ANALYTICAL METHODS FOR TEXTILE COMPOSITES
of the fiber arrangement such as volume fraction. Little is known about variations of
τ
c
with volume fraction, but the available evidence suggests they are small for the ranges of
volume fraction typical of aerospace composites. Representative values of
τ
c
are 75 MPa
for the aerospace resin Shell 1895 [4.1] and 30 MPa for automotive urethanes [4.2].
(a) (b)
Figure 4-1. Arrays of ogive microcracks in (a) an AS4/1895 tape laminate (from
[4.1]) and (b) a glass/urethane triaxial braid (from [4.2]). The fiber direction is
parallel to the bands of microcracks.
0
50
100
150
200
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
Stress (MPa)
Strain
2
τ
(a) (b)
Figure 4-2. Typical stress-strain response of a polymer composite when the
deviatoric stress in plies is pure shear. (a) AS4/1895 tape laminate (from [4.1]). (b)
AS4/3501-6 plain weave (from [4.5]).
Textile composites under shear loading show stress-strain properties very like Fig.
4-2(a). Figure 4-2(b) shows a typical curve for a short shear specimen of a plain woven,
AS4/3501-6 laminate superimposed on a theoretical prediction based on a progressive
