AMPTIAC Quarterly, Vol. 9, No. 2, Summer/Fall 2005 - Advanced ...

Table 1. Typical Fiber Properties. a
Glass
Aramid
HMWPE
PBO
PIPD
Fiber Density (g/cm 3 ) Elastic Modulus (GPa) Tensile Strength (MPa) Strain to Failure (%)
S-glass[10] 2.48 90 4400 5.7
Technora[10] 1.39 70 3000 4.4
Twaron[10] 1.45 121 3100 2.0
Kevlar 29[17] 1.44 70 2965 4.2
Kevlar 129[17] 1.44 96 3390 3.5
Kevlar 49[17] 1.44 113 2965 2.6
Kelvar KM2[18] 1.44 70 3300 4.0
Spectra 900[17] 0.97 73 2400 2.8
Spectra 1000[17] 0.97 103 2830 2.8
Spectra 2000[19] 0.97 124 3340 3.0
Dyneema[20] 0.97 87 2600 3.5
Zylon AS[20] 1.54 180 5800 3.5
Zylon HM[20] 1.56 270 5800 2.5
M5 (2001 sample)[21] 1.70 271 3960 1.4
M5 (goal)[21] - 450 9500 2.5
aThe data presented are typical values and thus will vary dependent upon fiber denier.
3000
2500
0.30 cal. Fragment Simulating Projectile
3000
2500
0.30 cal. Fragment Simulating Projectile
V 50 (ft/s)
2000
1500
1000
Spectra 1000,
650 denier-plain weave
Kevlar 29,
1500 denier-basket weave
500
0 1 2 3 4 5 6 7 8
Areal Density (lb/ft 2 )
V 50 (ft/s)
2000
1500
1000
500
Spectra 1000,
650 denier-plain weave
Kevlar 29,
1500 denier-basket weave
0 0.2 0.4 0.6 0.8 1 1.2
Thickness (in.)
(a) V 50 versus Areal Density
(b) V 50 versus Thickness
Figure 9. V 50 Comparison of Fabrics[18].
Polypyridobisimidazole
A new high performance fiber – polypyridobisimidazole
(PIPD), denoted M5 ®†† – has been developed at Akzo Nobel
and shows promising results. Similar to PBO, it is a rigid-rod
structure as shown in Figure 8. Due to strong intermolecular
hydrogen bonding, however, its compressive strength is significantly
improved over that of PBO fibers. Its decomposition
temperature is about 985°F, which is close to that of PBO
fibers.[12] The fabrication technologies for M5 fibers are still
in developmental phases, as some properties of the fibers fall
short of their theoretical potential.
Comparison of High Performance Fibers
As discussed in the section on energy absorption mechanisms,
the major properties used to assess probable ballistic performance
are the tensile strength, elastic modulus, and strain to
failure. Table 1 provides a general comparison of these properties,
along with density, for the various high performance
fiber materials. Note the difference in tensile strength
between Kevlar 29 used for the old PASGT vests and Kelvar
KM2 used for the new Interceptor vests. The HMWPE and
aramid fibers are used as fabrics for flexible military body
armors, whereas S-2 Glass is used in rigid composite armor
applications. PBO fibers have not been used for military
applications, and M5 is still in developmental stages. Both
HMWPE and aramid fibers are also used in fiber-reinforced
PMCs for rigid armor applications. Figure 9a indicates that
Spectra 1000 fabrics provide a higher V 50
PBL at a lighter
weight than Kevlar 29. Figure 9b shows that Spectra 1000
provides a higher level of protection at the same thickness as
Kevlar 29 up until approximately 0.7 inches, where the level
of protection provided by the two fibers is approximately
equal. At thicknesses greater than 0.7 inches Kevlar 29 outperforms
Spectra 1000 in terms of ballistic performance.
RESINS
Resins for fiber-reinforced polymer matrix composite armors
can be either thermoplastics or thermosets. In general, thermoplastics
offer greater impact resistance and processibility,
but lack the thermal and chemical resistance of thermosets.
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The AMPTIAC Quarterly, Volume 9, Number 2