Significance and Use
5.1 This test method has advantages in certain respects over the use of static loading systems for measuring moduli.
5.1.1 This test method is nondestructive in nature. Only minute stresses are applied to the specimen, thus minimizing the possibility of fracture.
5.1.2 The period of time during which measurement stress is applied and removed is of the order of hundreds of microseconds. With this test method it is feasible to perform measurements at elevated temperatures, where delayed elastic and creep effects would invalidate modulus of elasticity measurements calculated from static loading.
5.2 This test method is suitable for detecting whether a material meets the specifications, if cognizance is given to one important fact in materials are often sensitive to thermal history. Therefore, the thermal history of a test specimen must be considered in comparing experimental values of moduli to reference or standard values. Specimen descriptions should include any specific thermal treatments that the specimens have received.
Scope
1.1 This test method covers the determination of the dynamic elastic properties of elastic materials. Specimens of these materials possess specific mechanical resonant frequencies that are determined by the modulus of elasticity, mass, and geometry of the test specimen. Therefore, the dynamic elastic properties of a material can be computed if the geometry, mass, and mechanical resonant frequencies of a suitable test specimen of that material can be measured. The dynamic Young's modulus is determined using the fundamental flexural resonant frequency. The dynamic shear modulus, or modulus of rigidity, is found using the fundamental torsional resonant frequency. Dynamic Young's modulus and dynamic shear modulus are used to compute Poisson's ratio.
1.2 This test method is specifically appropriate for materials that are elastic, homogeneous, and isotropic (1).2
1.3 Materials of a composite character (particulate, whisker, or fiber reinforced) may be tested by this test method with the understanding that the character (volume fraction, size, morphology, distribution, orientation, elastic properties, and interfacial bonding) of the reinforcement in the test specimen will have a direct effect on the elastic properties. These reinforcement effects shall be considered in interpreting the test results for composites.
1.4 This test method shall not be used for determination of Poisson’s ratio of anisotropic materials.
Note 1: For anisotropic materials, Poisson’s ratio can have different values in different directions. Due to the lack of symmetry in anisotropic materials, the elasticity tensor cannot be reduced to only two independent numbers, and the simplified relation between E, G, and µ is not valid.
1.5 This test method should not be used for specimens that have cracks or voids that are major discontinuities in the specimen.
1.6 The test method should not be used when materials cannot be fabricated in a uniform rectangular or circular cross section.
1.7 An elevated-temperature furnace and cryogenic chamber are described for measuring the dynamic elastic moduli as a function of temperature from –195 °C to 1200 °C.
1.8 This test method may be modified for use in quality control. A range of acceptable resonant frequencies is determined for a specimen with a particular geometry and mass. Any specimen with a frequency response falling outside this frequency range is rejected. The actual modulus of each specimen need not be determined as long as the limits of the selected frequency range are known to include the resonant frequency that the specimen must possess if its geometry and mass are within specified tolerances.
1.9 There are material-specific ASTM standards that cover the determination of resonant frequencies and elastic properties of specific materials by sonic resonance or by impulse excitation of vibration. Test Methods C215, C623, C747, C848, C1198, C1259, and C1548 differ from this test method in several areas (for example; specimen size, dimensional tolerances, specimen preparation). The testing of these materials shall be done in compliance with these material specific standards. Where possible, the procedures, specimen specifications, and calculations are consistent with these test methods.
1.10 A separate standard, Test Method E1876, governs determination of dynamic elastic moduli by impulse excitation instead of sonic resonance.
1.11 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.12 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.13 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
