Deformation and Fracture Mechanisms

The ductile behavior of semicrystaliine polymers is usually linked to neck formation, cold drawing, and strain hardening see the stress-strain curve in the lower part of Fig. 2.18. The corresponding ductile deformation processes of the spherulites are sketched in the upper part of Fig. 2.18. 

On the lamellar level, inside the spherulites, several different processes control the ductility of the polymer, which are sketched in Fig. 2.20 [6, 12]. Lamellae running parallel to the direction of strain can be deformed by interlamellar slip (Fig. 2.20(a)), tilted lamellae rotate into the deformation direction twisting of lamellae, Fig. 2.20(b)), and lamellae that are aligned perpendicular to the applied load (in the equatorial region) will be separated lamellar separation, Fig. 2.20(c)). 

At the initial stages of deformation, these processes are mainly controlled by the amorphous phase. Occasionally, microvoid formation between lamellae (in the interlamellar, amorphous regions see Fig. 2.17) supports ductile processes. 

the temperature during deformation and the loading rate strongly influence the deformation mechanisms, with two general effects [19,20]  

Therefore, with increasing temperature (decreasing load rate), the polymer network response results in a brittle-to-ductile transition and a second ductile-to-hrittle transition. The second ductile-to-hrittle transition due to chain disentanglement is similar to the effect in the amorphous polymer PC (see Fig. 1.49). 

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R. W. Hert2berg, Deformation and fracture Mechanics of Engineering Materials, John Wiley Sons, Inc., New York, 1983. 

R. W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, 4th edition, 1996. B. R. Lawn and T. R. Wilshaw, Fracture of Brittle Solids, Cambridge University Press, 1975, Chap. 3. 

R. W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, 4th edition, Wiley, 1996. 

Hertzberg, R. W., "Deformation and Fracture Mechanics of Engineering Materials", John Wiley Sons, New York, 1976. 

To fulfill the goal of final fusion application, advanced test methods and facilities for test fusion application materials that can create circumstances much closer to the real operation environment of the fusion reactor should be developed. The clarification of deformation and fracture mechanisms and the models modification at fusion reactor environment are also required. 

Zeb Zebarjad, S. M., Tahani, M., Sajjadi, S. A. Influence of filler particles on deformation and fracture mechanism of isotactic polypropylene. J. Mater. Process. Technol. 155-156 (2004) 1459-1464. 

Hertzberg, R.W. (1989) Deformation and Fracture Mechanics of Engineering Materials. Wiley, New York. Hibino, Y. and Hanafusa, H. (1985) Raman study on silica optical fibers subjected to high tensile stress. Appl. Phys. Lett., 47 812-814. 

Hertzberg RW (1996) Deformation and fracture mechanics of engineering materials, 4th edn. John Wiley and Sons, New York... 

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