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testing tech testing tech composites testing: the continUing stanDarDs DiLemma ment will regain its vitality. Instead, the oft-used approach, currently, is to select a speci���c standard test method for the particular design application at hand and strictly follow it. And because there often are multiple test methods available to measure a particular property, many different standards are currently being followed and many methods are used, with little or no attempt at harmonization. In the global aerospace industry, most of the testing standards in use at present are derivatives of U.S. aerospace industry procedures formalized over the years by ASTM International (West Conshohocken, Pa.). That is, most of the aerospaceoriented standards (e.g., DIN, EN, prEN, ISO) have been taken from the ASTM standards, typically with only minor changes. Unfortunately, these minor changes are the source of many current major problems. A test ���xture developed for one standard will not necessarily satisfy the requirements of another standard. And n May 2007, this column was devoted ASTM itself caused many of these probto the standardization of test methlems when its committees developed ods and the need for same. A detailed these test methods by insisting on using discussion of the evolution of standards ���soft conversions��� of dimensions from the was presented, and it is, perhaps, well U.S. Customary (English) units when they worth rereading today. That column was calculate the S.I. (metric) unit values for followed in the next issue (July 2007) by their ���dual unit��� standards. That is, rather a discussion of attempts to achieve glothan using direct (exact) converbalization and harmonization sions of the U.S. Customary units (see ���Learn More,��� p. 11). More many testing laboratories are forced to to S.I. units (hard conversions), than ���ve years have passed since they have mandated the practice these articles were written. It���s have two (or more) test ���xtures available to of arbitrarily rounding convertime for a progress report. perform the same test. sions to convenient (hence, the Globalization ��� the spread of name "soft") even numbers. For composites technology, includAbout 10 years ago, it was recognized example, a 0.25-inch diameter loading ing composites testing, independent of geographical and political boundaries ��� that the answer to this question was ���not or support cylinder on a ���exure ���xture has exploded during the past ���ve years. necessarily.��� The need for harmonization becomes a 6-mm diameter cylinder in The commercial aircraft industry has led of test methods was acknowledged, and the metric version of the standard. It has the way, driven particularly by The Boeing some preliminary work was conducted been well demonstrated, both analyticalCo. (Chicago, Ill.) and Airbus (Toulouse, during the next few years. This included ly and experimentally, that this small difFrance). These major commercial air- gathering experimental data from the lit- ference in size has no measurable effect frame manufacturers have involved many erature and generating new data to permit on the experimental results obtained. subcontractors around the world in de- direct comparisons of selected test meth- Nevertheless, the strict follower of the veloping the new materials and processes ods. This was a time-consuming, dif���cult metric standard will not use an available they need. Thus, they are spreading these and expensive activity. Unfortunately, the test ���xture that has 0.25-inch diameter advanced technologies around the world. initial enthusiasm for this approach and cylinders. Another example is the Open-Hole This has given many individuals, com- the pursuit of harmonization has faltered, panies, countries and special-interest with little sign, at present, that the move- Compression Test Method (ASTM Dr. Donald f. adams is the president of Wyoming test fixtures inc. (salt Lake city, Utah). he holds a Bs and an ms in mechanical engineering and a ph.D in theoretical and applied mechanics. following a total of 12 years with northrop aircraft corp., the aeronutronic Div. of ford motor co., and the rand corp., he joined the University of Wyoming, directing its composite materials research group for 27 years before retiring from that post in 1999. Dr. adams continues to write, teach and serve with numerous industry groups, including the test methods committees of astm and the Composite Materials Handbook 17. I 10 | groups worldwide a strong opportunity to exert their individual opinions and biases on the current technology. That is, we now have more concepts than ever about the best way to proceed. This de���nitely includes test methods. Although many of these concepts will fall into disuse as they are eventually shown to be de���cient or ineffective, some will become new standards or additions to existing standards. In summary, globalization has led to much new research activity on an international scale in a relatively short time period, and as such, it has been a very favorable development. Long before globalization, however, various groups around the world had developed their own standard methods for testing composites. These were discussed in my May 2007 column. As the composites industry has become a more global enterprise, these groups were no longer isolated and came into increasing contact with one another. This led to recognition of the need for harmonization. That is, the groups sought to answer this question: When two (or more) different test methods follow different procedures to obtain data on the same material property, do the different methods produce statistically equivalent results, such that the methods can be used interchangeably? high-performance composites