Fracture of plastics

In this chapter the various approaches to the fracture of plastics are described and specific causes such as impact loading, creep and fatigue are described in detail. 

Formation in Polystyrene, paper presented at British Plastics Institute, Research Meeting on the Effect of Structure on the Fracture of Plastics— The Role of Craze in Fracture, Univ. of Liverpool, Liverpool, England (April 14, 1972). 

There can be no doubt as to the importance of plane strain conditions for the fracture of plastics especially where sharp notches and thick sections are concerned. Such conditions nearly always lead to brittle or semi-brittle fracture. Vincent has shown that the notch sensitivity in a braod range of amorphous and crystalline polymers is increased as the testing temperature is lowered and the loading rate is increased. Before fracture occurs, amorphous plastics often craze under these conditions. The complex questions of craze initiation, propagation and transformation into a crack have been treated extensively for amorphous polymers in the first three chapters of this book (see also The problem becomes more complicated when... 

A. Ivankovic, H. Jasak, A. Karac, V. Tropsa, The Prediction of Dynamic Fracture of Plastic Pipes, in Proc. 10th ACME Conference on Computational Mechanics in Engineering, Swansea (2001), 173-176. 

Melt Fracture of Plastics and Their Composites and Regrinds Surface Tearing From the preceding section it seems unlikely that potentially good or bad neat HDPE could be reliably identified in terms of runability and accompanying defects (sharkskin, roughness) of HDPE-based composite materials based only on their... 

The value of w may be higher than the true value of o by several orders of magnitude. This is the so-called Orowan problem [32], However, for a correct understanding of the aforementioned relationship, one needs to realize that the work w changes symbatically with the value of a and consequently plummets with a significant drop in o. The latter constitutes the embrittlement due to the action of a surface-active medium. The work w itself corresponds to the degree of distortion in the vicinity of the fracture surface that one needs to introduce in order to achieve a critical state. The Griffith equation can also be applied to the case of fractures of plastic bodies in which the microcrack nuclei are formed as a result of plastic strain. 

X-ray microscopy (XRM) allows non-destructive investigation of the micro-structure (fractures) of plastics, paints, adhesives, and inks. Coatings on surfaces and fibres within composite structures may be studied. Examples of X-ray micrography are the observations of inclusions in paint and ink coatings and surfaces of painted substrates. 

Fracture of plastically deforming adhesive joints 3.1. Introduction... 

ASTM D5045-91, "Plane Strain Fracture Toughness and Strain Energy Release Rate of Plastic Materials," A.nnualBook ofyiSTM Standards, ASTM Puhhcations, Philadelphia, 1993. 

Two approaches have been taken to produce metal-matrix composites (qv) incorporation of fibers into a matrix by mechanical means and in situ preparation of a two-phase fibrous or lamellar material by controlled solidification or heat treatment. The principles of strengthening for alloys prepared by the former technique are well estabUshed (24), primarily because yielding and even fracture of these materials occurs while the reinforcing phase is elastically deformed. Under these conditions both strength and modulus increase linearly with volume fraction of reinforcement. However, the deformation of in situ, ie, eutectic, eutectoid, peritectic, or peritectoid, composites usually involves some plastic deformation of the reinforcing phase, and this presents many complexities in analysis and prediction of properties. 

There are tests for physical properties such as deasity and hardness (qv) of plastics. Microscopy (qv) is important ia fracture analysis as well as ia analysis of the morphology of polymer systems for an understanding of polymer blend performance. 

Consider these in turn. Elastic and plastic deflection we have dealt with already. Tire toughness of steel is so high that fracture of a steel panel is seldom a problem. But what about the other materials The data for toughness are given in Table 27.5. 

Plastic Forming and Fracture of Metals and Alloys and of Composites 358... 

PLASTIC FORMING AND FRACTURE OF METALS AND ALLOYS AND OF COMPOSITES... 

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