Ceramic mechanical testing, standardization

Such professional organizations as ASME and ASTM are taking the lead in developing die codes, specifications, and test standards for CMCs in nuclear applications. ASTM Committee C28 on Advanced Ceramics has a particular focus on mechanical test standards for CMCs. Specifically, ASTM Subcommittee C28.07 has published eleven standards for CMCs (e.g., tensile, flexure, shear, compression, creep, fatigue, etc. 

However, not only are there are no commonly-accepted design methodologies for tubular components comprised of advanced composites, at this time there are almost no mechanical test standards for any of these properties of tubular geometry ceramic composite components. In particular, for CMC tubes there is one standard for axial tensile strength that has been approved and published by ASTM as C1773-13 Standard Test Method for Monotonic Tensile Behavior of Continuous Fiber-Reinforced Advanced Ceramic Tubular Test Specimens at Ambient Temperature. ... 

Because there is no precedent for using ceramic composites in a nuclear reactor, standard test procedures will be established to qualify ceramic composites for nuclear reactor applications. In order to use SiCf/SiC in applications of structural components, it is necessary for well-established testing standards and material codes to be in place. CMCs have different mechanical behaviors than those of organic matrix composites and monolithic ceramics. Thus, new test methods are required. Some standards for the thermomechanical properties of CMCs already exist, as summarized in Table 12.9. 

European prestandard, prTS 843-9, Advanced Technical Ceramics - Mechanical Properties of Monolithic Ceramics at Room Temperature, Part 9 Method of Test for Edge-Chip Resistance, European Standard Committee TC 184, Brussels, 2009. 

ASTM C1624-05. (2010a) Standard Test Method for Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Single Point Scratch Testing, American Society for Testing Materials. 

Because some mechanical properties depend on how the material was tested, it is important and necessary to establish specified test methods. Standard test methods have been adopted for ceramics. In the United States ASTM International (originally the American Society for Testing and Materials, ASTM) is the primary organization developing standards for materials testing. ASTM Committee C-28 on Advanced Ceramics has completed several standards and ones related to mechanical properties and testing are listed in Table 16.1. Specialized subcommittees work on specific areas within the field of advanced ceramics. Coimnittee C28.01 is involved with standards related to mechanical properties and performance of monolithic ceramics. Committee C28.02 deals with reliability issues. The National Institute of Standards and Technology (NIST) has established several free databases that list mechanical properties of ceramics. 

TABLE 16.1 ASTM Standards on Mechanical Properties and Testing of Ceramics... 

As with other mechanical properties there are standard tests to measure wear resistance. The main method is described in ASTM G99, which uses a pin-on-disk apparatus. This test is used to measure sliding wear of ceranucs and ceramic coatings. 

High temperature mechanical characterization was performed on the PAIC compositions with Al/Si = 0.05 and 0.1. The elastic modulus has been measured in air at various temperatures between 800 and 1400°C by four point bend tests (40 X 20 mm) with a 0.2 mm min deformation rate. E has been calculated, through the standard equation valid for rectangular bars, by measuring the displacement with a LVDT. All the ceramic samples obtained by pyrolysis at 1000°C have been pre-annealed at 1400°C for 1 h in argon atmosphere, before the high temperature tests. This treatment lead to the crystallization of microcrystalline pSiC with a minor amount of aSiC. Aluminum atoms are present both as a solid solution of AI2OC in aSiC and in the residual amorphous phase. 

Quinn, G.D., Baratta, F.I., and Conway, J.A., Commentary on U.S. Army Standard Test Method for Flexural Strength of Fligh Performance Ceramics at Ambient Temperature, AD-A160 873, AMMRC 85-21, Army Material and Mechanics Research Center, Watertown, MA 02172-0001,1985. 

Until now, the Weibull distribution function and the ideas sketched above have formed the basis of the state-of-the-art mechanical design process for ceramic components [2-4]. Consequently, the strength testing [82-84] of ceramics and the determination of Weibull distributions have become standardized [6, 85-87]. 

European Standards Committee, Advanced Technical Ceramics - Methods of Test for Ceramic Coatings — Part 3 Determination of Adhesion and Other Mechanical Failure Modes by a Scratch Test, European Standard prEN 1071-3, March 5, 2001. 

R. W. Rice. Ceramic Fracture Features, Observations, Mechanisms and Uses, Fractography of Ceramic and Metal Failures, ASTM STP 827-American Society for Testing and Materials, Philadelphia, 1984, pp. 1-103. G. D. Quinn, J. F. Swab, and M. J. Slavin. A Proposed Standard Practice for Fractographic analysis of Monolithic Advanced Ceramics. MTLTR 90-57, Nov. 1990. 

Ceramic materials are expected to be applied to the structural parts, especially to tribological application, as they have high hardness and high elastic constants. For this application, it is important to know the properties of mechanical behavior on the surface of ceramics. Instrumented indentation is one of the tests that can explain the mechanical properties on the surface, as it expresses the relation between the penetration depth of the indenter and the applied force.For metallic materials, the standard test method in instrumented indentation is already published. We have tried the instrumented indentation tests on ceramic materials. Figure 1 is a typical example of the loading-unloading curve by this test on alumina ceramics. 

I. Bar On, G. D. Quinn, J. A. Salem, andM. J. Jenkins, Fracture Toughness Standard Test Method C 1421 99 for Advanced Ceramics, pp. 315 335 in Fatigue and Fracture Mechanics, Vol. 32, ASTM STP 1406, ed. R. Chona, American Society for Testing and Materials, West Conshohoken, PA, 2001. 

There are important issues that must be discussed before presenting composite properties. The traditional structural materials are primarily metal alloys for most of which there are industry and government standards. The situation is very different for composites. Most reinforcements and matrices are proprietary materials for which there are no standards. In addition, many processes are proprietary. This is similar to the current situation for most polymers and ceramics. The matter is further complicated by the fact that there are many test methods in use to measure mechanical and physical properties. As a result, there are often conflicting material property data in the usual sources used by engineers, published papers, and manufacmrers literature. The data presented in this chapter represent a carefully evaluated distillation of information from many sources. However, in view of the uncertainties discussed, the properties presented in this chapter should be considered approximate values. 

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