Particulate reinforced composite

Creep Resistsince. Studies on creep resistance of particulate reinforced composites seem to indicate that such composites are less creep resistant than are monolithic matrices. Silicon nitride reinforced with 40 vol % TiN has been found to have a higher creep rate and a reduced creep strength compared to that of unreinforced silicon nitride. Further reduction in properties have been observed with an increase in the volume fraction of particles and a decrease in the particle size (20). Similar results have been found for SiC particulate reinforced silicon nitride (64). Poor creep behavior has been attributed to the presence of glassy phases in the composite, and removal of these from the microstmcture may improve the high temperature mechanical properties (64). 

In contrast to the particulate-reinforced composites, all other reinforcement morphologies appear to provide enhanced creep resistance. The creep... 

For particulate-reinforced composite materials, Paul derived upper and lower bounds on the composite modulus [3-4]. His approximate mechanics of materials solution agrees fairly well with experimental data for tungsten carbide particles in cobalt. 

Creep resistance -of particulate reinforced composites [COMPOSITE MATERIALS - CERAMIC MATRIX] (Vol7)... 

In the presentation of the elevated temperature mechanical behavior of ceramic matrix composites, some degree of separation has also been made between fiber-reinforced and whisker- or particulate-reinforced composites. This has been necessary because of the way the field has evolved. The continuous fiber-reinforced composites area in many ways has evolved as a field in its own right, driven by developments in fiber processing technology. 

Improvement in the creep resistance of whisker-reinforced composites is modest compared to that obtained in particulate-reinforced composites. Creep... 

Figure 7.18 shows schematic crack paths through (a) water ice and (b) ice cream. The weakest part of the water ice microstructure is the ice-matrix interface, so the crack follows a path along the edges of the ice crystals as far as possible. In the ice cream, the air bubbles are the weakest links so the crack passes through them. The ice crystals are the most fracture-resistant components so in both cases the crack passes around them. Ice cream is effectively a particulate-reinforced composite material, i. e. a material in which tough particles are embedded in a relatively soft continuous phase in order to increase the overall fracture resistance. Since the microstructure is heterogeneous, it is not possible to predict exactly where the crack will form or precisely what path it... 

There have been a number of attempts to produce more appropriate predictions of the Young s modulus of particulate reinforced composites, without having such widely-separated bounds on the predictions. They have also been reviewed recently by Young et a/. A number of years ago, Halpin and Tsai developed an approach based upon the self-consistent micromechanics method of Hill that enabled prediction the elastic behaviour of a composite for a variety of both fibre and particulate geome-... 

The volume fraction of the TCP phase is denoted as /tcp- For the particulate reinforced composite, its volume fraction can be calculated using... 

For particulate reinforced composite, differentiating Equations [5.14] and [5.16] with respect to time gives... 

Corrosion Proporlios. Marine corrosion of silicon carbide/aluminum composites is much less severe than that observed on graphite/aluminum MMCs. Discontinuous silicon carbide/aluminum MMCs, however, are susceptible to localized corrosion. Mild-to-moderate pitting has been reported on SiC whisker- and particulate-reinforced composites containiirg 6061 and 5000 series aluminum matrices exposed for a maximum of 42 months in splash/spray and marine atmospheric environments. The d ree of corrosion present on the composites is slightly accelerated compared to that on unreinforced alutrtittum alloys. 

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