calius@SU-STAR.ARPA (Emilio Calius) (12/21/85)
I am responding here because I don't know if I can mail to CSNET nodes.
There are 2 main varieties of Kevlar fiber. Kevlar 49 is the most commonly
used as reinforcement in composites, its most popular application in aerospace
presently being pressure vessels.
Specific Gravity: 1.45 --> Density = 0.053 lb/cu. in.
Tensile Strength Breaking Strain (in the fiber direction)
2740 E 6 Pascal 2.3 % (4560 denier fiber bundle)
2940 E 6 Pascal 2.31 % (380 denier fiber bundle)
for untwisted 10 in. long filaments. Note that twisting the fiber bundle results
in significant strength losses. You also should take into consideration the
fiber's level of exposure to humidity and UV radiation. The effects of loading
rate and temperature are usually less important, unless you're operating at or
over, say, 100 deg. C and/or 1000 %/sec. strain rate.
Also, as for graphite fibers, the properties of Kevlar fibers are much
lower in the transverse than in the longitudinal direction of the fibers. I
don't have information on their transverse strength, but would guess that it's
in the region of 5 % of the longitudinal strength.
WARNING: the main source for this information is the "Kevlar 49 Data Manual",
DuPont Chemical Co., Wilmington, Delaware, 1974. I don't have a more recent
reference at hand for the fibers themselves. It is entirely possible that their
performance has improved. However, a recent (1984) paper cites Kevlar fiber
bundle longitudinal strength as being 2760 E 6 Pascal.
Call you DuPont representative.
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