The Effects of PMMA on Ballistic Impact Performance of 

Hybrid Hard/Ductile All-Plastic- and Glass-Plastic-Based 

Composites 

by Alex J. Hsieh, Daniel DeSchepper, Paul Moy, Peter G. Dehmer, 

and John W. Song 

ARL-TR-3155 February 2004 

Approved for public release; distribution is unlimited. 
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Army Research Laboratory 

Aberdeen Proving Ground, MD 21005-5069 

ARL-TR-3155 February 2004 

The Effects of PMMA on Ballistic Impact Performance of 

Hybrid Hard/Ductile All-Plastic- and Glass-Plastic-Based 

Composites 

Alex J. Hsieh, Daniel DeSchepper, Paul Moy, and Peter G. Dehmer 

Weapons and Materials Research Directorate, ARL 

John W. Song 

Natick Soldier Center 

Approved for public release; distribution is unlimited. 
ii

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The Effects of PMMA on Ballistic Impact Performance of Hybrid Hard/Ductile 

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14. ABSTRACT 

The U.S. Army Research Laboratory is focusing on utilizing the materials-by-design strategy in the development of transparent armor 

systems to achieve lightweight, mobility, enhanced survivability, and lower life cycle costs for the soldiers and ground vehicle 

protection. The focus of this research is to identify the material parameters that are critical for the ballistic performance of hybrid 

hard/ductile laminate systems. We evaluated the role of poly(methyl methacrylate), (PMMA), on the impact response of composites 

consisting of PMMA and polycarbonate, (PC), as well as on the PC-Glass-PMMA-PC laminates against the .22-cal. fragment 

simulator projectile and the 124-gr 9-mm projectile. Increasing the thickness of PMMA improved the overall impact capability of 

these laminates. Incorporation of PMMA as an intermediate ply between the glass and ductile PC appeared to be a very effective

approach for the design of glass-plastic laminates. We attributed this observation to the high strain-rate sensitivity characteristics of 

the monolithic PMMA. Preliminary results obtained from the 9-mm projectile testing clearly indicated that the PMMA-based allplastic laminates maintained a significant amount of residual visibility after impact, which was critical for transparent armor

applications. 

15. SUBJECT TERMS

ballistic measurements, poly(methyl methacrylate), PMMA, polycarbonate, PC, PMMA-PC laminates, glass-plastic laminates 

16. SECURITY CLASSIFICATION OF: 

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Alex Hsieh 

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410-306-0698 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18
iii

Contents 

List of Figures iv

List of Tables v

Acknowledgments vi

1. Introduction 1

2. Experimental 2

2.1 Target Materials ..............................................................................................................2 

2.2 Ballistic Testing...............................................................................................................3 

2.3 Compression Measurements............................................................................................4 

3. Results and Discussion 5

3.1 PC-PMMA-PC vs. PC-PC-PC Laminates.......................................................................5 

3.2 Effect of PMMA Plate Thickness ...................................................................................7 

3.3 Rate-Dependent Ballistic Response of PMMA...............................................................7 

3.4 Compression Measurements of Monolithic PMMA and PC ..........................................9 

3.5 PC-Glass-PMMA-PC Laminates ..................................................................................11 

3.6 Ballistic Measurements Against the 9-mm Projectile ...................................................14 

4. Conclusions 16

5. References 17

Distribution List 18
iv

List of Figures 

Figure 1. Pictures of .22-cal. FSP (left) and 124-gr, 9-mm projectile (right).................................4 

Figure 2. V50 values obtained for the PC-PMMA-PC and PC-PC-PC laminates against the 

.22-cal. FSP impact....................................................................................................................5 

Figure 3. Typical fracture pattern of the PC-PMMA-PC laminate after impact with the .22-

cal. FSP. .....................................................................................................................................6 

Figure 4. Typical fracture pattern of the PC-PC-PC laminate after impact with the .22-cal. 

