Fibre pullout

Table 18.5 Effect of sintering conditions and additives on fibre pullout in SiCf /a-sialons...

Fibre Matrix/sintering additives Hot-pressing conditions Maximum fibre pullout length (pm)... 

Short fibre composites, fibre orientation, fracture toughness, fracture mechanisms, fibre pullout, fibre debonding, critical fibre angle. 

C/SiC composites show a quasi-ductile fracture behaviour, derived from mechanisms like crack deflection and fibre pullout. Figure 14 shows exemplarily these effects within a C/C-SiC composite. The linear-elastic behaviour of C/SiC is less pronounced than for example SiC/SiC composites due to the inherent microcracks in the matrix which occur during cooling-down from processing to room temperature because of the high thermal mismatch between C-fibres and SiC-matrix. 

Miyajima T, Sakai M, Fibre pullout and fracture energy of C-fibre/C-matrix composites, Bradt RC, Hasselman DPH, Munz D, Sakai M, Ya Shevchenko V, Fracture Mechanics of Ceramics 9, Composites, R-Curve Behavior and Fatigue, Japan Fine Ceramics Center, Proc 5th Int Symp, Nagoya, Jul 15-17 1991, Plenum, 83-95, 1992. 

The mechanism of fibre reinforcement of the cementitious matrix in concrete has been extensively studied in terms of the resistance of the fibres, pullout from the matrix and as a result from the breakdown of the fibre-matrix interfacial bond. Undoubtedly, the knowledge of the individual phases as well as the interface between fibre and matrix is paramount in understanding the mechanical behaviour of FRC. There are a huge number of studies on the mechanical effect of fibres in concrete. The following sections will only... 

Fibre Pullout. The debonding mechanism in fibre-reinforced... 

Extra energy is then absorbed in fracturing the fibres and in fibre PULLOUT (q.v.) from the matrix. A fibrous fracture surface (q.v.) results, rather than the smooth continuous surface which would result from brittle fracture (q.v.) of both components were the fibre-matrix bond strength high. Most continuous fibre reinforcement is unidirectional, and... 

Markovic, 1., Walraven, J. C., van Mier, J. G. M. (2003) Experimental evaluation of fibre pullout from plain and fibre reinforced concrete , in Proc. Int. Workshop HPCFRCC 4 RILEM, Ann Arbor, 15-18 June, pp. 419-36. 

Cottrell has shovm that the work of fracture due to fibre pullout in tension for fibres of circular cross-section is given to the first approximation by... 

The apparently lov/ value of o for the 0.38 x 38 mm Duoform fibres is due to the fracture of fibres during the failure of the specimen. Since extensive fibre pullout did not occur the analysis is not applicable in this case. The results are shown,... 

However, Hibbert and Harmant found that for SFRC the energy absorbed after matrix cracking is not substantially different under slow flexure and impact conditions. This implies that the strain rate has little effect on the fibre-matrix bond properties, particularly the work of fibre pullout. This conclusion is contrary to the newer test results reported in the next paragraph of the paper. 

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