Micromechanical deformation processes

Since the thickness and properties of the interphase strongly influence the characteristics of composites and the strength of the interaction determines the dominating micromechanical deformation process, many attempts have been made to characterize them quantitatively. Many various techniques are used for this purpose, and it is impossible to give a detailed account here. As a consequence a general overview of the most often used techniques is given with a more detailed account of some specific methods which have increased importance. A more detailed description of the surface characterization techniques can be found in a recent monograph by Rothon [15],... 

Incorporation of hard particles into the polymer matrix creates stress concentration, which induces local micromechanical deformation processes. Occasionally these might be advantageous for increasing plastic deformation and impact resistance, but usually they cause deterioration in the properties of the composite. Encapsulation of the filler particles by an elastomer layer changes the stress distribution around the particles and modifies the local deformation processes. Encapsulation can take place spontaneously, it can be promoted by the use of functionalized elastomers (see Sect. 6.3) or the filler can be treated in advance. 

Kim, C. M., Michler, C. H., Rosch, J., and Miilhaupt, R. 1998. Micromechanical deformation processes in toughened PP/PA/SEBS-g-MA blends prepared by reactive processing. Acta Polymerica 49 88-95. 

As the performance of the composite is profoxmdly dominated by the micromechanical deformation process, its knowledge and control are critical for the improvement of composite properties. The effect of particle characteristics and interfacial adhesion on the micromechanical deformation processes in PP-wood composites was investigated by Renner et al. [7]. They proposed a failure map as well as the practical results and considered the influence of matrix characteristics on deformation and failure in PP-natural fiber composites in other research [24]. Hietala et al. [78] studied the effect of chemical pre-treatment and moisture content of wood chips on the wood particle aspect ratio during the processing and mechanical properties of WPCs. The use of pretreated wood chips enhanced the flexural properties of the wood chip-PP composites. Moreover, the use of undried wood chips compared to dried one can improve and reduce the flexural strength and flexural modulus, respectively. On the other hand, they concluded that the use of pretreated and undried wood chips lead to the highest aspect ratio after compounding. The effect of composition and the incorporation... 

The micromechanical deformation processes that typically occur in fiber-reinforced polymers and, therefore, the mechanical properties depend on the orientation of the fibers with respect to the direction of applied load and on the degree of phase adhesion (interfacial strength) between fiber and matrix. Figure 7.2 illustrates the situation when the fibers are arranged parallel to the applied load direction. 

In spite of the imperfections of the adsorption interaction approach, can be used successfully for the characterization of matrix/filler interaction in particulate filled polymers. In these materials debonding is usually the dominating micromechanical deformation process. Stress analysis has shown that the debonding stress (/ ) depends on the reversible work of adhesion in the following way [8] ... 

Kayaisang S, Amomsakchai T, Saikrasun S (2009) Influence of liquid crystalline polymer and recycled PET as minor blending comprheological behavior, morphology, and thermal properties of thermoplastic blends. Polym Adv Technol 20 1136-1145 Kim GM, Michler GH, Reichert P, Kressler J, Mufliaupt R (1998) Micromechanical deformation processes in PA12-layered silicate nanocomposite. Polym Mater Sci Eng 79 178 Kiss G (1987) In situ composites bloids of isotropic polymers and thermotropic liquid crystalline polymers. J Polym Eng Sci 27 410... 

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