FSP.............................................................................................................................................6 

Figure 5. Typical conoid fracture pattern observed in the exit side of the PC-PMMA-PC 

laminate after impact with the .22-cal. FSP...............................................................................7 

Figure 6. V50 values obtained for the PMMA-Sim PU laminates against the .22-cal. FSP 

impact.........................................................................................................................................8 

Figure 7. Plot of V50 vs. areal density for the PC-PMMA-PC, PMMA-Sim 2003 PU, and 

PMMA-PC laminates against the .22-cal. FSP impact..............................................................8 

Figure 8. Plot of V50 vs. nominal plate thickness of monolithic PMMA and PC against the 

.22-cal. FSP impact....................................................................................................................9 

Figure 9. Brittle mode cracking compared to localized deformation observed in the 6-mm 

thick monolithic PMMA after impact with the .22-cal. FSP at a velocity of (a) 173 m/s 

and (b) 1004 m/s, respectively.................................................................................................10 

Figure 10. Plots of ballistic energy values as a function of striking velocity obtained for the 

monolithic PMMA of various target thicknesses against the .22-cal. FSP impact; inserts 

show the corresponding mode of impact-induced failure; solid lines are the second-order 

polynomial curve fit for the corresponding data......................................................................10 

Figure 11. Plots of stress vs. strain data obtained from the constant-strain rate compression 

measurements at 0.001/s and 1/s for the monolithic PMMA and PC......................................11 

Figure 12. Comparison of the apparent compressive yield strength of PC and PMMA with 

respect to the strain rate. ..........................................................................................................12 

Figure 13. Plot of V50 vs. areal density data for the PC-Glass-PMMA-PC laminates (listed in 

table 4) against the .22-cal. FSP impact...................................................................................13 

Figure 14. A combined plot of V50 vs. areal density data for the all-plastic laminates (figure 

7) and PC-Glass-PMMA-PC laminates (figure 13) against the .22-cal. FSP impact; solid 

lines are the linear curve fit for the corresponding data...........................................................13 

Figure 15. PC-PMMA-PC laminate after impact with the 9-mm projectile at 480 m/s. ..............14 

Figure 16. PC-PMMA-PC laminate after impact with the 9-mm projectile at 390 m/s. ..............15 

Figure 17. PC-PC-PC laminate after impact with the 9-mm projectile at 399 m/s. .....................15 

Figure 18. Comparison of the extent of residual visibility seen in the PC-PMMA-PC 

laminate (left) and PC-Glass-PMMA-PC laminate (right) after the 9-mm projectile 

impact.......................................................................................................................................16 
v

List of Tables 

Table 1. Target configuration and areal density of plastic-based laminates obtained from GE 

Polymershapes. ..........................................................................................................................2 

Table 2. Target configuration and areal density of plastic-based laminates obtained from 

Protech Armor Products.............................................................................................................2 

Table 3. Target configuration and areal density of PMMA-Sim polyurethane laminates..............2 

Table 4. Target configuration and areal density of Pyrex glass-plastic laminates..........................3 

Table 5. Target configuration and areal density of sodalime glass-plastic laminates. ...................3 

Table 6. Values of apparent compressive yield stress as a function of constant strain rate for 

the monolithic PMMA and PC. ...............................................................................................12 

Table 7. Areal density of PC-PMMA-PC and PC-Glass-PMMA-PC laminates and their 

corresponding V50 values against the 9-mm projectile............................................................14 
vi

Acknowledgments 

The authors would like to thank Russell Prather and Ricky Kane of the U.S. Army Research 

Laboratory (ARL) for performing the ballistic testing and data acquisition, Dr. Walter Zukas at 

the Natick Soldier Center (NSC) for review and comments, Randy Natches at NSC for 

fabricating the compression test specimens, and Thomas Haines of GE Polymershapes for 

providing the PC (polycarbonate)-PMMA poly(methyl methacrylate)-PC and PC-PC-PC 

laminate samples. 
1

1. Introduction 

Recent events in Operation Iraqi Freedom reveal a critical demand for lightweight transparent 

armor with enhanced survivability against emerging threats. Thus, the U.S. Army Research 

Laboratory (ARL) is engaged in a joint effort with partners to further develop and optimize novel 

hybrid hard/ductile composites with capabilities of defeating a wider range of ballistic threats at 

higher mass efficiencies (i.e., reduced weights and thicknesses) and lower costs (1). 

