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© 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