Page 116 - Engineered Interfaces in Fiber Reinforced Composites

Chapter 4. Micromechanics of stress transfer 99

t

U
2L
Fig. 4.3. Normalized average fiber axial stress, uf, as a function of fiber length, according to Eq. (4.4).

fiber length should at least not be shorter than the critical transfer length, (2L),, the
idea of which was proposed by Kelly and Tyson (1965). The implication of the
critical transfer length in evaluating the interface properties has been discussed in
Section 3.2.3.
A modified shear-lag model has been proposed by Rosen (1964, 1965) based on a
multiple fiber composite. Fig. 4.4 shows the composite model Rosen considered
wherein a fiber is embedded in a matrix which in turn is surrounded by an average
composite material. The FAS and IFSS are given in the same form as those of Eqs.
(4.1) and (4.2) given earlier by Cox (1952):

Fiber
Matri
Composi

Fig. 4.4. hi-symmetric single fiber composite model employed by Rosen (1964).