Transparent armor materials are commercially available and have been applied in a variety of 

military and civilian systems and equipment including face shields, goggles, vehicle vision 

blocks, windshields and windows, blast shields, and aircraft canopies. However, almost all 

reports that are available in the literature do not address whether material characteristics such as 

strain-rate sensitivity of the monolithic components is critical to the overall ballistic performance 

of these laminated armor systems. This research focuses on the transparent polymeric materials 

primarily used for personnel and ground vehicle protection. Earlier test results revealed that poly 

(methyl methacrylate) (PMMA) plays an important role in the ballistic optimization of laminated 

structures consisting of PMMA and polycarbonate (PC) (2, 3). PC is ductile in nature and serves 

as backing plates to mitigate spall-induced damage as well as to provide the desired structural 

support. The monolithic PMMA, albeit brittle upon the tensile deformation, exhibits better 

impact performance against the .22-cal. fragment simulator projectile (FSP) than PC at 

equivalent plate thickness ~12 mm or higher. These experimental findings provide the basis for 

materials selection, such as using thin monolith of ductile polymers for eye protection systems 

like goggles and visors, for optimization of layer configuration of composites utilized as ballistic 

shields for the Explosive Ordnance Disposal (EOD), and for potential vehicle applications. 

One of the objectives of this research is to determine whether the unique impact behavior of 

PMMA is primarily geometry-dependent or if it is an intrinsic characteristic of the material. In 

this study, we have carried out ballistic measurements over a wide range of impact velocities 

including those well above the ballistic limits and determined the impact response of PMMA 

with respect to the loading conditions. We also evaluated the effect of PMMA plate thickness on 

the overall ballistic performance of the selected PC-PMMA-PC, PMMA-PC, PMMA-Simula 

(SIM) 2003 polyurethane, and glass-plastic systems. The work on glass-plastic laminates serves 

as the feasibility study to determine the effectiveness of integrating PMMA in the design and 

ballistic optimization of ceramic-plastic laminates-based armor. The preliminary test results 

obtained from the 9-mm projectile impact measurements for the selected laminate systems are 

also included for discussion. 
2

2. Experimental 

2.1 Target Materials 

The selected laminates consisting of various layer configurations of monolithic plates of Lexan*

polycarbonate, and Plexiglas G† poly (methyl methacrylate), were prepared and obtained either 

from Protech Armor Products (Pittsfield, MA) or from GE Polymershapes (Allentown, PA). 

These laminates, with an overall plate thickness close to those of the EOD shields of interest, 

were selected as model materials systems for this study. Table 1 lists the plate configuration and 

areal density of the PC-PMMA-PC and PC-PC-PC laminates from GE Polymershapes, and 

table 2 lists the PMMA-PC laminates from the Protech Armor Products. The selected 

PMMA-Sim PU laminates listed in table 3, consisting of PMMA as front plate and Sim 2003 

polyurethane (from Simula Technologies, Inc., Phoenix, AZ) as back plate, were also included 

for comparison. 

Table 1. Target configuration and areal density of plastic-based laminates obtained from GE 

Polymershapes. 

Target Type Laminate Configuration Areal Density 

(lb/ft2

) 

PC-PMMA-PC 3-mm PC/12-mm PMMAa/3-mm PC 4.68 

PC-PC-PC 3-mm PC/12-mm PC/3-mm PC 4.85 a

 Nominal thickness of the cast PMMA plate. 

Table 2. Target configuration and areal density of plastic-based laminates obtained from 

Protech Armor Products. 

Target Type Laminate Configuration Areal Density 

(lb/ft2) 

PMMA-PC-1 12-mm PMMAa/3-mm PC 3.81 

PMMA-PC-2 9-mm PMMAa/6-mm PC 3.82 

PMMA-PC-3 12-mm PMMAa/6-mm PC 4.37 

PMMA-PC-4 18-mm PMMAa/3-mm PC 5.25 

PMMA-PC-5 18-mm PMMAa/6-mm PC 5.59 a

 Nominal thickness of the cast PMMA plate. 

Table 3. Target configuration and areal density of PMMA-Sim polyurethane laminates. 

Target Type Laminate Configuration Areal Density 

(lb/ft2

) 

PMMA-Sim 2003 PU-1 6-mm PMMAa/6-mm Sim 2003 PU 3.18 

PMMA-Sim 2003 PU-2 9-mm PMMAa/6-mm Sim 2003 PU 3.85 a

 Nominal thickness of the cast PMMA plate. 

 *

 Lexan is a registered trademark of General Electric Co. 

