ASTM_E_2981_-_15.pdf

Designation:E298115Standard Guide forNondestructive Testing of the Composite Overwraps inFilament Wound Pressure Vessels Used in AerospaceApplications1This standard is issued under the fixed designation E2981;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide discusses current and potential nondestruc-tive testing(NDT)procedures for finding indications of dis-continuities and accumulated damage in the composite over-wrap of filament wound pressure vessels,also known ascomposite overwrapped pressure vessels(COPVs).In general,these vessels have metallic liner thicknesses less than 2.3 mm(0.090 in.),and fiber loadings in the composite overwrapgreater than 60 percent by weight.In COPVs,the compositeoverwrap thickness will be of the order of 2.0 mm(0.080 in.)for smaller vessels and up to 20 mm(0.80 in.)for larger ones.1.2 This guide focuses on COPVs with nonload-sharingmetallic liners used at ambient temperature,which mostclosely represents a Compressed Gas Association(CGA)TypeIII metal-lined composite tank.However,it also has relevanceto 1)monolithic metallic pressure vessels(PVs)(CGAType I),2)metal-lined hoop-wrapped COPVs(CGA Type II),3)plastic-lined composite pressure vessels(CPVs)with anonload-sharing liner(CGAType IV),and 4)an all-composite,linerless COPV(undefined Type).This guide also has rel-evance to COPVs used at cryogenic temperatures.1.3 The vessels covered by this guide are used in aerospaceapplications;therefore,the inspection requirements for discon-tinuities and inspection points will in general be different andmore stringent than for vessels used in non aerospace applica-tions.1.4 This guide applies to 1)low pressure COPVs used forstoring aerospace media at maximum allowable working pres-sures(MAWPs)up to 3.5 MPa(500 psia)and volumes up to 2m3(70 ft3),and 2)high pressure COPVs used for storingcompressed gases at MAWPs up to 70 MPa(10,000 psia)andvolumes down to 8000 cm3(500 in.3).Internal vacuum storageor exposure is not considered appropriate for any vessel size.1.5 The composite overwraps under consideration includebut are not limited to ones made from various polymer matrixresins(for example,epoxies,cyanate esters,polyurethanes,phenolic resins,polyimides(including bismaleimides),andpolyamides)with continuous fiber reinforcement(for example,carbon,aramid,glass,or poly-(phenylenebenzobisoxazole)(PBO).The metallic liners under consideration include but arenot limited to aluminum alloys,titanium alloys,nickel-chromium alloys,and stainless steels.1.6 This guide describes the application of established NDTmethods;namely,Acoustic Emission(AE,Section 7),EddyCurrent Testing(ECT,Section 8),Laser Shearography(Section9),Radiologic Testing(RT,Section 10),Thermographic Test-ing(TT,Section 11),Ultrasonic Testing(UT,Section 12),andVisual Testing(VT,Section 13).These methods can be used bycognizant engineering organizations for detecting and evaluat-ing flaws,defects,and accumulated damage in the compositeoverwrap of new and in-service COPVs.NOTE1Although visual testing is discussed and required by currentrange standards,emphasis is placed on complementary NDT proceduresthat are sensitive to detecting flaws,defects,and damage that leave novisible indication on the COPV surface.NOTE2In aerospace applications,a high priority is placed on lightweight material,while in commercial applications;weight is typicallysacrificed to obtain increased robustness.Accordingly,the need to detectdamage below the visual damage threshold is more important in aerospacevessels.NOTE3Currently no determination of residual strength can be madeby any NDT method.1.7 All methods discussed in this guide(AE,ET,shearography,RT,TT,UT,and VT)are performed on thecomposite overwrap after overwrapping and structural cure.For NDT procedures for detecting discontinuities in thin-walled metallic liners in filament wound pressure vessels,or inthe bare metallic liner before overwrapping;namely,AE,ET,laser profilometry,leak testing(LT),penetrant testing(PT),andRT;consult Guide E2982.1.8 In the case of COPVs which are impact damage sensi-tive and require implementation of a damage control plan,emphasis is placed on NDT methods that are sensitive to1This test method is under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.10 onSpecialized NDT Methods.Current edition approved July 1,2015.Published September 2015.DOI:10.1520/E2891-15.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 detecting damage in the composite overwrap caused by im-pacts at energy levels and which may or may not leave anyvisible indication on the COPV composite surface.1.9 This guide does not sp