Plastic failure or success

In addition to developing solid RP structures, work has been conducted on sandwich structures such as filament-wound plastic skins with low-density foamed core or a plastic honeycomb core to develop more efficient strength-to-weight structures. Sandwich structures using a syntactic core have been successfully tested so that failures occurred at prescribed high-hydrostatic pressures of 28 MPa (4,000 psi). 

Much of the market success or failure of a plastic product can be attributed to the initial choice of material. Even though the range of plastics has become large and the levels of their properties so varied that in any proposed application only a few of the many plastics will be suitable. 

Readers can obtain the latest and more detailed data and information from suppliers and/or software programs. The guides presented in this book only provide a means to compare the general performances of different plastics. Since new developments in plastic materials are always on the horizon it is important to keep up to date. It is important to ensure that the fabricating process to be used to produce a product provides the properties desired (Chapter 3). Much of the market success or failure of a plastic product can be attributed to the initial choices of material, process, and their cost. 

The conceptual model of the risk assessment is the framework into which the data are placed. Like the selection of endpoints, the selection of a useful conceptual model is crucial to the success or failure of the risk assessment process. In some cases a simple single species model may be appropriate. Typically, models in ecological risk assessment are comprised of many parts and attempt to deal with the variability and plasticity of natural systems. Exposure to the system may come from many different sources. The consideration of organisms at risk depends upon the migratory and breeding habits of numerous organisms, many rare and specialized. 

Test pieces are most often in the form of two-dimensional dumbbell shapes or flat strips, but there are exceptions, such as ring test pieces, sometimes used for rubbers, and three dimensional dumbbells, for certain types of plastic. Dumbbells have the basic attribute of being a way of concentrating the stresses so that failure takes place in the narrow portion and not preferentially where the test piece is gripped, although this is not always successful in practice. For textiles a dumbbell would mean that some threads at the ends were not supported, and no advantage over a flat strip has been found for many plastics films. Particular variations on these shapes have been developed for composite materials to cope with their particular properties. 

Typically, the yardstick for qualitatively measuring the internal resistance of an adhesive bond to an external load has been the determination of the strain distribution in the adhesive and adherends. This is a difficult task. Even in simple lap joints, the actual stress-strain distributions under load are extremely complex combinations of shear and tensile stresses, and are very prone to disturbance by non-uniform material characteristics, stress concentrations or locaUzed partial failures, creep and plastic yielding, etc. It is extremely difficult to accurately measure the strains in adhesive joints with such small glue Une thicknesses and such relatively inaccessible adhesive. Extensometers, strain gauges, and photoelasticity are being used with limited success." ... 

Flex life n. Informally, the number of bending-reversal cycles causing a part to fail in a particular service. Most specifically, the number of cycles to failure of a test specimen repeatedly bent in a prescribed manner. The ASTM test for plastics is D 671. The specimen, molded or cut from sheet, is subjected to load reversal at 30 Hz at a predetermined level of outer-fiber stress until it either fails or the test is discontinued. By setting up different stresses for successive specimens, one can develop a graph of stress at failure versus number of cycles to failure (usually plotted on semi-logarithmic coordinates), i.e., the flex-life curve of fatigue curve. 

Flame retardants are in a unique position among plastics additives in that they are both created by regulations and yet are threatened by other regulations. The huge 2.3 billion industry was created over the years by various industry, federal, and state statutes, which aimed to protect people from fire and smoke situations. Indeed, the Underwriters Laboratories (UL), whose standards are integral to the success or failure of flame retardants, were created by the insurance industry. Without these regulations, the plastics industry, which accounts for 85 to 90% ( 2 billion) of the global sales of flame retardants, wouldn t use these products because they are expensive and lower the physical properties of the plastics in which they are... 

The success or failure of an organisation can be influenced by the type of innovations and developments which are available in the field of recycling plastics waste. Innovative recycling methods enable the... 

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