†

 Plexiglas G is a registered trademark of ATOFINA Chemicals, Inc. 
3

Two sets of glass-plastic targets were prepared—Pyrex* glass was used in one set and soda lime 

glass in the other; both were acquired from Swift Glass Company, Inc. (Elmira, NY). These 

glass-plastic targets were not bonded with any adhesives, but instead stacked together and 

wrapped tightly with heavy gauge construction tape around the sides. This practice serves well 

for the preliminary evaluation as well as for the ease of dissemble of targets in order to examine 

the damage associated with each plate from the impact. Tables 4 and 5 list the target 

configuration and the areal density of these glass-plastic laminates with Pyrex glass and soda 

lime glass, respectively. 

Table 4. Target configuration and areal density of Pyrex glass-plastic laminates. 

Target Type Laminate Configuration Areal Density 

(lb/ft2

) 

PC-Glass-PMMA-PC-1 1.5-mm PC/2.5-mm glass/6-mm 

PMMAa/1.5-mm PC 

3.53 

PC-Glass-PMMA-PC-2 1.5-mm PC/2.5-mm glass/9-mm 

PMMAa

/1.5-mm PC 

4.30 

PC-Glass-PMMA-PC-3 1.5-mm PC/2.5-mm glass/12-mm 

PMMAa/1.5-mm PC 

5.08 

a

 Nominal thickness of the cast PMMA plates. 

Table 5. Target configuration and areal density of sodalime glass-plastic laminates. 

Target Type Laminate Configuration Areal Density 

(lb/ft2

) 

PC-Glass-PMMA-PC-1 3-mm PC/3-mm glass/9-mm 

PMMAa/3-mm PC 

5.14 

PC-Glass-PMMA-PC-2 3-mm PC/3-mm glass/12-mm 

PMMAa/3-mm PC 

5.92 

a

 Nominal thickness of the cast PMMA plates. 

2.2 Ballistic Testing 

The ballistic measurements were carried out at ARL Experimental Facility Peep Sight Range 20 

at Aberdeen Proving Ground, MD, primarily using the 17-gr (1.1-g weight), .22-cal. FSP and, in 

some cases, with the 124-gr full-metal-jacket 9-mm projectile (figure 1). The target laminates 

were C-clamped at all four corners to the backside of a heavy steel test stand; the stand had a 12 

mm-diameter opening in the center. For the .22-cal. FSP, the testing was conducted using a 

0.56-m-long, 5.66-mm barrel with a 1:12 twist. For the 9-mm tests, a 9-mm Mann barrel with a 

1:9.75 twist was used. The muzzle of the gun was placed 2.5 m from the target fixture. All shots 

were conducted with the target normal to the projectile line of flight, i.e., 0° obliquity. During 

the ballistic measurements, the amount of smokeless powder that was loaded into the brass case 

was varied to control the projectile velocity. Specimens were subjected to impact over a range of 

 *

 Pyrex is a registered trademark of Corning. 
4

Figure 1. Pictures of .22-cal. FSP (left) and 124-gr, 9-mm projectile 

(right). 

striking velocities in order to achieve complete penetration and partial penetration. The ballistic 

limit, commonly referred to as V50, is a statistical value and is regarded as the velocity at which 

the projectile has a 50% chance of perforating the target at normal incidence of impact. In this 

study, at least eight test specimens of each composition were used for the ballistic measurements, 

except in the cases where only a limited number of target specimens was available for testing. 

All shots were examined for pitch, yaw, and total yaw to ensure a fair test. The V50 value was 

determined from the averaging of the lowest impact-velocity values, in which target specimens 

failed in complete penetration, and the highest velocity values associated with partial penetration. 

The spread between the impact velocity values associated with complete and partial penetration 

is within 38 m/s, following the guideline of the MIL-STD-662F specifications (4). In some 

cases, in addition to the V50 measurement, the ballistic impact energy exerted on the target was 

calculated based on the change of kinetic energy of the projectile before and after the penetration 

into the target, as shown in equation 1. The mass (M) of the projectile is assumed unchanged 

during the impact. 

Ballistic energy = 1/2 M (Vs

2

 –Vr

2

), (1) 

where Vs and Vr are the striking and residual velocities, respectively. 

