Fiber rupture

However, in composites, mechanical properties of composites. The fiber strength in a PCM [Pg.20]

The parameter is a function of fiber rupture time (<) and temperature 7). Here D = log (Go) = 22 for the SiC and AI2O3 fibers in the high-temperature range where creep cavitation... 

Here Qr is the effective stress-dependent activation energy for fiber rupture T (kelvin) is the absolute temperature for the rupture test and tr (hours) is the fiber mpture time. Complete q-maps covering a wide range of temperatures and stresses are shown in Fig. 4a for two types of oxide fibers Nextel 610 and Nextel 720, and for three types of SiC fibers Hi-Nicalon, Sylramic, Sylramic-iBN. Here the curves represent best-fit averages of the fiber rupture times as measured for a 25 mm gauge length. 

Matrix Rupture, Fiber-Rupture Rupture life in air at upper use... 

The aspect of the flow curves in Fig. 9.6 indicates the predominant condition of the test. For instance. Fig. 9.6a shows uniform serrations (stick-shp) associated with a continuous, step-by-step process of fiber slipping away off the polymeric block. This exclusive pullout mechanism occurred only in the first part of the curve depicted in Fig. 9.5c. In this case, the fiber was intact after the test and, in some cases, covered with a layer of polyester. By contrast. Fig. 9.6d shows a smooth curve up to fracture. In this case, no pullout process occurred, and the fiber had undergone tensile rupture in association with the last horizontal part of the curve. The intermediate condition of both pullout and fiber rupture are shown in Fig. 9.6b, c. 

Although long-fiber composites typically fail at low tensile strains, they are generally not considered to be brittle, i.e., in the realm of glass or ceramics. The fibers do have strain to failure, and the failures can be predicted. A bundle of fibers bound together hy a matrix does not usually fail when the first fiber ruptures. Instead, the final failure is preceded by a period of progressive damage. 

M. Maalej, V.C. Li and T. Hashida, Effect of fiber rupture on tensile properties of short fiber composites , ASCE J. Engineering Mechanics. 121, 1995, 903 913. 

---