Density compression strength

This Navy specification covers a single class of foam, nominal density 2.0 Ib/ft rigid unicellular polyurethane foam, and the materials required for preparation by the foam-in-place technique. Requirements cover density, compressive strength, volume change after heat aging, humidity aging, compressive set, unicellularity (% open cells, max.), oil resistance, and fire resistance. 

Processing production of coal sample and physical mechanic parameters test are in strict accordance with the provisions of Measurement method of coal and rode physical and mechanical properties (GB/T 23561-2009), and Measurement method of coal seam impact tendency classification index (MT/T 866-2000). The experiment determined natural apparent density, compressive strength, consistent coefficient, elastic modulus, deformation modulus, wave velocity, rock burst energy index, elastic energy index, dynamic failure time, and other parameters. The determination results as shown in Table 1. 

Since every component used in a cell (GDL, catalyst layer, bipolar plate, matrix layer, etc.) is critical for the operation of the cell stack, these components have to be within a very tight specification and meet defined key product characteristics. This requires the implementation of a robust quahty control system. For example, substrates in PAFCs have to be checked for porosity, IR, thermal conductivity, thickness, density, compressive strength, flex strength, etc. All of these quality checks impart cost to the substrate. Ability to integrate these measurements into... 

Density and polymer composition have a large effect on compressive strength and modulus (Fig. 3). The dependence of compressive properties on cell size has been discussed (22). The cell shape or geometry has also been shown important in determining the compressive properties (22,59,60,153,154). In fact, the foam cell stmcture is controlled in some cases to optimize certain physical properties of rigid cellular polymers. 

Tensile strength and modulus of rigid foams have been shown to vary with density in much the same manner as the compressive strength and modulus. General reviews of the tensile properties of rigid foams are available (22,59,60,131,156). 

The blue-black Hon oxide formed in this process fills some of the interconnecting porosity and much of the surface. Hence the density is increased, resulting in higher compressive strength. Furthermore, the oxide coating increases hardness (qv) and wear resistance. 

The success of the compaction operation depends pardy on the effective utilization and transmission of appHed forces and pardy on the physical properties and condition of the mixture being compressed. Friction at the die surface opposes the transmission of the appHed pressure in this region, results in unequal distribution of forces within the compact, and hence leads to density and strength maldistribution within the agglomerate (70). Lubricants, both external ones appHed to the mold surfaces and internal ones mixed with the powder, are often used to reduce undesirable friction effects (71). For strong compacts, external lubricants are preferable as they do not interfere with the optimum cohesion of clean particulate surfaces. Binder materials maybe used to improve strength and also to act as lubricants. 

In addition to chemical analysis a number of physical and mechanical properties are employed to determine cemented carbide quaUty. Standard test methods employed by the iadustry for abrasive wear resistance, apparent grain size, apparent porosity, coercive force, compressive strength, density, fracture toughness, hardness, linear thermal expansion, magnetic permeabiUty, microstmcture, Poisson s ratio, transverse mpture strength, and Young s modulus are set forth by ASTM/ANSI and the ISO. 

Armor. Sihcon carbide is used as a candidate in composite armor protection systems. Its high hardness, compressive strength, and elastic modulus provide superior baUistic capabihty to defeat high velocity projectile threats. In addition, its low specific density makes it suitable for apphcations where weight requirements are critical (11). 

Like the modulus, the tensile and compressive strengths depend mainly on the density (Fig. 26.6). The strength parallel to the grain varies linearly with density, for the same reason that the axial modulus does it measures the strength of the cell wall, scaled by the fraction of the section it occupies, giving... 

Fig. 26.6. The compressive strength of wood depends, like the modulus, mainly on the relative density p/p,. That along the groin varies os p/p, that across the groin varies os...

In the 1990s this approach became more common in order to ensure sufficient compressive strength with the trend to lower bulk densities. Furthermore the proportion of SAN to polyol has been increased to about 40%. This may lead to serious stability problems and care must be taken to control the size and distribution of the particles and prevent agglomeration. Polymer polyols using polystyrene as the polymer component have recently become available (Postech-Shell) and are claimed to exhibit good stability, low viscosity and less discolouration as well as providing price advantages. 

Fig. 5. The variation of CBCF compressive strength with density for samples maehined in the molding direetion. Reprinted from [10], eopyright 1985 The American Ceramics Society, with permission.

During the temperature ramp period, pressure is applied. How much pressure is applied depends on the adhesive and the type of assembly. Honeycomb assemblies are limited by the compression strength of the honeycomb core, so cure pressure is typically limited to 50 psi for aluminum core of standard density. Metal to metal assemblies can withstand higher pressures and usually have fewer bondline voids when cured at higher pressures. Metal-to-metal assemblies bonded with standard modified epoxies are cured at 90 psi. 

Material Density (g/cm 1 Coating weight (kg/m ) 0-025 mm thickness Brinell hardness Ratio of contraction stresses in sprayed deposits 0-51 mm thick Compressive strength (stress to collapse) (MN/m )... 

Foam Density lb./ft.3 Glass Microballoons Epoxy Macroballoons Uniaxial Compressive Yield Strength, psi Hydrostatic Compressive Strength, psi Method of Preparation Resin System... 

A1 from 100%, 9.0 0.5% (6) moisture content by the Karl Fischer method, 0.5% max (7) compressive strength, by pressing to 30000psi with subsequent measurement of pellet diam and height to 0.001 inch, lOOOOpsi min (8) density, by wt and vol measurement, 1.8l4g/cc min ... 

The cast density of Pentolites does not vary appreciably with blend compn. 50/50 Pentolite (hereafter to be referred to simply as Pentolite) has a cast density of 1.63—1,67g/cc (Ref 8a), while 10/90 Pentolite has a cast density of 1.60 g/cc (Ref 12). The density of pressed Pentolite lies between 1.60 and 1,65g/cc. Since Pentolites are blends (no compound formation) they are soluble in the same solvents as their constituents (PETN TNT). Pentolite has a compressive strength of 2000—2200psi at 1.68g/cc (Ref 12)... 

Density of soil in place by the sleeve method Unconsolidated undrained compressive strength of cohesive soils in triaxial compression... 

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