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WK91 Practice for Strain Controlled Thermomechanical Fatigue of Continuous Fiber-Reinforced Advanced Ceramics

Date Initiated: 02-07-2003
Date Deletion Requested: 08-24-2007

1. Scope

1.1 This practice covers the determination of thermomechanical fatigue (TMF) behaviour and
performance of of continuous fiber-reinforced advanced ceramic composites (CFCCs) under uniaxially loaded strain-controlled conditions. A "thermomechanical" fatigue cycle is here defined as a condition where uniform temperature and strain fields over the test specimen gage section are simultaneously varied and controlled. This practice builds on experience and existing standards in tensile testing CFCCs at ambient temperatures and addresses various suggested test specimen geometries, specimen fabrication methods, testing modes (force, displacement, or strain control), testing rates and frequencies, allowable bending, and procedures for data collection and reporting. This practice is intended as a guide for TMF testing performed in support of such activities as materials research and development, mechanical design, process and quality control, product performance, and failure analysis. While this practice is specific to strain-controlled testing, many sections provide useful information for force-controlled or stress-controlled TMF testing. This practice is limited to test specimens and does not apply to axial TMF tests of full scale components, parts, structures or consumer products (that is, machine elements with nonuniform or multiaxial stress states).
1.2 This practice allows for any maximum and minimum values of temperature and mechanical strain, R, ratio, and temperature-mechanical strain phasing, with the restriction being that such parameters remain cyclically constant throughout the duration of the test. No restrictions are placed on environmental factors such as pressure, humidity, medium, and others, provided that they are controlled throughout the test, do not cause loss of or change in test specimen dimensions in time, and are detailed in the results report.
1.3 This practice applies primarily to advanced ceramic matrix composites with continuous fiber
reinforcement: unidirectional (1-D), bi-directional (2-D), and tri-directional (3-D) or other multidirectional reinforcements. In addition, this practice may also be used with glass (amorphous) matrix composites with 1-D, 2-D, 3-D, and other multi-directional continuous fiber reinforcements. This practice does not directly address discontinuous fiber-reinforced, whisker-reinforced or particulatereinforced ceramics, although the methods detailed here may be equally applicable to these composites.
1.4 The values stated in SI units are to be regarded as the standard and are in accordance with
IEEE/ASTM SI 10 Standard.
1.5 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 and
health practices and determine the applicability of regulatory limitations prior to use. Refer to
Section 7 for specific precautions.