Frameworks polymers plasticity

Let us consider, which processes result to necessary for yielding realization fluctuation free volume increasing. Theoretically (within the frameworks of polymers plasticity fractal concept [35] and experimentally (by positrons annihilation method [22]) it has been shown, that the yielding pro-... 

The value % can be determined within the frameworks of polymers plasticity fractal concept [35] according to the Eq. (4.9). The dependence of on shows increasing at growth [102]. At small values all crystallites are subjected to disordering owing to that yield tooth in BPE curves stress-strain is absent and these curves are acquired the form, which is typical for rubbers. Hence, stress decay beyond yield stress intensification is due tox growth [103],... 

A good elastomer should not undergo plastic flow in either the stretched or relaxed state, and when stretched should have a memory of its relaxed state. These conditions are best achieved with natural rubber (ds-poIy-2-methyl-1,3-butadiene, ds-polyisoprene Section 13-4) by curing (vulcanizing) with sulfur. Natural rubber is tacky and undergoes plastic flow rather readily, but when it is heated with 1-8% by weight of elemental sulfur in the presence of an accelerator, sulfur cross-links are introduced between the chains. These cross-links reduce plastic flow and provide a reference framework for the stretched polymer to return to when it is allowed to relax. Too much sulfur completely destroys the elastic properties and produces hard rubber of the kind used in cases for storage batteries. 

Allen [240], Costanzo et al. [241], and Krajcinovic [242-244] that thermodynamics of appropriate internal state variables for damage in composites under mechanical loads were addressed. Similar to the metal plasticity theoreticians, these researchers employed Coleman and Gurtin s [11] thermodynamic framework to determine the kinetic equations. However, unlike the metal internal state variable community that could quantify the evolution equations for dislocations and damage, these polymer-based composites theoreticians did not propose evolutionary rate equations, but just damage state equations. 

The formulation above is assumed to hold for temperatures up to the glass transition Tg. For T > Tg, most studies found in the literature focus on the description of the molten state [14] due to its practical importance, while little attention is paid to the response of glassy polymers in the rubbery state, near Tg. For strain rates larger than 1 s 1, the mechanical response of the molten material is non-Newtonian for most polymers and described by r = qym, where q and m are material parameters. We assume that this non-Newtonian response prevails as soon as Tg is exceeded. Hence, within the same framework as used below Tg, the equivalent plastic strain rate (Eq. 3) is replaced by... 

Applications of linear elastic fracture mechanics (primarily) to the brittle fracture of solid polymers is discussed by Professor Williams. For those not versed in the theory of fracture mechanics, this paper should serve as an excellent introduction to the subject. The basic theory is developed and several variants are then introduced to deal with weak time dependence in solid polymers. Previously unpublished calculations on failure times and craze growth are presented. Within the framework of brittle fracture mechanics and testing this paper provides for a systematic approach to the faOure of engineering plastics. 

Recently, a new kind of plastic crystal composite electrolytes with the polymer matrix as a mechanically reinforcing framework was designed to prepare flexible LJBs with high mechanical strength. For example, a UV-curable semiinterpenetrating polymer network matrix was used to form the plastic crystal composite electrolyte, which indicated a remarkable improvement in flexibility (Ha et al., 2012). 

Shojaei, A. and Li, G. (2013) Viscoplastidty analysis of semicrystalline polymers a multiscale approach within micromechanics framework. International Journal of Plasticity, 42, 31 9. 

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