ANALYTICAL METHODS FOR TEXTILE COMPOSITES
Table 5.1 Some Models of Unidirectional Fiber Composites
Model Remarks
1. Rule of Mixtures [5.1, 5.2] Simplistic stress partitioning
2. Hill [5.4] Inaccurate for polymer composites
3. Christensen [5.5] Accurate for isotropic fibers only
4. Van Fo Fy [5.7] Accurate for isotropic fibers only
Relatively cumbersome
5. Hashin [5.3] Bounds only; but narrowly spaced for
unidirectional composites
Allows fiber anisotropy
Computer codes for the micromechanical models in [5.3-5.7] can be found as
FORTRAN subroutines in program WEAVE (Section 8).
Properties computed for AS4/epoxy and other carbon/polymer systems are
compared in Table 5.2 (computed by Dr. R. Naik using a finite element model and the
constituent data of Table 2.1).
Table 5.2 Estimated Mechanical Properties of Tows
Fiber Matrix V
f
E
11
(GPa)
E
22
(GPa)
ν
12
ν
23
G
12
(GPa)
G
23
(GPa)
AS4 Epoxy 0.65 154 11.8 0.32 0.42 5.2 4.1
AS4 Epoxy 0.70 165 12.8 0.32 0.42 6.0 4.5
AS4 Epoxy 0.75 177 13.8 0.32 0.41 7.0 4.9
AS4 Epoxy 0.80 188 15.0 0.31 0.4 8.2 5.4
IM6 Epoxy 0.65 177 10.3 0.35 0.45 5.2 3.6
IM6 Epoxy 0.70 190 11.0 0.35 0.44 5.9 3.8
IM6 Epoxy 0.75 203 11.8 0.35 0.44 6.8 4.1
IM6 Epoxy 0.80 216 12.5 0.35 0.43 8.0 4.4
AS4 PEEK 0.65 154 12.4 0.34 0.49 4.8 4.1
AS4 PEEK 0.70 165 13.4 0.33 0.48 5.5 4.6
AS4 PEEK 0.75 177 14.4 0.33 0.46 6.4 4.9
AS4 PEEK 0.80 188 15.4 0.32 0.45 7.6 5.7
AS4* ~ ~ 234 22.4 0.3 0.35 22.1 8.3
IM6* ~ ~ 269 17.2 0.34 0.39 20.7 6.2
~ Epoxy** 4.0 0.37
~ PEEK** 3.6 0.42
*Bare fiber bundle properties (strength gauge length dependent)
**Neat resin properties