2.3 Compression Measurements 

Quasistatic compression measurements of the monolithic PMMA and PC were performed by 

using the Instron model 1331 testing machine. Cylindrical shape specimens of 6-mm diameter 

with a 3-mm gauge length, yielding a diameter to depth ratio of 2:1, were selected. True straincontrolled compression testing was used at a constant-strain rate ranging from 0.001/s to 1/s; this 

mode was achieved with the use of a programmable function generator providing the command 

signal source to the auxiliary input of the Instron controller. Liberal amounts of a lubricant were 

applied to the specimen to minimize friction between the specimen ends and platens during the 

compression measurements. 
5

3. Results and Discussion 

We have examined the role of PMMA on the overall ballistic performance of the PC-PMMAPC, PMMA-PC, PMMA-Sim PU, and PC-glass-PMMA-PC systems, and will discuss the test 

results in the following sections. 

3.1 PC-PMMA-PC vs. PC-PC-PC Laminates 

The details of layer configuration and areal density of these laminates are listed in table 1. The 

PC-PMMA-PC laminates exhibit a 37% higher value of the V50 when compared with the 

PC-PC-PC laminates of equivalent overall layer configuration against the .22-cal. FSP impact 

(figure 2). These results are consistent with the earlier experimental observations; the 

PC-PMMA-PC laminates are more effective than the corresponding all-PC laminates, despite the 

fact that monolithic PC is ductile upon impact. The failure mechanisms associated with these 

two laminates are distinctly different; the all-PC laminates display localized plug failure with 

damage limited to the immediate vicinity of impact (figure 3), while radial and circumferential 

cracks form over the PMMA plate in the PC-PMMA-PC laminates (figure 4). A conoid fracture 

pattern (figure 5) is evident in the exit side of PMMA in the PC-PMMA-PC laminates, similar to 

the brittle fracture pattern observed in the typical hard ceramic systems. It is generally 

recognized that the extent in the spreading of impact energy is closely related to the ability to 

form a conoid shaped damage zone within the ceramic plate of the ceramic-metal composites 

armor. This fracture pattern is generally regarded as the major factor to the synergistic 

interaction between the brittle and ductile layers (5–7); however, it may not be the only attribute 

to the ballistic response of polymer-based hybrid composites. 

846

618

0

100

200

300

400

500

600

700

800

900

1000

PC-PMMA-PC PC-PC-PC

V50 (m/sec)

Figure 2. V50 values obtained for the PC-PMMA-PC and PC-PC-PC laminates against 

the .22-cal. FSP impact.
6

Figure 3. Typical fracture pattern of the PC-PMMAPC laminate after impact with the .22-cal. 

FSP. 

Figure 4. Typical fracture pattern of the PC-PC-PC 

laminate after impact with the .22-cal. FSP. 
7

Figure 5. Typical conoid fracture pattern observed in 

the exit side of the PC-PMMA-PC laminate 

after impact with the .22-cal. FSP. 

3.2 Effect of PMMA Plate Thickness 

We examined the ballistic performance of laminates consisting of Simula polyurethane (PU), 

instead of PC, as a back support. The V50 value of the PMMA-Sim PU laminates increases with 

increasing PMMA plate thickness (8), as shown in figure 6. In order to validate the effectiveness 

of PMMA in the PMMA-Sim PU laminates vs. in the PC-PMMA-PC and PMMA-PC laminates 

(listed in table 2), we plot the V50 values as a function of areal density, since some of these 

laminates consist of different configurations. The V50 data shown in figure 7 appear to be 

directly proportional to the areal density regardless of the laminate configuration. It is noted that 

the variation of areal density reflects primarily the difference of the plate thickness of PMMA 

used in these laminates. 

The velocity of stress wave propagation in a material is proportional to the square root value of 

Young’s modulus divided by density; therefore, the stiffer PMMA is presumably more capable 

of dissipating the shock-induced stresses than the PC and Sim PU. The V50 data shown in 

figure 7 reveal that the use of PMMA to achieve the synergistic ballistic enhancement of hybrid 

hard/ductile composites is consistent in both PMMA-Sim PU and PC-PMMA-PC (including 

PMMA-PC) laminates. These results further suggest that PMMA is effective over the selected 

range of areal densities that are of interest for structural optimization for various armor 

applications. 

3.3 Rate-Dependent Ballistic Response of PMMA 

As mentioned earlier, the monolithic PMMA exhibited equal or better impact performance 

against the .22-cal. FSP impact than PC at a thickness ~12 mm or above, as shown in figure 8 

(2, 3). We attempted to determine whether this unique impact behavior was merely targetgeometry dependent or if it was indeed characteristic of PMMA. We carried out the ballistic
8

586

672

0

100

200

300

400

500

600

700

800

6mm PMMA/3 mm PU 9mm PMMA/3 mm PU

V50 (m/sec)

Figure 6. V50 values obtained for the PMMA-Sim PU laminates against the 

.22-cal. FSP impact. 

