QuickTalk 12 - COMPOSITE NEWS
- Category: Q-Talk Articles
- Published: Monday, 31 October 1983 06:11
- Written by Jim Masal
- Hits: 1944
It may be confirmed by the time you read this that certain Chinese workers have been trained at Mojave to build Q2's overseas. These ready-to-fly aircraft will be available to U.S. customers. Expected price is around $25,000 per copy.
Some time ago, Beech Aircraft Company set up a low-profile 'skunk-works' to develop a new composite technology aircraft. Their result was recently unveiled at the NBAA convention in Dallas. Called the "Starship-1", its appearance resembles a Long-Eze with a 10-place cabin. Not surprisingly, the designer was Burt Rutan and the prototype was built by his company, Scaled Composites Inc. This possible successor to the King Air features twin pusher turboprop engines and a variable sweep canard. Beech's entry into the composite arena is viewed as a significant technical gamble by a "Big Three" manufacturer. Certifications procedures may prove more tedious than usual due to the unfamiliarity of many FAA officials with composite testing.
Alert Oshkosh visitors this year may have noticed what appeared to be corrugations in the upper canard surface of the prototype Dragonfly. Apparently the fuselage was sinking closer and closer to the ground with time resulting in reduced prop clearance. Improper post-curing is suspected. The "tin goose" appearance developed after trying to recure to the original anhedral before Oshkosh. Builders should take heed and not fail to post-cure.
/The following report was forwarded to us by Paul Schnepp and appeared in a recent issue of the London Financial Times.-Ed./
Officials at ICI Petrochemical in Welton, England were spending time in California this summer drumming up business for composites made of newly discovered resins reinforced with carbon fiber. The resins are thermoplastics, inherently far tougher than the thermosetting resins such as epoxies previously used in composites. PEEK (polyether etherketone) was first made in the laboratory only in 1979. Last year ICI sole 25 tons of PEEK reinforced with 50 percent by volume of carbon fiber to make a composite tougher, yet light, than aluminum alloys. It plans to scale up production to 1000 tons or more per year, plus add a U.S. plant.
Composites of PEEK are resistant to anything short of sulphuric acid by way of corrosives, and highly resistant to damage. Their toughness comes from the micro-structure of the composites. The bonding between fiber and thermoplastic is completely different from the bonding between fiber and thermosetting resin. The crystallinity of the resin continues into the surface of the fiber, producing a much tougher bond. The composite can confidently be assumed to retain its strength until there is visible evidence of damage, in contrast to metals, which can suffer an invisible loss of strength through fatigue. One dramatic demonstration of the toughness of the composite is the fact that gear blanks can be punched from sheet metal. If this is attempted with a composite based on a thermosetting epoxy resin, the teeth shatter to powder.
Lynette Downey of Cupertino, California sent us a copy of the SAFE-T-POXY precaution brochure printed by Applied Plastics Inc. that was mentioned in Issue #10. The eight-page article is well written and focuses on many of the conditions faced by homebuilders. There are several items that deserve repeating.
First, it is not recommended that barrier creams be relied upon to protect against dermatitis (reaction). Second, cheap vinyl or polyethylene gloves provide little protection because of the permeability of low molecular weight solvents. Also, never use barrier cream under tightly stretched gloves. Third, the use of steroid creams for inflammatory relief MAY prove effective on small infected areas, but they should not be used on large skin areas or for prolonged periods. These creams will not prevent recurrence of irritation if sensitivity has already been acquired. Fourth, with respect to inhaled contaminants, wear an organic mask whenever sanding or making a layup. Also be conscious of good ventilation during these operations. Avoid breathing high vapor pressure solvents, such as acetone. Fifth, never dispose of SAFE-T-POXY or any resin-containing material in a fire where the products can be inhaled. Sixth, once a person has become sensitized, a minor exposure is all that is needed to provoke a reaction.
Unfortunately, the recommendations by Applied Plastics do not include any "Secret Hints" that are not immediately known to the veteran compositer: 1) Do not permit resin or hardener to remain in contact with skin. 2) Wear good gloves with cotton gloves underneath. Launder cotton gloves daily. 3) Do not use harsh solvents or soaps to clean hands. 4) Wear a dust respirator when sanding. 5) Make layups under good ventilation conditions and wear an organic vapor mask. 6) At day's end, wash hands thoroughly with soft soap and apply an emollient lotion. 7) Get medical attention if problems arise.
As you can gather, the most important item is to practice intelligent hygiene and to always be alert for possible contamination sources. As many unfortunate builders can testify, once a sensitivity problem occurs, it is usually too late to begin careful work habits.
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