Fiber reinforced composites stress parameters

More recently, DiCarlo (1997) has compared ceramic composites to the best superalloy using the strength-to-density ratio versus the Larson-Miller parameter, q. In this analysis (Figure 3-25), the Nextel 720 fiber-reinforced composite is inferior to the metal in short-term fracture but comparable to the superalloy in long-term rupture. On this basis, the Hi-Nicalon fiber is superior to the superalloy except at short times and high stress levels, when fiber failure is dominated by slow... 

The mechanical properties of the natural fiber-reinforced composites are dependent on some parameters such as volume fraction of the fibers, fiber aspect ratio, fiber-matrix adhesion, stress transfer at the interface, and fiber orientation [32]. Several studies on natural fiber-reinforced composites involve mechanical properties characterization as... 

The various parameters like fiber aspect ratio, volume fraction of the libers, its orientation, stress transfer at the interface and liber matrix adhesion influence the properties of natural fiber reinforced composites. The mechanical properties of the composites greatly depend on the influence of various treatments of libers, liber content, and the use of cross-linking agents (Garcia et al. 1995 Vollenberg and Heiken 1989). 

To gain a better understanding of the creep behavior of fiber-reinforced ceramics, a simple 1-D analytical approach will be used to examine the effects of constituent behavior on composite creep deformation and changes in internal stress. Since the derivation of the model provides valuable insight into the parameters that influence composite creep behavior, the derivation of the 1-D concentric cylinder model will be outlined first. 

The strength of the fiber-matrix interface is one of the key parameters responsible for the stress-strain behavior and damage tolerance of ceramic composites. Two different types of tests are available to measure the fiber-matrix interfacial properties in fiber-reinforced ceramic composites. The first is based on an indentation technique to either push the individual fiber into or through the matrix. The second test method relies on pulling a single fiber out of a matrix. These methods have been compared59 to one another for a glass matrix material, and yield similar results. 

The matrix allows the necessary positioning of the fibers, transfers the load to the fibers and distributes the stress among them, and is also responsible for protecting the reinforcement from the environment. However, the matrix is often the weakest component of a composite. One important parameter for the material properties is the fiber-matrix interface (or interphase), which guarantees the stress transfer from fiber to fiber via the matrix. The interface/interphase is a finite thin layer with its own (very often unknown) physical and chemical properties that depend on the fiber-matrix combination. Because of the low viscosity of the thermoset precursors, they wet the reinforcement better than a thermoplastic polymer. 

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