1212 Design Codes and Databases

The meaning of the term design code is not generally well understood. As used in the following discussion design code is not a design manual (i.e., a "cookbook" design procedure resulting in a desired component or system. [3]. Instead, design codes are widely accepted but general rules for the construction of components or systems where safety is important. A primary objective is the reasonably certain protection of life and property for a reasonably long safe life of the design. Although needs of the users, manufacturers, and inspectors are recognized, the safety of the design can never be compromised.

By not imposing specific rules for design, the code allows flexibility for introducing new designs as required for performance, efficiency, usability, or manu-facturability while still providing constraints for safety. The code must be wide ranging, incorporating figurative links between materials, general design (formulas, loads, allowable stress, permitted details), fabrication techniques, inspection, testing, certification by stamping and data reports, and finally quality control to ensure that the code has been followed. Thus, implicit in the design codes may be many of the standards previously discussed for materials testing, characterization, and quality control. In addition, unlike standards that provide no rules for compliance or accountability, codes require compliance through documentation, and certification through inspection and quality control.

A logical outcome of design codes is the incorporation of databases of material properties and performance "qualified" for inclusion in the code. These data are "qualified" because they have been attained through testing per the statistical requirement of the code as well as per the standards indicated in the code. Qualified databases often require a minimum numbers of test for (1) a particular batch of material and (2) multiple batches of material. In addition, databases may include primary summary data (e.g., mean, standard deviation, and numbers of tests) along with secondary data from the individual tests. Some databases may contain only numerical information while others may include graphical information (e.g., stress-strain curves, temperature profiles, or test specimen geometry). Databases are increasingly in electronic form to speed data retrieval and many are even web-based to provide instant access and frequent updatability.

Design codes and their databases may even be backed as legal requirements for implementing an engineering design [e.g., certification and compliance with the American Society of Mechanical Engineers (ASME), Boiler and Pressure Vessel Code [4] is a legal requirement in 48 of the 50 United States]. At present there are no national or international design codes allowing continuous fiber-reinforced ceramic composites (CFCCs) in any type of design. This situation may be hampering material utilization since designers cannot use a material directly in new designs but instead must (1) show evidence that the material meets the requirements of the code and (2) obtain special permission to used the material in the code design. In addition material development is impaired since without a demand for a new material, there is no incentive for further refinement.

This chapter concentrates on standards and codes for advanced materials. First, national and international standards bodies are briefly reviewed keying on important mechanical, thermal, and physical aspects that require standardization. Next, a similar brief review of national and international design codes and evolving databases for advanced materials is presented. Finally, the summary and conclusion section contains successes, lessons, and future directions for standards and codes for advanced materials.

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