7.4 LOGISTICS LOGISTICS REQUIREMENTS REQUIREMENTS
Specialized knowledge and skills are
Specialized knowledge and skills are required to perform sound required to perform sound structural composite restructural composite repairs. pairs. RepairRepair technicians must be trained in a formal program for certification since they will be expected to perform technicians must be trained in a formal program for certification since they will be expected to perform bonded repairs on diverse structures with many different types of material.
bonded repairs on diverse structures with many different types of material.
Materials – Rep
Materials – Repair materials present air materials present another logistics support another logistics support issue. issue. While most structural While most structural compo- compo-nents on an aircraft are manufactured from prepreg composite materials, support considerations may nents on an aircraft are manufactured from prepreg composite materials, support considerations may make it desirable to use different re
make it desirable to use different repair materials. pair materials. The repair materials may be prepreg or dThe repair materials may be prepreg or dry cloth with ary cloth with a laminating resin.
laminating resin. Film and foaming adhesives, wFilm and foaming adhesives, while offering excellent sthile offering excellent structural properties, require ructural properties, require coldcold storage.
storage. Laminating resins and pLaminating resins and paste adhesives present aste adhesives present a room-temperature a room-temperature storable alternative, storable alternative, butbut have reduced performance.
have reduced performance. If the damaged structure has a lightening-strike protection scheme, tIf the damaged structure has a lightening-strike protection scheme, this musthis must be restored.
be restored.
Facilities – A field or depot composite repair facility consists of a lay-up area, a part preparation area, Facilities – A field or depot composite repair facility consists of a lay-up area, a part preparation area, a part curing area, an
a part curing area, and a material storage area. d a material storage area. An environmentally-controlled lay-up area is reqAn environmentally-controlled lay-up area is required touired to prevent contamination of the
prevent contamination of the repair surface and materials. repair surface and materials. For on-aircraft repairFor on-aircraft repair, humidity and tempera-, humidity and tempera-ture control is unlikely
ture control is unlikely. . Some form of shelteSome form of shelter should then be devised r should then be devised around the repair around the repair area. area. Repair ma-Repair ma-terials should be prepared and sealed in bags in the shop, and the bags only opened immediately prior to terials should be prepared and sealed in bags in the shop, and the bags only opened immediately prior to installation.
installation.
Because a depot repair facility must perform repairs which range up to out-right component Because a depot repair facility must perform repairs which range up to out-right component remanu-facture, the facilities should replicate those of the original equipment manufacturer
facture, the facilities should replicate those of the original equipment manufacturer. . Floor space is less atFloor space is less at a premium at the depot than it would be in a field environment; thus separate lay-up, bonding, tool a premium at the depot than it would be in a field environment; thus separate lay-up, bonding, tool manu- manu-facture, part machining, and p
facture, part machining, and part and tool storage areas will be available. art and tool storage areas will be available. During remanufacture, compo-During remanufacture,
compo-Volume
Volume 6, Chapter 6, Chapter 7 7 SupportabilitySupportability nents are off-aircra
nents are off-aircraft and mobile. ft and mobile. Therefore, large industrial cold-storage, curing, machiningTherefore, large industrial cold-storage, curing, machining, and inspec-, and inspec-tion equipment can be used
tion equipment can be used to perform repair operations at the depot.to perform repair operations at the depot.
Technical Data – Technical data in various forms is required to support composite repair to aircraft Technical Data – Technical data in various forms is required to support composite repair to aircraft structure.
structure. TTechnical data ranges from structural repair manuals/military technical manuals, to part draw-echnical data ranges from structural repair manuals/military technical manuals, to part draw-ings and CAD data, to loads books and finite element models for engineers.
ings and CAD data, to loads books and finite element models for engineers.
Equipment – Heat blankets, hot bonders, heat lamps, heat guns and convection ovens are portable Equipment – Heat blankets, hot bonders, heat lamps, heat guns and convection ovens are portable heating and curing equipment usually found in both the d
heating and curing equipment usually found in both the depot and field environments. epot and field environments. These are usuallyThese are usually used in conjunction with a vacuum bag, to expedite moisture removal prior to repair, and to provide used in conjunction with a vacuum bag, to expedite moisture removal prior to repair, and to provide con-solidation pressure to the repair
solidation pressure to the repair. . They can be used to manufacture pre-cured composite repThey can be used to manufacture pre-cured composite repair patchesair patches and to bond repairs to the componen
and to bond repairs to the component. t. Whatever the portable heat source, Whatever the portable heat source, generous use of thermocou-generous use of thermocou-ples must be made to
ples must be made to closely monitor cure temperaclosely monitor cure temperatures. tures. Heat blankets consist of hHeat blankets consist of heating elementseating elements sandwiched between temperatu
sandwiched between temperature-tolerant flexible materials. re-tolerant flexible materials. Hot bonders are Hot bonders are programmable heat anprogrammable heat andd vacuum control units, which provide power to heat blankets automatically to an operator-specified cure vacuum control units, which provide power to heat blankets automatically to an operator-specified cure cycle.
cycle. Hot bonders Hot bonders often have often have a vacuum pump a vacuum pump included. included. Infrared heat Infrared heat lamps and lamps and heat guns arheat guns are alsoe also used for elevated temperature cures of
used for elevated temperature cures of composite repairs. composite repairs. Industrial ovens are a necessity at depotIndustrial ovens are a necessity at depots as as as a means of drying and curing composite parts and repairs.
means of drying and curing composite parts and repairs. Autoclaves are pressurized ovens usually foundAutoclaves are pressurized ovens usually found at depot facilities for part repair and remanu
at depot facilities for part repair and remanufacture. facture. The typical 85 psi (586 kPa) pressures required toThe typical 85 psi (586 kPa) pressures required to achieve maximum consolidation of a composite prepreg lam
achieve maximum consolidation of a composite prepreg laminate make large structural repairs possible.inate make large structural repairs possible.
