Deformation of glassy polymer

The constitutive model used to describe large plastic deformations of glassy polymers involves a separate formulation for temperatures above and below the glass transition Tg, since the underlying deformation mechanisms are different. In either regime, the formulation is based on the decomposition of the rate of deformation into an elastic part and a plastic part Z)P so that 0 = 0° + D. By assuming an isotropic yield stress, the isochoric plastic strain rate is given by the flow rule... 

Arruda, E. M., Boyce, M. C., and Jayachandran, R. (1995) Effects of strain rate, temperature and thermo mechanical coupling on the finite strain deformation of glassy polymers, Mech. Mater., 19, 193-212. 

Mulliken, A. D. and Boyce, M. C. (2006) Mechanics of the rate-dependent elastic plastic deformation of glassy polymers from low to high strain rates, Int. J. Solids Structures, 43, 1331-1356. 

Boyce, M.C., Parks, D.M., and Argon, A.S. (1988) Large inelastic deformation of glassy polymers, Part I Rate-dependent constitutive model. Mechanics of Materials, 7, 15-33. 

Argon, A.S. (1963) A theory for the low-temperature plastic deformation of glassy polymers. Philosophical Magazine, 28, 839-865. 

After withdrawal of high stresses below Tg, the large strains do not disappear. However, if the polsrmer is then heated above Tg, the specimen recovers its original size completely. Thus the deformation of glassy polymers is recoverable. 

D. M. Parks, A. S. Argon, and B. Bagepalli, Large Elastic-Plastic Deformation of Glassy Polymers , Program in Polymer Science and Technology, Technical Report,... 

A. Hasan and M. C. Boyce, Energy Storage During Inelastic Deformation of Glassy Polymers , Polymer 34, 5085-5092 (1993). 

Descriptions of inelastic deformation of glassy polymers are based on the classical treatments of Frenkel [269] and Eyring with coworkers [109,270] who have considered an elementary plastic flow event as a transition of a particle from one quasi-equilibrium state to another by means of overcoming a potential barrier under the influence of thermal fluctuations it is also assumed that its height is lowered by stress. Generally, the polymer deformation rate can be described by the expression... 

Table 8 shows that for polymers strongly differing in chemical structure the barrier qi coincides with or is close to the value of ficoh/3. Inelastic deformation of glassy polymers somewhat reduces the IMI energy (see Sect. 4.4) decreasing barriers qi at = 20% reflects this process. 

Thus, the main contribution to the kinetics of deformation of glassy polymers is provided by molecular motions prevailing in the given temperature region or corresponding to the nearest relaxation transition, due to stress activation of the part of the relaxation time spectrum that is located just above the temperature of the deformation experiment. 

Argon, A. S., Bessonov, M. I. (1977). Plastic Deformation in Polyimides, with New Implications on the Theory of Plastic Deformation of Glassy Polymers. Phil. Mag. 35(4), 917-933. 

Figure 12.28 Plastic strain increment by formation of a pair of kinks in a polymer molecule. (Redrawn from Argon, A.S. (1973) A theory for the low-temperature plastic deformation of glassy polymers. Phil. Mag., 28, 839. Copyright (1973) Taylor and Francis.)...

Moreover, profuse microvoids were found in the LIB fibers by using a focus ion beam (FIB) method (The images can be found in Ref. [233]). Other than the crazes usually observed in the plastic deformation of glassy polymers, the microvoids in the LIB fibers were empty and aligned in the fiber direction. Such microvoids were similar to those observed during deforming semicrystalline... 

Crazing is a massive phenomenon involved in plastic deformation of glassy polymers. 

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