Fiber pullout, failure mode

Depending on x, Gf, and g, two failure modes are possible for aligned short brittle fiber composites fiber pullout and fiber fracture. Let us consider a composite in which > e. If / < 4, the average stress in the fiber will be given by Eq. (15.47), so the strength in the composite can be written... 

The main advantage of CMCs over monolithic ceramics is their superior toughness, tolerance to the presence of cracks and defects, and non-catastrophic mode of failure. It is widely accepted that in order to avoid brittle fiacture behavior in CMCs and improve the damage toloance, a weak fiber/matrix interface is needed, which serves to deflect matrix cracks and to allow subsequent fiber pullout . Historically, following the development of SiC fibers, fiber coatings such as C or BN have been employed to promote the desired composite behavior. However, the non-oxide fiber/non-oxide matrix composites generally show poor oxidation resistance , particularly at intermediate... 

The incorporation of short fibers into polymers greatly affects their fracture behavior. Several modes of failure would occur in the short fiber reinforced polymer composites including fiber breakage, crack deflection, crack bridging, fiber pullout and matrix deforraa-... 

SEM analysis led to the identification of different microstructural features between the two composites. The alumina matrix composite exhibited single fiber pullout after complete fiber pullout, while fiber bundle pullout dominated in the muUite/alumina composite. Comparing Figures 4 and 5 in this work, one can see a larger displacement to total failure for the alumina matrix composite than for the muUite/alumina, suggesting that fiber bundle pullout represents a more severe failure mode. Figure 9 and 10 show the fiber pullout mode for the alumina matrix and for the muUite/alumina matrix composite, respectively. 

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