Cold storage e
Cold storage equipment that can quipment that can maintain material at maintain material at 0°0°F (-18°F (-18°C) or C) or lower is lower is required to required to maintainmaintain shelf-life on most prei
shelf-life on most preimpregnated materials and ampregnated materials and adhesives. dhesives. For paint removal and For paint removal and machining of curedmachining of cured composite materials, down or side draft facilities separate from the bonding and curing area are required composite materials, down or side draft facilities separate from the bonding and curing area are required to remove dust
to remove dust produced during machining operatproduced during machining operations. ions. Both field and depot Both field and depot facilities require equipmentfacilities require equipment for nondestructive inspection
for nondestructive inspection of composite components. of composite components. Radiography (X-ray), Radiography (X-ray), thermography (infra-red),thermography (infra-red), ultrasonic and laser shearography inspection equipm
ultrasonic and laser shearography inspection equipment may be required for pre-repair damage mapping,ent may be required for pre-repair damage mapping, in progress inspection, and post-repair inspection.
in progress inspection, and post-repair inspection.
Volume
Volume 6, Chapter 6, Chapter 7 7 SupportabilitySupportability
REFERENCES REFERENCES 7.2.7
7.2.7 Flynn, Flynn, B., B., et. et. al., al., “Advanced “Advanced TTechnology echnology Composite Composite Fuselage Fuselage - - Repair Repair and and Damage Damage As- As-sessment Supporting Maintenance”, NASA CR-4733, 1997.
sessment Supporting Maintenance”, NASA CR-4733, 1997.
7.3.1
7.3.1 “Composite “Composite Repair Repair NDI NDI and and NDT NDT Handbook” Handbook” ARP ARP 5089, 5089, SAE, SAE, 19961996 7.3.4.2(a)
7.3.4.2(a) “General “General Advanced Advanced Composite Composite Repair Repair Manual”, Manual”, TTechnical echnical Manual, Manual, TO TO 1-1-690, 1-1-690, U.S. U.S. AirAir Force, July 1984
Force, July 1984 7.3.4.2(b)
7.3.4.2(b) “General Composite “General Composite Repair”, Repair”, Organizational Organizational and and Intermediate Intermediate Maintenance, Maintenance, TTechnicalechnical Manual, NAV
Manual, NAVAIR 01-1A-21, AIR 01-1A-21, January 1994January 1994 7.3.4.3(a)
7.3.4.3(a) Francis, C.FFrancis, C.F., ., Rosenzweig, Rosenzweig, E., E., Dobyns, Dobyns, A., A., Brasie, Brasie, S., S., “Development “Development of of Repair Repair Methodol- Methodol-ogy for the MH-53E
ogy for the MH-53E Composite Sponson,” in 1997 USAComposite Sponson,” in 1997 USAF Aircraft StF Aircraft Structural Integrity Pro-ructural Integrity Pro-gram Conference, San Antonio, TX, 2-4
gram Conference, San Antonio, TX, 2-4 December 1997.December 1997.
7.3.4.3(b)
7.3.4.3(b) Dodd, Dodd, S., S., PetterPetter, , H., H., Smith, Smith, H., H., “Optimum “Optimum Repair Repair Design Design for for Battle Battle Damage Damage Repair, Repair, VolumeVolume II: Software User’s Manual,” W
II: Software User’s Manual,” W L-TR-91-3100, McDonnell Douglas Corp., L-TR-91-3100, McDonnell Douglas Corp., FebruaryFebruary, 1992., 1992.
7.3.4.3(c)
7.3.4.3(c) Hart Hart Smith, Smith, J., J., ”Adhesive-Bonded ”Adhesive-Bonded Scarf Scarf and and Stepped-Lap Stepped-Lap Joints,” Joints,” NASA NASA CR CR 1112237,12237, Douglas Aircraft Co., Ja
Douglas Aircraft Co., Januarynuary, 1973., 1973.
7.3.4.3(d)
7.3.4.3(d) “Elastic Adhesive “Elastic Adhesive Stresses Stresses in in Multistep Multistep Lap Lap Joints Joints loaded loaded in in TTension,” ension,” ESDU ESDU 80039,80039, Amendment B, Engineering Sciences Data Unit International plc,
Amendment B, Engineering Sciences Data Unit International plc, London, NovemberLondon, November 1995.”
1995.”
7.3.4.4
7.3.4.4 “Core “Core Restoration Restoration of of Thermosetting Thermosetting Composite Composite Materials”, Materials”, ARP ARP 4991, 4991, SAE, SAE, 19961996
CONCLUDING MATERIAL CONCLUDING MATERIAL
Custodians:
Custodians: Preparing Preparing activity:activity:
Army
Army - - MR MR Army Army - - MRMR
Navy - AS Navy - AS Air
Air Force Force - - 11 11 (Project (Project CMPS-0172)CMPS-0172) Review activities:
Review activities:
Army - AR, AT, AV, MI Army - AR, AT, AV, MI Navy - SH
Navy - SH Air Force - 13 Air Force - 13 DLA-IS
DLA-IS