Flexural modulus measurement

Precision of flexural modulus measurements is usually good. ASTM D 790-97 lists examples for six different plastics tested in six different laboratories. For within-laboratory tests, standard deviations of the average were 0.8 0.6% of the principal figure, and for between-laboratory tests, standard deviations of the average were... 

Fig. 9 shows the flexural Young modulus of our different composites Fig. 10 shows the mechanical dynamical flexural modulus measured at room temperature in the range of 500 c.p.s. in the case of untreated and SIC treated beads. The theoretical curves (continuous lines) were obtained with the parameters Vm = 0.38, Eg =... 

Figure 4.Three point bending test results for PLLA and PLLA/TCP samples flexural strength,strain at flexural strength and strain at break, flexural modulus measured after various biodegradation periods.

Another resonant frequency instmment is the TA Instmments dynamic mechanical analy2er (DMA). A bar-like specimen is clamped between two pivoted arms and sinusoidally oscillated at its resonant frequency with an ampHtude selected by the operator. An amount of energy equal to that dissipated by the specimen is added on each cycle to maintain a constant ampHtude. The flexural modulus, E is calculated from the resonant frequency, and the makeup energy represents a damping function, which can be related to the loss modulus, E". A newer version of this instmment, the TA Instmments 983 DMA, can also make measurements at fixed frequencies as weU as creep and stress—relaxation measurements. 

Elastomer samples are cast in molds, the size and shape of which depend on its purpose. Samples for physical properties can be produced using a custom-made book mold designed to create a thin sheet (0.1 in.) containing premolded test parts, such as those for die-C tear, flexural modulus, and so on. Alternatively, a flat plaque mold may be used to create a 6 x 6 x 0.1-in. sheet from which may be cut samples for testing. Thicker samples for hardness measurements may... 

Tensile moduli were measured from standard dog-bone samples (2.0 mm thickness, 4.7 mm width, and 22.0 mm gauge length) in a Model 1122 Instron. Flexural modulus was determined using a testing apparatus which consists of two aluminium/steel pieces attached to the Instron which is fitted with a tensile load cell. This device effectively performs an inverted three-point bend the two side bars remain stationary above the sample as the central bar below the sample moves upward. Flexural samples measured ca. 52.0 x 1.7 x 13.1 mm and were tested using a 25.4 mm span (distance between the two side bars). Crosshead speed (CHS) for both flexural and tensile testing was 1.0 mm/min. 

The variation of the damping factor (tan 5) with temperature was measured using a Polymer Laboratories Dynamic Mechanical Thermal Analyzer (DMTA). The measurements were performed on the siloxanfe-modified epoxies over a temperature range of — 150° to 200 °C at a heating rate of 5 °C per minute and a frequency of 1 Hz. The sample dimensions were the same as those used for flexural modulus test specimens. 

Flexural Properties. Both flexural modulus and flexural strength values were obtained. These values were measured at 23 °C and also over a range of temperatures for the MBAS polymer (see Figure 4). In the flexural tests, a molded bar is tested as a simple beam, the bar resting on two supports, and the load is applied midway between. The test is continued until rupture or 5% strain, whichever occurs first. The test fixture is mounted in a universal tester, and the tester is placed in an appropriate temperature environment. 

Flexural modulus A measure of the strain imposed in the outermost fibres of a bent specimen. 

Fig. 6. Values of back-calculated modulus for the joints as a function of measured crack length. (Note that the known value of the flexural modulus, E, of the substrate was 126GPa)...

Due to the higher flexural modulus of SMC, such parts are molded with the thickness reduced to. 100 Inch. Thickness reductions are projected for all materials, however such speculative material use reduction measures were not considered. 

Elongation and flexural modulus were measured on an Instron tester model number 1125 according to ASTM D-638 and ASTM D-790 tests respectively. 

The Izod notched impact strength (ASTH D-256) and the flexural modulus (ASTM D-790) of the obtained products were measured. For a number of specially selected samples, the dynamic mechanical properties were determined. 

Flexural Modulus. Figure 5 shows flex modulus values at 23 °C measured parallel and perpendicular to flow. The nonreinforced urethane polymer has a value of about 50,000 psi. Columns B and C show the results obtained with 8.5% and 20% loadings of milled glass fibers, respectively. Column D shows results obtained with 3.5% loadings of 1/8 chopped Integral strands. The flex modulus increased by about 20%. Column E shows data for 13.4% integral chopped strands the increase was more than 240% of the original... 

Polystyrene blended with 2% of polymer 3 was injection molded into 1/8-inch wide flex and tensile bars for mechanical measurement. It had no effect on the flexural modulus of polystyrene, but a significant improvement in the initial modulus with a concomitant sacrifice in the maximum strength was obtained. Weak cross-linking of polystyrene by polymer 3 through aryl-aryl interaction might be responsible for the high initial modulus. 

Flexural modulus is a convenient measure of composite stiffness. Fillers can con-tribute significantly to a stifmess increase. 1 he... 

R.H. chamber. These data were generally close to the room temperature immersion results, and with one exception are not reported here.) The flexural modulus of the specimen was also measured at the time of weighing, since the absorbed water acted to plasticize the cured resin. 

Physical Property Measurements. Flexural modulus and strength were measured according to ASTM Method D-790. Impact resistance was measured by the Izod notch ASTM D-256, and Rockwell Hardness... 

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