500

600

700

800

900

1000

3 3.5 4 4.5 5 5.5 6

PC-PMMA-PC

PMMA-Sim 2003 PU

PMMA-PC

V

50 (m/sec)

Areal Density (lb/ft2)

Figure 7. Plot of V50 vs. areal density for the PC-PMMA-PC, PMMA-Sim 2003 

PU, and PMMA-PC laminates against the .22-cal. FSP impact. 
9

0

100

200

300

400

500

600

700

0 5 10 15 20

PC

PMMA

V

50 (m/sec)

Nominal Plate Thickness (mm)

Figure 8. Plot of V50 vs. nominal plate thickness of monolithic PMMA and 

PC against the .22-cal. FSP impact. 

testing of PMMA of various plate thicknesses at impact velocities in the range of 200 m/s to 

1300 m/s, well above their V50 values. PMMA exhibited a change of mode of failure from brittle 

type cracking to more localized deformation as the impact velocity increases; figures 9a and 9b 

are the representative photographs displaying the corresponding fracture patterns. The apparent 

ballistic energy values were also calculated using equation 1 and were plotted as a function of 

striking velocity in figure 10 for the 6, 9, and 12-mm thick PMMA targets. It is evident that the 

ballistic energy value increases with increasing impact velocity, which corresponds to the 

observation of brittle-to-ductile transition of PMMA with respect to the increase of impact 

velocity (see inserts in figure 10). 

3.4 Compression Measurements of Monolithic PMMA and PC 

Quasistatic compression testing was carried out to validate the rate-dependent ballistic response 

of PMMA. Measurements of the true stress vs. true strain of the monolithic PMMA and PC 

under compression were conducted at a constant strain rate ranging from 0.001/s to 1/s (9, 10). 

Results in figure 11 show that PMMA, albeit brittle upon the tensile deformation, displays 
10

(a) (b)

Figure 9. Brittle mode cracking compared to localized deformation observed in the 

6-mm thick monolithic PMMA after impact with the .22-cal. FSP at a velocity 

of (a) 173 m/s and (b) 1004 m/s, respectively. 

0

100

200

300

400

500

600

700

800

200 400 600 800 1000 1200 1400

6 mm

12 mm

18 mm

Ballistic Energy (J)

Striking Velocity (m/sec)

Figure 10. Plots of ballistic energy values as a function of striking velocity obtained for the monolithic 

PMMA of various target thicknesses against the .22-cal. FSP impact; inserts show the 

corresponding mode of impact-induced failure; solid lines are the second-order polynomial 

curve fit for the corresponding data. 
11

0

50

100

150

200

250

300

0 0.05 0.1 0.15 0.2 0.25

PMMA_1/s

PMMA_0.001/s

PC_1/s

PC_0.001/s

Stress (MPa)

Strain 

Figure 11. Plots of stress vs. strain data obtained from the 

constant-strain rate compression measurements at 

0.001/s and 1/s for the monolithic PMMA and PC. 

elastic-plastic deformation with an initial viscoelastic response followed by yielding, strain 

softening, and strain hardening in compression, similar to PC. The apparent yield stress of 

PMMA is much higher than that of PC. Furthermore, PMMA exhibits higher rate-sensitivity 

than PC; the increase of apparent yield stress with respect to the strain rate is much more 

significant in PMMA than in PC (figure 12). Table 6 lists the values of apparent compressive 

yield stress of PMMA and PC. 

3.5 PC-Glass-PMMA-PC Laminates 

Despite the fact that the state of the stress encountered at high impact velocities is very 

complicated, we hypothesized that the high strain-rate sensitivity characteristics of PMMA were 

its intrinsic material response. Furthermore, we exploited this observation to the practical use in 

the design and system optimization of transparent armor. For example, we incorporated PMMA 

as an additional intermediate ply within the typical glass-PC laminates in order to determine 

whether PMMA was effective in the PC-Glass-PMMA-PC laminate systems. As stated earlier, 

instead of using adhesive bonding, we stacked these plates together and wrapped them tightly 

with construction tape around the sides for preliminary evaluation. Figure 13 plots the V50 

values as a function of areal density obtained for the PC-Glass-PMMA-PC laminates against the 

