At rightis theAvtek400experimentalbusinessairplane,atwinturbopropthatwasintroducedtoflighttestlastSeptember.Developedli_AvtekCo_oration,Camarillo,California;theai_!aneisdistinguisiiedbythefactthatitsai.rframeis madeentirelyof comp0siU_materiaisiWhi(:h

.........

A number of military and commercial aircraft alreadyin operational: service have components made :ofcomposites, but the Avtek 400 is among the first all-composite aircraft. Increasing use of composites inairframes is a trend of the future because of the

sin_:_ular_,advanta_es_, they offer in comparison withimproved performance, dramatically

lower weight and, in some cases, reduced cost.

The principal materials used in the Avtek 400 areKevlar® aramid fiber and Nomex® aramid, both

developed by The Du Pont Company, Wilmington,Delaware, a pioneer in development and manufactureof materials for composites. Kevlar is a fiber that,pound for pound, is five times as strong assteel.Nomex is Du Pont's trade name for a family of highstrength, high temperature resistant aramid :sheetstructures, staple fibers :and filament yarns. More than70 percent of the Avtek 400is made of honeycomb ofNomex sandwiched between skins of Kevlar fiber.

Honeycomb is a series of cells grouped togetherto form a panel similar in appearance to a cross-sectional slice of a beehive. It is 90 to 99 percent openspace, hence extremely light; when the core of Nomexis bonded between two surfaces, the resultingsandwich structure has exceptionally highstrength-to-weight and rigidity-to-weight ratios.

Use of Kevlar and Nomex in the Avtek 400 combine

to give the airplane a light, tough structure that has amaximum weight of only 5,500 pounds, about half theweight of a metal airplane of comparable size andperformance. Composites can be molded into manyaerodynamic shapes, eliminating most of the rivetsand fasteners required in metal construction. The

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Avtek400ismadeof48molds.Themiddlephoto,oppositepage,showstheaft sectionandverticalstabilizer;atlowerleft istheforwardsection.

NASA'sLangleyResearchCenterisamongtheworld'sleadingorganizationsforresearchoncompositestructures.Langleyhasconductedextensiveinvestigationandtestonapplyingcompositesto spacevehicles,commercialaircraft,militaryaircraftandhelicopters;suchworkincludedapplicationtestingcomponentsof KevlarthatassistedDuPontin thecompany'sownadvancementofitsproduct.Specifically,Langleyconductedresearchinsupportof SpaceShuttleuseofpressurebottlesfilament-woundwithKevlar,aweightsavingmeasure.Thatdevelopmentledto useofsimilarbottlestoactivateescapeslidesin theBoeing747and757jetlinersatasavingof20poundsperbottle.A Langley/LockheedCorporationexperimentalprograminvolvinguseof composites--includingKevlar--ontheL-1011transportfosteredadoptionoffiberreinforcedpartsonsuchnewaircraftastheBoeing757and767,bothof whichemploysignificantamountsofhybridstructurecomposedofKevlar,carbonandepoxy.

Thegrowinguseof compositesin aerospace

applicationsisexemplifiedbyDuPontstatistics.In1983,DuPontshipmentsofKevlarandNomextotheaerospaceindustrywereusedto producecompositepartsworthmorethan$500million;thecompanyestimatesthatby1988it will beshippingthreetimesasmuchfor aerospaceapplicationsalone.

Useof compositesisrapidlyspreadingto othermarkets--boats,for instance.A largepercentageof smallpleasureandcommercialboatsalreadyincorporatecompositesandthetrendisbeingextendedto largervesselstotakeadvantageof theweightreductionandperformancegainscompositesoffer.Shownbelowis the80-footyachtKialoa, whosehull is reinforced with Kevlar fiber; the fiber's

toughness increases the hull's resistance to damageand Kevlar's lightness provided new design latitude indistributing weight for maximum sailing efficiency.Du Pont composites are also finding increasing use insuch other applications as transportable militaryshelters, components of automotive vehicles,protective apparel for people in hazardousprofessions, marine-use ropes and cables, anda broad variety:of industrial uses.

®Kevlar and Nomex are registered trademarks of E.I. Du Pont

de Nemours & Company (Inc).

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