Fiber/coating interface

FIGURE 2. Typical tensile stress-strain behaviors measured on 2-D SiC/SiC composites possessing PyC based interphases and fabricated from untreated ortreated Nicalon (ceramic grade) fibers (a) strong fiber/coating interfaces... 

FIGURE 10. Schematic diagram showmg crack deflection when the fiber coating/interface is strong (a) or weak (b). 

S. Bertrand, R. Pailler, J. Lamon, Influence of strong fiber-coating interfaces on the mechanical behavior and lifetime of Hi-Nicalon/(PyC-SiC)n/SiC minicomposites, J. Am. Ceram. Soc. 84 787-794 (2001). 

Figure 17 Raman spectra of a glass fiber/matrix interfaces. (A) styrene monomer (B) untreated E-glass fiber coated with polystyrene, (C) E-glass fiber treated with y-methacryloxy propyl trimethoxy silane.

For the successful development of fiber-reinforced ceramics the design of the fiber/matrix interface plays a key role. The coating of the fibers should meet the following demands ... 

Engineered interface concepts with fiber coating... 

E, V and a are the Young s modulus, Poisson ratio and CTE, respectively, and the subscript i refers to the interlayer or coating. The residual stress at the fiber/matrix interface, (Tai, for the composite without an interlayer can be obtained for , =... 

Labronici, M. and Ishida, H. (1994). Toughening composites by fiber coating A review. Composite Interfaces 2, 199-234. 

SPME (Figure 2.48) can be conducted as a direct extraction in which the coated fiber is immersed in the aqueous sample in a headspace configuration for sampling air or the volatiles from the headspace above an aqueous sample in a vial (headspace SPME analyses are discussed elsewhere) or by a membrane protection approach, which protects the fiber coating, for analyses of analytes in very polluted samples [136]. The SPME process consists of two steps (Figure 2.49) (a) the sorbent, either an externally coated fiber or an internally coated tube, is exposed to the sample for a specified period of time (b) the sorbent is transferred to a device that interfaces with an ana-... 

Three underlying mechanisms are responsible for the nonlinearity.17,18 (1) Frictional dissipation occurs at the fiber/matrix interfaces, whereupon the sliding resistance of debonded interfaces, r, becomes a key parameter. Control of t is critical. This behavior is dominated by the fiber coating, as well as the fiber morphology.19,20 By varying r, the prevalent damage mechanism and the resultant non-linearity can be dramatically modified. (2) The matrix cracks... 

The thermomechanical properties of coatings at fiber-matrix interfaces are critically important. A consistent characterization approach is necessary and the most commonly adopted hypothesis is that there are two parameters (Fig. 1.8). One is associated with fracture and the other with slip.1 33,136... 

---