Page 311 - Engineered Interfaces in Fiber Reinforced Composites

292 Engineered interfaces in fiber reinforced composites

1.6
a
5 1.4-
CJ) 0
2 1.2-
0.. 0.
g m 1: 0 a
0.8 - 0
x -
'- 0.6
.E - 0.4 -
a
E 0.2-
I . I
,4

1.41

.- 5 0.4 t

0.8
N
3 0.6
E
z

" 0 0.1 0.2 0.3 0.4
(b) Coating thickness, P m

Fig. 7.8. (a) Normalized impact fracture toughness and (b) interlaminar shear strength (ILSS) of carbon
fiber-epoxy matrix composites as a function of glycidyl acrylate/methyl acrylate (GA/MA) interlayer
thickness. After Rhee and Bell (1991).

the longitudinal and transverse directions, in particular for those coatings
providing a low bond strength with the fibers. Systematic reductions in flexural
strength and ILSS with increasing coating thickness, e.g. silicon rubber coating
(Hancox and Wells, 1977) and polyvinyl acetate (PVA) coating (Kim and Mai,
1991b), have been reported.
(4) There are contradicting views with regard to the reactivity and miscibility of the
coating material with the resin matrix during curing. Sung et al. (1977) suggested
that the coating should form and remain in a discrete layer at the interface
without reaction with the composite constituents. However, a certain degree of