ISOGRID DESIGN HANDBOOK - NASA

1 NASACONTRACTORREPORTNASACR-124075 REVISIONAISOGRIDDESIGNHANDBOOKMcDonnellD ouglasAstronauticsCompany5301 BotsaAvenueHuntingtonBeach,Ca92647 February1973[NASA-CR-12_075)150 GRIDDESIGNHANDBOOK(McDonnell-DouqlasAstr onauticsCo.)222pHC$ .) ,GRIDDESIGNHANDBOOKMDCG4295 APREPAREDBY,V1 CDONNELLDOUGLASASTRONAUFIL;SCO_.,1 PANYFOR:NASAMARSHALLSPACEFLIGItTCEN] FOREWORDT hisprogram,thedevelopmentoftheisogriddes ignhandbook,wasconductedbytheMcDonnellDo uglasAstronauticsCompanyatHuntingtonBeac h,Cal.;forniaund_, ,MarshallSpaceFlightCenter, ,Direct:or,ResearchandDevelopment, ,beingresponsibleforSections2and4, :(1)theresultsofanalysis,test,andadvance dmanufacturingstudiesofIndependentResear chandDevelopmentprogcams,(2)aphaseBspace shuttleboosterstudyfundedbytheNASAM arshallSpaceFlightCenter,(3)anisogridtan ktestprogramfundedbytheNASAM arshallSpaceFlightCenter,and(4)theDeltap rogramisogridstructuraltestsfundedbytheN ASAG oddardSpaceFlightCenter, '.

2 ,BendingCylindersUnderTorsionalShearCyli nderUnderUniformExternalPressureln-Plane ConcentratedIx}adinInfiniteSheetIn-Plane ConcentratedLoadatEdgeofSheetCutoutReinf orcementOpenIsogridShearWebs()penIsogrid CylindersinCompression,BendingOpenandSki nnedIsogridtqatesMinimumOverallWeightfor CylinderSubjectedtoAxialCompressionandBe ndingNoteonUseofx,y;o,,(. ' ' '.001ill,? ] [m----_? (a,6)CurvesIsogridisSimpletoAnalyzeDistr ibutingConcentratedLoadEquipmentAttached toNodesSkylabFloorandWallGridReinforcedH oleforConcentratedLoadFail-SafeConceptAc cessDoorDesignsSpeedBrakesManufacturingS amplesofIsogridFormingIsogridSampleOptim umCurvesforSphericalCapwithReversePressu reDesignofIsogridSphericalBulkheadsLengt hDependenceofTheoreticalAxialCompression andBendingBucklingSolutionsInteractionCu rveShowingtheEffectofLengthWeightofOptim izedCompression-CriticalIsogridCylinders DesignofIsogridCylindersX,Y,a, ,Y,a.)

3 5 CurvesforCylindersUnderUniformExternalPr essureMasterCurvesforUniformExternalPres sureMasterCurvesforUniformExternalPressu reConcentratedLoadShearPanelk1,a,6 Curvesk2,a,5,.,-esX,Y,a,6 CurvesIsogridNodeMachiningIsogridwithUnf langedRibsMachiningIsogridwithFlangedRib sATankWallConfigurationElectricalDischar ge(EDM)orElectrochemical(ECM) , , , ! :a=[32 ISOGRIDDEFINITIONS thicknessofskinwidthofribwebdepthofwebde pthofflangewidthofflanget+d=platethickne ssofunflangedisogridheightoftrianglelego ftriangle, ,d:=mt'KDteffdistancecentertocenterofnod esTcbdwc =_'_-W'_:t-ffnon-dimensionalparameters(l +_+_I[3(I+6_z+-3_I* )z+I+_62*_ z]3[(1+6)-b_(l+k)]2bendingstiffnessparam eter.)]

4 (Forunflangedisogrid, ,_z:[3_(1+6)z+(1+_)(1+_62)].)Et2(1+a+_)1 -visogrid):extensionalstiffness(Iz=0foru nflanged=(Et312)(( )1+a+ ISOGRID ):t(I+a+_)bendingstiffness(g :0forunflanged:equivalentthicknessformem branestresses(1_=0forunflangedisogrid)t( 1+3a 3t_)=equivalentweightthickness(_:0forunf langedisogrid)vlll_LtE_=01t1+_+_Equivale ntthicknessandYoung'smodulus=toobtaincor rectKandD(_=0forunflangedE(1+a+_)Zisogri d)UseofE*andt*inmonocoqueequationsgivesc orrectstressresultants,couples,strains, ,lightweight,economical, , compression -load-carryingstructuresform partofallair-craft,booster, ,frame,anctskinconstruction,whichareofco urse9' ,however,weredesignedasint(:graliystiffe nec} ,theS-IIsecondstageduplicatedaircraft0-t o90-degreepat=ernswithanintegral, ,aswellastheThor.))

5 Reeand45-degreestiffeningpatternsu_edint hestagesoftheSaturnvehi, ,theyareinherentlyfourbarlin,< , ,Reference1-1, , , ,,' ,thisstiffeningconceptisnowbeingusedasst ructureforDeltavehicletanksandinterstage s(Reference1o2),Deltashrouds,orbitalshro uds, " ISOGRID " , ISOGRID (triangularintegralstiffening) (1)thecapabilityofcarryinghightorquesfro mthewings,(2)supplyingmultipleattachpoin tsforanexternalthermalprotectionsystem,a nd(3) (1)hightorsional_'esistance,(2)manynodal points,whichcouldbeusedasattachpointsfor thethermalprotectionsystem3tandoffstruct ures,and(3)thecapabilityofresistingtheor biterattachloadswithlocalstiffeningofthe isog_' ,Figure1-1, , ,bothbuiltinthesamestructuralstyle,mustb eattributedmainlytotheinstallationofequi pmentinnon-standardfashionintheformercom partment(seeFig ure1-2).

