Compressive modulus point

The Imass Dynastat (283) is a mechanical spectrometer noted for its rapid response, stable electronics, and exact control over long periods of time. It is capable of making both transient experiments (creep and stress relaxation) and dynamic frequency sweeps with specimen geometries that include tension-compression, three-point flexure, and sandwich shear. The frequency range is 0.01—100 H2 (0.1—200 H2 optional), the temperature range is —150 to 250°C (extendable to 380°C), and the modulus range is 10" —10 Pa. 

Fig. 44. Dependence of the 13C Tte relaxation times (yBj = 60 kHz) for PTEGDMA on the extent of cure inner CH20 ( ), end CH20 (O), CH2 (4-) and CH3 (A) for quaternary ( ), represents Tle/10. Standard errors do not exceed the bounds of the symbols. The dots represent the compression modulus, E (MPa). V indicates the vitrification point (reprinted from ref.2481 with permission)...

Hartmann already pointed out that the reducing parameter B0 is equal to the compression modulus or bulk modulus K, extrapolated to zero temperature and pressure and that T0 is related to the glass transition temperature. 

The compressibility k is the reciprocal of the compression modulus or bulk modulus of the material. This important property will be discussed in Chap. 13 (Mechanical properties of solid polymers). The application of Eq. (7.27) is restricted to polymer melts. For amorphous polymers below the melting point, the internal pressure n may be defined as well ... 

Janes, Neumann and Sethna ° reviewed the general subject of solid lubricant composites in polymers and metals. They pointed out that the reduction in mechanical properties with higher concentrations of solid lubricant can be offset by the use of fibre reinforcement. Glass fibre is probably the most commonly used reinforcing fibre, with carbon fibre as a second choice. Metal and ceramic fibres have been used experimentally to reinforce polymers, but have not apparently been used commercially. To some extent powders such as bronze, lead, silica, alumina, titanium oxide or calcium carbonate can be used to improve compressive modulus, hardness and wear rate. 

The compression of uniform samples to the point where the force exceeds the structural capacity causes it to permanently deform and essentially break (4). A typical load-deformation curve can be used to derive values for yield stress, yield strain, and compressive yield work, and depending on the linearity of the onset of compression, a compressive modulus may be obtained (4). These measurements can be used to provide an index of hardness for fats, which have been successfully correlated to the textural attributes of hardness and spreadability obtained through sensory evaluation (4). Unfortunately, these tests are destructive in nature and yield minimal information about the native microstructure of the system. 

Compression Load Perpendicular to Rise PSI At Yield Point At 10 S Deflection Compression Modulus PSI Flexural Strength PSI Flexural Modulus PSI Shear Strength PSI Shear Modulus PSI... 

Tensile or compressive modulus is the ratio of stress to strain at any point along the initial straight portion of the stress-strain (load-deformation) curve ... 

Compressive properties include compressive strength, modulus of elasticity, yield stress, and deformation beyond yield point. The ASTM procedure covers determinations of all of them. In all cases, tested specimens are loaded in compression at relatively low uniform rates of straining or loading. Compressive yield point is the first point on the stress-strain curve at which an increase in strain occurs without an increase in stress. In other words, it is the load under which the specimen starts to move continuously without an increase in the load. Also, many plastic materials will continue to deform in compression until a flat disk is produced, without breaking of the specimen. In those cases the compressive stress (nominal) increases steadily in the process, without failure of the material. Compressive strength typically has no meaning in such cases. 

The compressive strength is calculated by dividing the maximum compressive load by the original minimum cross-sectional area of the specimen. The compressive yield strength is calculated in the same manner, but instead of compressive load at break, the compressive load at the yield point is used. The compressive modulus of elasticity is calculated in the usual manner, by dividing the compressive stress taken as a point on the initial linear portion of the load-deformation curve by the corresponding strain. 

For measuring compressive modulus, the. v// ratio should not be less than 0.08. while for other tests it should not be less than 0.4. The smaller ratio for the modulus test is permitted since the strain range required for the test is so small and hence the point of buckling is unlikely to be reached. As with other ISO test methods, preferred specimen sizes (Fig. 5) arc given, which in this case arc... 

Specifications should include any specific properties required for the application, such as resilience, hysteresis, static or dynamic shear and compression modulus, flex fatigue and cracking, creep resistance to oils and chemicals, permeability, and brittle point, all in the temperature ranges to be encountered in service. 

Tensile strength at yield Tensile modulus Elongation at break Flexural strength Flexural modulus Compressive strength Compressive modulus Impact Notched Izod Unnotched Izod Chemical resistance Water absorption Thermal Melting point Tg... 

Material Total thermal expansion 70 to -323 F 70-J--323 70 Brittle point, F EXirometer points shore A Compression modulus at -323 F, psi... 

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