.22-cal. FSP impact. The variation of area density reflects the difference of the plate thickness of 

PMMA used in these laminates listed in table 4; it is evident that the ballistic impact 

performance improves with incorporation of thicker PMMA plates. Figure 14 compares these 
12

60

80

100

120

140

160

180

200

10-5 0.0001 0.001 0.01 0.1 1 10

PMMA

PC

Apparent Yield Strength (MPa)

Strain Rate (s -1)

Figure 12. Comparison of the apparent compressive yield 

strength of PC and PMMA with respect to the 

strain rate. 

Table 6. Values of apparent compressive yield stress as a function of constant strain rate for the monolithic 

PMMA and PC. 

Apparent Compressive Yield Stress 

(MPa) 

Constant Strain Rate 

(s−1

) 

PMMA PC 

10−4 95.2 ± 2.1 65.8 ± 1.3 

10−3 109.7 ± 6.6 68.9 ± 1.0 

1 193.5 ± 2.8 81.7 ± 1.0 

data with all the V50 vs. areal density data available for the all-plastic laminates shown in 

figure 7; the solid lines are the linear curve-fit of these data. It is apparent that the effect of 

PMMA plate thickness on the overall ballistic performance is more significant in the glassplastic laminates than in the all-plastic laminates. Incorporating PMMA as intermediate ply 

between the glass and ductile PC presumably can provide better impedance match and 

subsequently facilitate the shock wave propagation throughout the glass-PMMA-PC systems 

than the corresponding laminates without PMMA. We also attribute the observation of the 

overall impact enhancement to the high strain-rate sensitivity characteristics of the monolithic 

PMMA, seen in figure 10, due to the fact that these glass-plastic laminates with increasing 

PMMA plate thickness encountered much higher impact velocities upon the V50 measurements. 

These results validate our intent to integrate PMMA into the design of ceramic-plastic-based 

armor for protection against emerging threats. 
13

500

600

700

800

900

1000

1100

1200

1300

3 3.5 4 4.5 5 5.5 6

V

50 (m/sec)

Areal Density (lb/ft2)

Figure 13. Plot of V50 vs. areal density data for the PC-GlassPMMA-PC laminates (listed in table 4) against the 

.22-cal. FSP impact. 

500

600

700

800

900

1000

1100

1200

1300

3 3.5 4 4.5 5 5.5 6

Glass-plastic laminates 

(Fig.13)

All-plastic laminates 

(Fig. 7)

V

50 (m/sec)

Areal Density (lb/ft2)

Figure 14. A combined plot of V50 vs. areal density data for the 

all-plastic laminates (figure 7) and PC-Glass-PMMAPC laminates (figure 13) against the .22-cal. FSP 

impact; solid lines are the linear curve fit for the 

corresponding data. 

V50 (m/s) 
14

3.6 Ballistic Measurements Against the 9-mm Projectile 

We have conducted the preliminary ballistic evaluation of selected laminate systems against the 

9-mm projectile. Table 7 summarizes the overall target configuration, areal density, and V50

values of PC-PMMA-PC, PC-PC-PC, and PC-Glass-PMMA-PC laminates (listed in table 5). 

The first two sets are all-plastic laminates with similar configuration (table 1); the PC-PMMAPC laminates nevertheless show better V50 (477 m/s) than the corresponding PC-PC-PC 

laminates (385 m/s). In addition, the PC-PMMA-PC laminates appear to be able to break the 

9-mm projectile apart during impact; figures 15 and 16 display the damaged projectile resulting 

from impact at a velocity of 480 m/s or even well below V50 at 390 m/s, respectively. The PCPC-PC laminate, on the other hand, only deforms but does not cause rupture of the 9-mm 

projectile, as shown in figure 17. 

The glass-plastic laminates consisting of 12-mm thick PMMA withstood the 9-mm projectile 

impact without complete penetration. The PC-PMMA-PC laminates with similar overall 

thickness as the PC-Glass (3-mm thick)-PMMA (9-mm thick)-PC laminates are about 9% lighter 

in terms of areal density, yet exhibit only about 6% difference in V50 (477 m/s vs. 507 m/s). 

Table 7. Areal density of PC-PMMA-PC and PC-Glass-PMMA-PC laminates and their 

corresponding V50 values against the 9-mm projectile. 

