Steel fiber-epoxy matrix composite

Fig, 4.27. Comparisons between experiments and theory of (a) maximum debond stress, oj, and (b) initial frictional pull-out stress for steel fiber-epoxy matrix composites (O) uncoated fibers ( ) release agent... 

Fig. 4.38. Comparisons of partial debond stress, (rj, between fiber pull-out and fiber push-out as a function of debond length, f, for (a) release agent coated steel fiber-epoxy matrix composites and (b) untreated SiC fiber-glass matrix composites. After Kim ct al. (1994c).

To evaluate the stability of the debond process, the instability parameter, z,nax, is compared, z ax values calculated based on Eqs. (4.104) and (4.139) respectively for fiber pull-out and fiber push-out give z ax = 6-5, 6.2 mm for coated steel wire-epoxy matrix and z ax = 0.5, 0.49 mm for the untreated SiC-fiber-glass matrix composite... 

An important feature of polymer-modified mixes is their improved bonding to old concrete or steel surfaces, which makes them particrrlarly siritable for repair work (Schulze, 1999). The addition of polyvirtyl alcohol, polyvirtyl acetate or epoxy resin to the fresh mix appears to be most effective in this respeet (Stark et ai, 1996). An improved bond may also be achieved between the fibers and eemerrt matrix in fiber-reinforced composites, resrrlting in irrrproved strength properties (Fn et al, 1996). 

Another class of inhomogeneous materials of increasing practical importance is fiber-reinforced composites. Usually the matrix is a polymer, such as epoxy. The reinforcement may be polymeric, such as Kevlar, or nonpolymeric, ie, glass, steel, or graphite. For a unidirectional composite with transverse isotropy, there are five independent elastic constants or moduli Cn, C13, C33, C44, and Cee, (28,29). Absorption measurements are particularly difficult to make on such composites. Frequently, the measured attenuation has a significant contribution as a result of scattering from the reinforcement this is sometimes referred to as geometric dispersion. 

---