Deformation micromechanisms

The purpose of this paper is to investigate the mechanical properties (plastic deformation, micromechanisms of deformation, fracture) of several amorphous polymers considered in [1], i.e. poly(methyl methacrylate) and its maleimide and glutarimide copolymers, bisphenol A polycarbonate, aryl-aliphatic copolyamides. Then to analyse, in each polymer series, the effect of chemical structure on mechanical properties and, finally, to relate the latter to the motions involved in the secondary transitions identified in [ 1] (in most cases, the p transition). 

The results refer to room temperature behaviour and it will be shown that the deformation micromechanism can change, depending on temperature and strain rate... 

It is important to note that within the plastic zone there is an energy dissipation originating from the deformation micromechanisms (SDZs, CSCs, or CDCs) occurring. The amount of energy thus dissipated represents almost the whole energy involved in crack propagation. 

In order to understand fracture behaviour, it is important to analyse the types of deformation micromechanisms undergone under strain chain scission craze (CSC), shear deformation zone (SDZ), chain disentanglement craze (CDC) and the temperature range over which each one occurs. Furthermore, it is worth wondering whether these micromechanisms are related to /i transition motions. 

As above mentioned, the presence of CMI units within the PMMA chain backbone makes the sample considerably more brittle. Such an effect is already reflected in the type of deformation micromechanisms more and more crazes when the CMI content increases. 

Basic mechanical behaviours, such as plastic deformation, deformation micromechanisms, and fracture, are successively presented. The characteristics of the studied polymers are gathered in Table 7. 

In the case of BPA-PC, the thin film investigation of deformation micromechanisms (Sect. 4.2) shows that CDCs occur around 60 °C. So, it is unlikely that the craze at the crack tip occurring at - 20 °C, or above, could be a CDC. The observed MW dependence of failure originates from the above described mechanism with CSCs. 

Three temperatures, T12, T223 and T233, are used to characterise the transitions between the different regimes of deformation micromechanisms, representing the transitions from low temperature CSCs to SDZs, from SDZs to... 

The goal of this investigation of the mechanical properties of amorphous polymers (plastic deformation, micromechanisms of deformation, fracture) was to analyse the influence of secondary transition motions on these properties. 

Fig. 5. Electron micrograph showing the deformation micromechanisms of A-lTo.7lo.3(32) in the vicinity of the crack tip at low temperature.

Mechanical Properties and Deformation Micromechanics of Rubber-Toughened Acrylic Polymers... 

B. Bakri and S.J. Eichhorn, Elastic coils Deformation micromechanics of coir and celery fibres. Cellulose 17,1-11, (2010). 

Details of the deformation micromechanisms of polymers can be investigated using different techniques. One of the most common approaches is to prepare specimens for TEM studies from the deformed sample taken from locations close to the fracture surface using an ultramicrotome, and this can be followed by the usual chemical and physical treatments. The thin films may also be stretched... 

Knowledge of the deformation micromechanisms of polymers is an important aspect of the fields of materials science and engineering. Indeed, precise investigations of the processes of deformation and fracture have contributed a great deal to the construction of materials with tailored properties [87-89]. 

Eichhom, S. J., Young, R. J. (2003), Deformation micromechanics ofnatural cellulose fibre networks and composites, Comp. Sci. TechnoL, 63,1225-30. 

R. J. Amodeo, N.M. Ghoniem, 1990, Dislocation dynamics. I. A proposed methodology for deformation micromechanics Dislocation dynamics. 11. Applications to the formation of persistent slip hands, planar arrays, and dislocation cells , Phys. Rev. 

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