INVESTIGATION INTO THE CHARACTERISTICS AND PROPERTIES OF WHISKERS, FIBERS, AND THIN FILMS; INVESTIGATION OF FIBROUS BREAK IN 7075-T6 ALUMINUM ALLOY EXTRUDED CHANNEL SECTION.
NAVAL AIR ENGINEERING CENTER LAKEHURST NJ AERONAUTICAL MATERIALS LAB
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A recent report on an A4 inflight fire investigation revealed some interesting breaks in 7075T6 aluminum alloy extruded channel section. Two views a and b of such a break are enclosued. The shredded appearance of the break can be compared with that shown by a wooden beam which fails under torsional bending. In a, the break is fibrous whereas in b, it has a laminated appearance. Because of the high strength often associated with fine fibers of all types of materials, the Aeronautical Materials Laboratory was requested to investigate the above fibrous material from the standpoint of its origin and possible utility. A preliminary study of individual fibers indicated brittle-like behavior and usually very little bending stress could be tolerated. This is probably due to numerous surface irregularities formed by the break down of massive grains. The fibers were found to be generally large and irregular in cross section so that tension testing would be exceptionally difficult. In view of the above observations, a tension test program appeared to be unattractive and therefore was omitted. Author