Tensile fracture

Ej (nominal) strain after fracture tensile ductility (dimensionless)... 

Fig. 11. Fractured tensile specimen from 2D-C/SiC with marked fiber pull-out...

Cracks larger than 2aCT will grow spontaneously under the applied stress, because the energy will decrease in that case, whereas cracks smaller than 2acr are stable under the applied stress. Accordingly, the fracture tensile stress, i.e. the stress needed to increase the length of a crack, is... 

From Eq. (13.146) it becomes clear that Ktc is easy to determine from the fracture tensile stress and the crack length, so that also Gic can be calculated easily. The equations above are valid for thin, wide sheets, i.e. if the width W is very large with respect of the crack length (in mathematical terms as long as tan(a/W)a/W, see, e.g. McCrum et al., General References, 1997). If this condition is not obeyed, Kk becomes dependent on the width of the sheet, so that, in contrast with GiC, the stress intensity factor KIC is not a material property. 

Fig. 30a-c. Optical micrographs of PS film squares during a "fragility test illustrating a craze initiation, b local fibril breakdown and c catastrophic fracture. Tensile stress lies along the horizontal direction (From Ref. courtesy Macromolecules (ACS))... 

Figure 5. Optical micrographs of fractured tensile specimens showing shear-deformation bands viewed between crossed, polarizing filters to enhance contrast between the birefringent bands and the undeformed matrix (a) bands typical of those observed in 2L, 3LA, 3LA/, 3LE, and 4L materials (b) bands typical of those observed in 3LB and 3LD materials and (c) bands observed in 3LC materials.

Fig. 8.14 Macrographs of fractured tensile samples having tensile axes perpendicular to the local long u y °...

The retention of the properties correlated well with the unperturbed morphology of the compositions before and after recycling. This was confirmed by transmission electron microscopy on the fractured tensile samples. Structure-property relationships were attempted to be formulated using several characterization techniques. 

Fig. 5. The fast-fracture tensile strengths (inserted table) and Weibull probability plots of AI,0 /Y Als0i2 eutectic libers.

The quantitative program goals are 1) mean RT tensile strength of 900 MPa and Weibull modulus of 20, 2) mean 1370°C fast fracture tensile strength of 500 MPa, and 3) mean 1230 C tensile stress rupture life of 100 hours at 350 MPa,... 

It was interesting to note that the specimens which survived the 100-hour exposure time fractured at stress levels higher than the fast-fractured tensile strength measured at 1400 C. It is believed that the improved tensile strength is due to some strengthening mechanism which occurs as a result of the tensile stress and temperature exposure of the specimen in air for 100 hours (surface flaw healing, etc.). 

ROOM TEMPERATURE POST-FRACTURE TENSILE (PET) STUDY OF TWO FIBER-REINFORCED CERAMIC MATRIX COMPOSITES WITH A STRONG FIBER/MATRIX INTERFACE... 

Brittle fracture Tensile failure brittle failure Elastomers, high modulus fibers (e.g. aramids) 29... 

Tensile modulus,GPa Strain to fracture Tensile strength GPA... 

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