Laminate Configuration Areal Density 

(lb/ft2

) 

V50 

(m/s) 

3-mm PC/12-mm PC/3-mm PC 4.85 385 

3-mm PC/12-mm PMMAa/3-mm PC 4.68 477 

3-mm PC/3-mm Glass/9-mm PMMAa/3-mm PC 5.14 507 

3-mm PC/3-mm Glass/12-mm PMMAa/3-mm PC 5.92 b 

a

 Nominal thickness of the cast PMMA plate. b

 No complete penetration. 

Figure 15. PC-PMMA-PC laminate after impact with 

the 9-mm projectile at 480 m/s. 
15

Figure 16. PC-PMMA-PC laminate after impact with 

the 9-mm projectile at 390 m/s. 

Figure 17. PC-PC-PC laminate after impact with the 9-mm 

projectile at 399 m/s. 

Moreover, the PC-PMMA-PC laminates have significantly better residual visibility than the 

glass-plastic laminates, as shown in figure 18. These preliminary results serve as the basis for 

the further optimization studies and demonstrate that PMMA is effective and has potential as a 

replacement for glass in the design of glass-containing armor systems. 
16

Figure 18. Comparison of the extent of residual visibility seen in the PC-PMMA-PC laminate (left) and 

PC-Glass-PMMA-PC laminate (right) after the 9-mm projectile impact. 

4. Conclusions 

We have evaluated the role of PMMA on the ballistic impact performance of the selected 

all-plastic- and glass-plastic-based laminates. Results show that the ballistic limit against the 

.22-cal. FSP increased with increasing plate thickness of PMMA in these targets. Based on the 

preliminary results, the effectiveness of PMMA against the .22-cal. FSP is also evident when 

testing against the 9-mm projectile. These experimental findings suggest that PC-PMMA-PC or 

other all-plastic laminates are the systems of choice, particularly for incorporation into the design 

of vehicle transparent armor applications. We are currently undertaking this approach to 

determine the ballistic response with respect to the target thickness for the monolithic PMMA, 

PC, and Sim PUs to better understand the interaction between the projectile and each individual 

component in order to best optimize the overall target requirements against the 9-mm threats. 
17

5. References 

1. McCauley, J.; Parimal, P.; Gilde, G.; Dehmer, P. G.; Hsieh, A. J. Transparent Armor 

Systems; brochure; U.S. Army Research Laboratory: Aberdeen Proving Ground, MD, 

June 2002. 

2. Hsieh, A. J.; Song, J. W. The Role of PMMA in Ballistic Impact Response of Hybrid 

Hard/Ductile Composites. In preparation for Polymer Composites, 2003. 

3. Song, J. W.; Hsieh, A. J. Ballistic Impact Resistance of Monolithic, Hybrid and Nano 

Composites of PC and PMMA. Proceedings of the 17th American Society for Composites 

Technical Conference, Purdue University, West Lafayette, IN, October 2002. 

4. MIL-STD-662F. V50 Ballistic Test for Armor 1977. 

5. Florence, A. J. Interaction of Projectiles and Composite Armor; AMMRC-CR-69-15; Army 

Materials and Mechanics Research Center: Watertown, MA, August 1969. 

6. Hetherington, J. G. The Optimization of Two Component Composite Armours. Int. J. 

Impact Energy 1992, 12, (3), 409–414. 

7. Hetherington, J. G.; Rajagopalan, B. P. An Investigation Into the Energy Absorbed During 

Ballistic Perforation of Composite Armours. Int. J. Impact Energy 1991, 11, 33–40. 

8. Dehmer, P. G. Weapons and Materials Research Directorate Personnel Protection Work 

Area program review; U.S. Army Research Laboratory: Aberdeen Proving Ground, MD, 

2002. 

9. Moy, P.; Weerasooriya, T.; Hsieh, A. J.; Chen, W. Strain Rate Response of a Polycarbonate 

Under Uniaxial Compression. Proceedings of the SEM Annual Conference on Experimental 

Mechanics, Charlotte, NC, June 2003. 

10. Moy, P.; Weerasooriya, T.; Chen, W.; Hsieh, A. J. Dynamic Stress-Strain Response and 

Failure Behavior of PMMA. Proceedings of the ASME International Mechanical 

Engineering Conference, Washington, DC, November 2003.
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