Platelet composition

Allman, M.A., Pena, M.M., and Pang, D. 1995. Supplementation with flaxseed oil versus sunflower seed oil in healthy young men consuming a low fat diet Effects on platelet composition and function. Eur. J. Clin. Nutr. 49, 169-178. 

Pezzotti, G., (1993), Si3N4/SiC-platelet composite without sintering aids - a candidate for gas-turbine engines , J. Am. Ceram. Soc., 76 (5), 1313-1320. 

FIGURE 2. SEM micrographs showing polished cross-sections of IO-YSZ/20 moI% alumina particulate and platelet composites (a) particulate (b) platelet. Bars = 10 jim. 

Density was measured with a bulk mass/volume method using the same flexure specimens that were used in elastic modulus measurements. A total of five specimens were used for each of alumina contents. Figure 4 depicts density as a function of alumina content for both particulate and platelet composites [3, 4]. Density decreased linearly with increasing alumina content, yielding good agreement with the prediction based on the rule of mixture. The difference in density between particulate and platelet composites was negligible. 

FIGURE 4. Density as a function of alumina content for 10-YSZ/atumina particulate and platelet composites. Error bars indicate 1.0 standard deviations. The line indicates the prediction based on the rule ofmixiure [3, 4]. 

FIGURE 9. Fracture toughness as a fimction of alumina content for lO-YSZ/alumina particulate and platelet composites, determined by the SEVNB method at room temperature [2, 4]. Error bars indicate +1.0 standard. 

Slow crack growth (SCG) behavior of some chosen composites was determined at 1000°C in air using dynamic fatigue (or called constant stress-rate ) testing in accordance with ASTM test method C 1465 [16]. Three different composites including 0 mol% (10-YSZ), 30 mol% alumina particulate and 30 mol% alumina platelet composites were... 

FIGURE 12. Results of dynamic fatigue testing at 1000°C inairfor 10-YSZ, 10-YSZ/30mol% alumina particulate composite, and lO-YSZ/30 mol% alumina platelet composite. The solid lines represent the best-fit line. Slow crack growth parameter n is included. 

Elastic modulus of both particulate and platelet composites was determined from 25 to 1000°C as a function of alumina content by the impulse excitation of vibration method, ASTM C 1259 [26] using the flexure specimen configuration. One flexure specimen was used at each of alumina contents for a given composite. A total of five specimens were additionally used at each alumina content to evaluate ambient-temperature elastic modulus of the two composites. 

Microhardness of both particulate and platelet composites was evaluated at ambient temperature with a Vickers microhardness indenter with an indent load of 9.8 N using five indents for each composite in accordance with ASTM C 1327 [28]. Figure 16 shows the results of Vickers microhardness measurements for both composites. Microhardness increased linearly with increasing alumina content for the particulate composites up to 20 mol% alumina and then leveled off above 20 mol%. Microhardness of the platelet composites remained almost unchanged up to 10 mol% and then decreased appreciably at 30 mol%, resulting in a significant difference in hardness at 30 mol% between the two composites. Individual microhardness data for both composites are also summarized in Tables 1 and 2. 

FIGURE 16. Vickers microhardnessasafiinctionofaluminacontents for 10-YSZ/alumina particulate and platelet composites. Error bars indicate 1.0 standard deviations. 

FIGURE 17. Flexure strength as afunction ofnumberofthermal cycles (between 200 and 1000°C) for lO-YSZ/30 mol% alumina platelet composite [4], The numbers in parentheses indicate average strength. 

As seen from the aforementioned properties, the maximum flexure strength at 1000°C was achieved for the 30 mol% particulate composite, while the maximum fracture toughness at 1000°C was attained for the 30 mol% platelet composite. The resistance to SCG susceptibility was greater in the 30 mol% platelet composite with a higher SCG parameter of n = 33 than in the 30 mol% particulate composite with a lower SCG parameter of n = 6. 

At 1000°C, the 30 mol% particulate composites yielded the maximum strength, whereas the 30 mol% platelet composite exhibited the maximum fracture toughness. Fracture toughness was approximately 16% greater in the platelet composites than in the particulate composites. 

The susceptibility to slow crack growth was high for both 0 mol% and 30 mol% particulate composites with lower SCG parameters of n = 6-8, whereas the susceptibility to SCG was low for the 30 mol% platelet composite with its higher SCXj parameter ofn = 33. 

Thermal cycling/fatigue up to 10 cycles between 200 to 1000°C did not show any strength degradation of the 30 mol% platelet composites, indicative of negligible influence of GTE mismatch on residual stresses and/or microcracking between YSZ and alumina grains. 

V. Cannillo, G. C. Pellacani, C. Leonelh, A. R. Boccaccini, Niunerical Modelling of the Fracture Behaviour of a Glass Matrix Composite Reinforced with Alumina Platelets, Composites Part A 34, 43-51 (2003). 

Equation (2.13) has also been used to predict the modulus of flake (platelet) composites containing planar oriented reinforcement for uniform arrays of flakes, Eq. (2.14), and for random overlap, Eq. (2.15) [10, 12, 14, 19]. Equations for the parameter u are somewhat different from those used for fibers, but thqr still contain the important parameters affecting the modulus of the composite, that is, aspect ratio, volume fraction, and flake/matrix modulus ratio. Equation (2.18) has also been used to predict the modulus of platelet-reinforced plastics [17, 21]. 

Goodnight SH, Harris WS, Connor WE (1981) The effects of dietary (o-3 fatty adds on platelet composition and function in man a prospective study. Blood 58 880-885... 

Figure 11.29 Optical micrograph of the polished surface of an AI2O3/2O vol% SiC platelet composite produced by conventional sintering of coated powders, showing a fairly uniform distribution of the platelets (light phase) in a dense matrix (dark phase). The very dark areas are pores, some of which are caused by pullout of platelets during polishing.

Mendels D A, Leterriere Y and Maiison J-A E (1999) Stress transfer model for angle fibre and platelet composites, J Compos Mater 33 1525-1543. 

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