Composite mechanical performances

Composite mechanical performances according to the reinforcement type... 

There are significant differences in composite mechanical performance as the ceramic particle quality is varied this is visible in Fig. 3. Far higher... 

Figure 4. Tensile flow curves of two Al-4.5 wt.% Cu reinforced with aluminium matrix composites, reinforced with angular and polygonal alumina particles of roughly the same size. The data show the significant improvements brought by matrix alloying (see Fig. 3) as well as the strong influence of the ceramic particle type on the composite mechanical performance. With the stronger ceramic, the material features high strength and acceptable tensile ductility despite the fact that it is more than 50% ceramic.

A usual method is the blending of natural and polypropylene (PP) fibers before formation of bands or nonwovens [3]. So preforms are obtained in form of ribbons or nonwovens ready for thermoforming. The grade of the matrix-forming PP has less effect on the tensile and flexural properties of the composites. Therefore, there are no special requirements for the blended, matrix-forming PP fibers. PP fibers of a fineness between 1.7-6.7 dtex with lengths of 40-60 mm, even PP obtained from recycling processes, may also be used. There are no differences in a composites mechanical performance when homo- or copolymers are used. 

An analysis of the composite mechanical performance indicated that the state of mixing influenced the filler-matrix interaction and the composite tensile modulus. Results showed that an increase in composite crystallinity was related to the increase in tensile modulus. It was also found that reducing the particle size of the filler has... 

A. Peled, A. Bentur and D. Yankelevsky, Effect of Atoven Fabrics Geometry on The Bonding Performance of Cementitious Composites Mechanical Performance , Advanced Cement Based Materials Journal. Vol. 7, No. 1,1998, pp. 20-27. 

Halpin (1) and Tsai (2) have presented treatises that address the effects of fiber content, orientation and properties on the composite s mechanical performance. A numerically controlled filament winding machine is capable of placing fiber in precise, three dimensional, engineered patterns. Future research addressing the molecular role of the resin s infrastructure on mechanical performance, will couple filament wound composite... 

The most exciting challenge is probably the preparation of BN nanostructures, including nanofibers and nanotubules, using the template-assisted PDCs route. Such an approach could allow us to control the morphology and size of the nanostructured BN materials to be incorporated into the BN matrix. This should significantly enhance the mechanical performance of the resulting composites compared to composites reinforced by BN microfibers. 

This research was an attempt to develop new polymers with the mechanical properties of polyarylene ethers and the dielectric properties of fluoropolymers. After initially testing the viability of the [2n+ 2n] cyclodimerization reaction for preparing high-molecular-weight polymers and testing the dielectric properties of these polymers, two polymers (one thermoplastic and one thermoset) were prepared in larger quantities to evaluate the thermal and mechanical performance of these novel compositions. The high Te thermoset was also quantitatively tested for thermal/oxidative stability. 

We have already mentioned that depending on composition, semicrystalline triblock copolymers can show some conflict between microphase separation and superstructure formation. In fact, one of the controversial aspects is the question whether block copolymers can or cannot exhibit spherulites. This is a relevant question because spherulitic structures greatly affect the ultimate mechanical properties, and the boundaries between adjacent spherulites are often weak points in mechanical performance. Kim et al. [125] studied the competition between crystallization within microphase-separated regions and reorganization into supermolecu-lar spherulites in semicrystalline PS-b-PB-b-PCL triblock copolymers. These authors found that the formation of spherulites is strongly affected by the thickness of the specimen in such a way that thin films crystallize into... 

Table 1.12 and Figures 1.10 and 1.11 confirm that polymer composites are more expensive than metals for the same mechanical performances. It is necessary to exploit their other properties to justify their use. 

In all cases, carbon fibres lead to the highest mechanical performances compared to glass and aramid fibres. Nevertheless, their impact behaviour and price restrict their consumption. Glass fibres yield the cheapest composites but performances are more limited. Table 6.10 compares the properties of the main fibre types and shows some examples of properties for a nylon matrix reinforced with short fibres of the three types. 

Table 6.26 and Figure 6.19 display some property examples for various thermoplastic composites. These are examples, some other figures exist and the classification is arbitrary but, as already noted, the mechanical performances at room temperature are especially influenced by the nature, form and size of the reinforcements. 

DSM Somos has developed a composite stereolithography material incorporating nanoparticle technology - NanoForm 15120. It exhibits high mechanical performance including a modulus superior to 5 GPa, and a HDT superior to 132°C. 

In situ synthesis of a compound or functional material on the surface of a support is usually used to prepare hybrid or composite materials. Not only are the properties of the adsorbate including mechanical performance, thermal stability, and degree of dispersion significantly enhanced by being supported or loaded on a surface by physical or chemical means, but the resulting hybrid or composite materials can also be expected to have the merits of both the compound itself and the support. 

Evans, A.G. (1989). The mechanical performance of fiber-reinforced ceramic matrix composites. Mater. Sci. Eng. A 107, 227-239. 

In summary, based on the previous studies as reviewed above, the variables which affect most the mechanical performance of composites have been identified ... 

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