Mechanical properties deformation

The consequences of secondary transition motions on the mechanical properties (deformation, yield and fracture) of amorphous polymers are addressed in a second paper in this volume [1]. 

Keywords Polyelectrolytes Multilayers Mechanical properties Deformation Shells Capsules... 

Singleton ACN, Baillie CA, Beaumont PWR, Peijs T (2003) On the mechanical properties, deformation and fracture of a natural fibre/iecycled polymer composite. Compos B 34 519-526... 

Mechanical Properties, Deformation Behaviour, and Rock Stress... 

The molar sound velocity can be predicted with group additivity techniques. It, in turn, may be used to predict the mechanical properties due to high-frequency deformations. 

The kinetic nature of the glass transition should be clear from the last chapter, where we first identified this transition by a change in the mechanical properties of a sample in very rapid deformations. In that chapter we concluded that molecular motion could simply not keep up with these high-frequency deformations. The complementarity between time and temperature enters the picture in this way. At lower temperatures the motion of molecules becomes more sluggish and equivalent effects on mechanical properties are produced by cooling as by frequency variations. We shall return to an examination of this time-temperature equivalency in Sec. 4.10. First, however, it will be profitable to consider the possibility of a thermodynamic description of the transition which occurs at Tg. 

An important aspect of the mechanical properties of fibers concerns their response to time dependent deformations. Fibers are frequently subjected to conditions of loading and unloading at various frequencies and strains, and it is important to know their response to these dynamic conditions. In this connection the fatigue properties of textile fibers are of particular importance, and have been studied extensively in cycHc tension (23). The results have been interpreted in terms of molecular processes. The mechanical and other properties of fibers have been reviewed extensively (20,24—27). 

Table 13 is a representative Hst of nickel and cobalt-base eutectics for which mechanical properties data are available. In most eutectics the matrix phase is ductile and the reinforcement is britde or semibritde, but this is not invariably so. The strongest of the aHoys Hsted in Table 13 exhibit ultimate tensile strengths of 1300—1550 MPa. Appreciable ductiHty can be attained in many fibrous eutectics even when the fibers themselves are quite britde. However, some lamellar eutectics, notably y/y —5, reveal Htde plastic deformation prior to fracture. 

Mechanical properties of mbber-modifted epoxy resins depend on the extent of mbber-phase separation and on the morphological features of the mbber phase. Dissolved mbber causes plastic deformation and necking at low strains, but does not result in impact toughening. The presence of mbber particles is a necessary but not sufficient condition for achieving impact resistance. Optimum properties are obtained with materials comprising both dissolved and phase-separated mbber (305). 

Plastic working of a metal such as steel is the permanent deformation accompHshed by applying mechanical forces to a metal surface. The primary objective is usually the production of a specific shape or si2e (mechanical shaping), although increasingly it also involves the improvement of certain physical and mechanical properties of the metal (mechanical treatment). These two objectives can be readily attained simultaneously. 

Film Adhesion. The adhesion of an inorganic thin film to a surface depends on the deformation and fracture modes associated with the failure (4). The strength of the adhesion depends on the mechanical properties of the substrate surface, fracture toughness of the interfacial material, and the appHed stress. Adhesion failure can occur owiag to mechanical stressing, corrosion, or diffusion of interfacial species away from the interface. The failure can be exacerbated by residual stresses in the film, a low fracture toughness of the interfacial material, or the chemical and thermal environment or species in the substrate, such as gases, that can diffuse to the interface. 

Resilient Diners. Resilient liners reduce the impact of the hard denture bases on soft oral tissues. They are designed to absorb some of the energy produced by masticatory forces that would otherwise be transmitted through the denture to the soft basal tissue. The liners should adhere to but not impair the denture base. Other critical properties include total recovery from deformation, retention of mechanical properties, good wettability, minimal absorption of... 

A. H. Cottrell, The Mechanical Properties of Matter, Wiley, 1964, Chap. 9. R. W. K. Honeycombe, The Plastic Deformation of Metals, Arnold, 1968,... 

In summary, then, design with polymers requires special attention to time-dependent effects, large elastic deformation and the effects of temperature, even close to room temperature. Room temperature data for the generic polymers are presented in Table 21.5. As emphasised already, they are approximate, suitable only for the first step of the design project. For the next step you should consult books (see Further reading), and when the choice has narrowed to one or a few candidates, data for them should be sought from manufacturers data sheets, or from your own tests. Many polymers contain additives - plasticisers, fillers, colourants - which change the mechanical properties. Manufacturers will identify the polymers they sell, but will rarely disclose their... 

Perhaps the most important innovation of all is in the thermomechanical control processes, involving closely controlled simultaneous application of heat and deformation, to improve the mechanical properties, especially of ultra-microalloyed compositions. Processes such as controlled rolling are now standard procedures in steel mills. 

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