Strain Engineering Plastics

In particular, it should be noted that the past traditional equations that have been developed for other materials, principally steel, use the relationship that stress equals the modulus times strain, where the modulus is constant. Except for thermoset-reinforced plastics and certain engineering plastics, most plastics do not generally have a constant modulus of elasticity. Different approaches have been used for this non-constant situation, some are quiet accurate. The drawback is that most of these methods are quite complex, involving numerical techniques that are not attractive to the average designers. 

When an engineering plastic is used with the structural foam process, the material produced exhibits behavior that is easily predictable over a large range of temperatures. Its stress-strain curve shows a significantly linearly elastic region like other Hookean materials, up to its proportional limit. However, since thermoplastics are viscoelastic in nature, their properties are dependent on time, temperature, and the strain rate. The ratio of stress and strain is linear at low strain levels of 1 to 2%, and standard elastic design... 

Because of the highly strained ring system, polymerization readily occurs via ring opening, yielding a linear polyester that exhibits properties suitable for use as a textile fiber or as an engineering plastic. 

Figure 3.31 Stress vs. strain for Mitsubishi Engineering-Plastics lupital F20-02—medium viscosity, general purpose acetal copolymer resin.

Figure 3.37 Flexural stress vs. strain at various temperatures for Mitsubishi Engineering-Plastics lupital acetal copolymer resin [4].

Figure 6.65 Stress vs. strain at various temperatures for DSM Engineering Plastics Stanyl TE200F6—30% glass fiber reinforced, heat stabilized Nylon 46 resin.

Fig. 2. A stress—strain curve in tension ts pical for engineering plastics.

The area under stress-strain curve is proportional to the energy required to break and is a measure of the toughness of the material. Typical engineering plastics exhibit curves characteristic of hard and strong or hard and tough materials. 

DMA provides material scientists and engineers with the information necessary to predict the performance of a material over a wide range of conditions. Test variables include temperature, time, stress, strain, and deformation frequency. Because of the rapid growth in the use of engineering plastics and the need to monitor their performance and consistency, dynamic thermal analysis has become the fastest growing thermal analysis technique. 

When an engineering plastic resin is used with the structural foam process, the material produced exhibits behavior that is predictable over a large range of temperatures. Its stress-strain curve shows a significantly linearly elastic region like other Hookean materials, up to its proportional limit. 

In these expressions, Ef, and Er are the moduli of the composite, fiber, and resin, is the volume fraction of fiber, A is the average aspect ratio of the fiber, and W is the maximum packing fraction. Application of the equation is limited to small strains. (Natural fibers, plastics and composites. Wallenberger FT, Weston NE (eds). Springer, New York, 2003 Murphy J (1998) Reinforced plastics handbook. Elsevier Science and Technology Books, New York Engineering plastics and composites. Pittance JC (ed), SAM International, Mate-rials Park, OH, 1990) L... 

Chiou, J., "Finite Element Analysis of Large Strain Elastic-Plastic Solids", Ph.D. Dissertation, Dept, of Mechanical Engineering, Univ. of Minnesota, 1987. 

Strained in Verton RF-700-10 HS LNP flexure Engineering Plastics Filler 50% Long glass fiber ... 

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Strained in flexure Maranyl A127HS LNP Engineering Plastics Specimen Type V tensile specimen, heat stabilized... 

Isooctane (cont) with 15% toluene modified Fuel C 85 82 30 9 Data from SPE ANTED 1991 Conference Proceedings 97.7 Strained in flexure Maranyl PDX-R-86474 LNP Engineering Plastics Specimen Type V tensile specimen, heat stability, toughened... 

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