6 Evidently, ,muchasisogrid, "-'-----C) (CONICAL)AFTSKIRTSKINAND"; ,-USEOFTIIEtL,kNI)t_()C)t,,.Thishandhoot<pr,,suntsinforr;_,;t:o:llu't'e!_,dtodesignis,)firid,triangularintegralstiffenedstructur4, ,,'>-pointsal)()utis(,uri({ar,,.,,t_)\ ('(},.' ,.:,_.(',_tndflaF=_vrlis()_t'idwiththvin l(_rzll,,tioz'ionflangediso_ri(lh_,in,,: soct,. ,, \11()th,,riIlt'(_rzl,nli_,nnpt)li,,sl(,u nflanRediso, ,,rth,, ,s()_'.'idispr,'_,_' ,,rtin,":,_'cti(>n2,"]h 'usershouldacquaintIzill_s,,ltxxllhthi_a nalysisnnditsa, ()llSl)('i'Ol'("usinRthehandl)n()l<.B()t htlllIl;tllt2_,(']all(ll'lnn_ediso, ) (-basicth(,oryi-su,'_11_ilrix_,datth{,cn ([()tth.)))))))}

7 _,cti(_i1t_)s(,r\_,asareadyr,'f(,renc(, ,dkli(Itii_'I,_N,_iii,l,ll,,lllllllt,,I, i!l,i!,l,i_,,I|iIt_,l,ill,'lll1,0,004 Tablei-1 ISOGRID00 Alatticeofintersectingribsforminganarray ofequilateraltriangh,sCharacteristics:-I sotropic(nodirectionsofinst,,bilitvt)rwe akness)-Poisson'sratio1/-Efficientinconl p,,-cssi_nandbcndint,Advantages:-Easilya nalyzed-Canbeoptimizedforwiderang_, ,_a:'commodateequipm,,nt_nountine,witlmu tchan_t.)-Readilyreinforcedforconccntrat t,dloadsanticutouts-Redundantloadpaths-L essstructuraldt, ,,,_ccproorams,'lilot'-l)cltaandSkylal_, andcxtunsix'clyinvcsti_aludandtestedonsp aceshuttlestudyeffortSection3describt,st hechl,raclt'risticsandadvantal2,'sofisog rid,includingsomecurrentandlttlurt,appli cation:,!)

8 Orvt,hiclt, ,,Ihodsfo,"typicalstruclurufoundiraat,to -spacevehicles,l'ypicaltit,signsiluatit, nsat,,describedfor"eachtypeofstructure,a ntinwthods_foptiTr:i.<in,.:thestruclttr' t,fornainimutalw,'ightart,Rivenwheresuch mvthedsexist."lh,,nwthodofanalx'sisisfol lowedbyworkedexamples,whichart,gix',,nto ,e,,,fi(l_,tht,trs,,rinllu,applicationof theequationsandofthegraphs,"Ih,,tzraphs, ,nal)luthe,u,-,,rtoquicklyandaccuratelys izeisogridslruclur,,."l'h,,structuralIx, pusprest,nt,,darc: Sphericalcat)withr,,','(,rs(,prt,ssuru Cylindersincotlq) )_, Cylindersund_,rtorsion,_! ' , ,tethesections.

9 ,informationisgivenon:(1)theminimumovera llweightforcylinderssubjectedtoaxialcomp res,_ionandbending,and(2) , , ,.. ,amodel,sub-scale, , : Machining Powerbrakeforming Creepandageforming CompoundcurvaturesReferenctsusedintht, ' "Section2 BASICTHEORYT heisogridrib-gridsareanalyzedby"smearing out",averaging, ,thesmeared-outelasticconstantsareidenti cal' ,theco,npositeconstructionistreatedasani sotropiclayeredmaterial,withappropriatee lasticconstantsforeachlayer,viz., ,thestressesinth." , , 'SLAWFORISOGRIDRIB-GRIDT heisogridribpatternconsistsofanetworkofe quilateral(60degree) 'slawrelationsaredevelopedbyisolatingane len_entofthegridworkandassumingthatthein dividualbarsareir, /\ElementofIsogridRibCridXBymeansofthest raintransformationlaw, +YsinOcosO.

10 +eeixxxyixYx( )oneobtainatherela:ionbetweentheuniaxial barstrains,ei,andthex,yand_ gridcoordinatestrains,ex,eyxyele2'3!40I- q_( ) ,known(forexamplefromstraingagereadings} then(ex,Infact,eyt'Oi'''102q'_-2 2-1Ze3sothatif(el,e2,e3)areYxy'ey)maybe( ,_) ,2,3{ }Resolutesofthebarloadsinthexandydirecti onsdividedbytheperiodiclengths,aand_tTag ivethe"smeared-out" +(P2+P3}cos60 4Pl+P2+P3( )Ha2_a(P_+P_)sin60 _(P2+P3}ya2a( )(P2-P3)sin60 P2-P3( )--T----TXyyX'_a2aUsingeq.( ),thrsebecome,{x}yih33]{} ( )whert_h-_-a, ( )and( }withtheHooke'slawrelationforisotropicma terialsinplanestress,(ry1-v2vyxyEryx-2(l +v}Xxyitisevidentthateq.))))))