHANISMS

SPR = 1.5

SPR = 2.0

SPR = 2.5

SPR = 3.0

25

50

75

100

125

150

175

200

225

250

275

300

0 5 10 15 20 25 30 35 40 45 50 55 600

500

1000

1500

2000

2500

3000

3500

4000

LoadTemperature

Time, Minutes

Te

mp

era

ture

, F

Lo

ad

, p

si

140°F

257°F

3000psi

Inelastic deformation prior to first failure is associated

with the formation of the inelastic shear cone

APPROACH

SPR = 3.0

DAMAGE MECHANISMS AT

DIFFERENT SPRs

platens

Other objectives include (i)

Development of new test methods, & (ii)

Development of new penetration models

for this group of materials.

Processing of soft laminates

Quasi-static penetration testing Different thickness

Different support spans

Damage evaluation

Analysis of experimental data

More fiber pull out and more

shear deformation is observed

with increasing SPRs.

SPR = 1.5

0

1000

2000

3000

4000

5000

6000

7000

8000

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

SPR 3.0SPR 2.5SPR 2.0SPR 1.5

Displacement, , in.

Lo

ad

, P

, lb

f

laminas

Laminate is cooled when

core temperature reaches

257°F.

Laminate is unloaded when

core temp. reaches below

140°F.

© 2009, University of Delaware, all rights reserved© 2009, University of Delaware, all rights reserved

Soft Laminates are manufactured on a hot

press using compression molding.

QS-PST’s are used to produce load

displacement data which is used to investigate

energy dissipation and penetration damage

mechanisms.

Larger SPRs are associated with greater shear

damage and more fiber pull out.

Thicker soft laminates alter the effects of SPR.

Larger SPRs result in greater dissipation of

energy and greater penetration energy.

DAMAGE MECHANISMS – EFFECT OF

LAMINATE THICKNESSDAMAGE MECHANISMS AT

DIFFERENT DISPLACEMENTS

PENETRATION MECHANICS OF SOFT LAMINATES AND FABRICS(Continued)

DAMAGE MECHANISMS AT

DIFFERENT DISPLACEMENTSSUMMARY

ACKNOWLEDGEMENTS

Funding for this work is provided by ARL-CMR

MIPR (Soft Laminate).

A load stop test is used to investigate damage as a

function of displacement.

The test is stopped at different displacement levels

signifying different damage mechanisms.

1

2

3

QUASI-STATIC ENERGY

DISSIPATION

At 0.40” displacement, all fibers

remain intact.

At 0.42”, shear cutting of a couple

layers of fiber is observed.

At 0.46”, shear cutting through

half of layers.

0

1000

2000

3000

4000

5000

6000

7000

8000

0 0.1 0.2 0.3 0.4 0.5 0.6

y = 5000xy = 10000xy = 15000xy = 33000xy = 56100xSPR = 1.5

K = 5000 lbf/in

K = 10000 lbf/in

K = 15000 lbf/in

K = 33000 lbf/in

K = 56100 lbf/in

Displacement, , in.

Lo

ad

, P

, lb

f

QUASI-STATIC ENERGY

DISSIPATION

/

0/

PK

2 / 2IEE P K

/

TE Pd

PE T IEE E E

20 Layers 40 Layers 60 Layers

Effects of SPR start

to diminish as the

number of layers of

lamina increase.

More peaks and

valleys are seen in

thicker laminates.

0

1000

2000

3000

4000

5000

6000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Displacement, , in

Lo

ad

, P

, lb

f

1

2 3

1 –

The

“knee”

before the

first local

peak

2 –

After first

failure

3 –

After

second

failure0

K – Stiffness, lbf/in.

EIE – Inelastic energy, lbf-in.

ET – Total energy, lbf-in.

EPE –Penetration

Energy, lbf-in.

SPR = 1.5 SPR = 2.0

SPR = 2.5 SPR = 3.0

NEW TEST METHODOLOGIES

The direct impact punch shear test (DI-PST) will be

used to investigate failure mechanisms under high strain

rates.

The dominant transverse punch shear damage

mechanisms of hard composites are almost absent in

quasi-static punch shear tests, so DI-PST will be used.

A striker bar is shot out of a pressurized tank at high

velocity and strikes the punch through the specimen.

Waves transmit through the incident bar and resulting

data from a strain gage is used to determine dynamic

compression force-displacement behavior of different

materials

0

2000

4000

6000

8000

10000

12000

14000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

604020 Layers

Displacement, , in

Lo

ad

, P

, lb

f

0

500

1000

1500

2000

2500

3000

3500

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Penetration EnergyInelastic EnergyTotal Energy

Displacement, , in

En

erg

y,

E,

lbf-

in

0

500

1000

1500

2000

2500

3000

3500

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Penetration EnergyInelastic EnergyTotal Energy

Displacement, , in

En

erg

y,

E,

lbf-

in

0

500

1000

1500

2000

2500

3000

3500

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Penetration EnergyInelastic EnergyTotal Energy

Displacement, , in

En

erg

y,

E,

lbf-

in

0

500

1000

1500

2000

2500

3000

3500

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Penetration EnergyInelastic EnergyTotal Energy

Displacement, , in

En

erg

y,

E,

lbf-

in