Page 337 - Engineered Interfaces in Fiber Reinforced Composites

318 Engineered interfaces in jiber reinforced composites

Table 7.5
Thermo-mechanical properties of composite constituents at 25°C".

Composite Young's modulus E Poisson ratio 11 Yield Stress uy CTE
constituents (GPa) (MPa) ( K-')

Fiber
scs-6 400 0.25 - 3.53
Matrix
Ti-24Al-llNb 1 IO 0.26 372 9.0
Coatings
Nb 98.6 0.38 248 7.13
cu 78.8 0.34 37.1 16.0

"After Arnold and Wilt (1992).
major concerns associated with CMCs for their wider applications (Tiegs et al.,
1987; Ahaim and Heuer, 1987).

7.5.2.2. Control of matrix shrinkage
It is shown in Section 6.1 that fiber pull-out following interface debonding is the
predominant failure mechanism responsible for the total toughness of most PMCs
containing glass, carbon and aramid fibers. The fracture toughness of composites
due to fiber pull-out, R,,, has been analyzed, taking into account the residual
clamping stress in the radial direction, 40, caused by the shrinkage of matrix
(Piggott, 198 1)
-40 Vfdh2A2
Rpo = (7.15)
4P(UVfA + 4d2 '

: I
-
Y
.-
C
$! LOO -
a,

0 10 20 30 LO 50
-qo in MPa

Fig. 7.24. Predicted fracture toughness of carbon and glass fiber-polymer matrix composites (CFRP and
GFRP) with varying matrix shrinkage stress, yo. After Piggott (1981).