dorworth presentation

8/10/2019 Dorworth Presentation

1/48

Abaris Training, 2007Abaris Training, 2007

Essentials of AdvancedEssentials of AdvancedComposite Repair Composite Repair

Louis C. DorworthLouis C. Dorworth Abaris Training Resources, Inc. Abaris Training Resources, Inc.

www.abaris.comwww.abaris.com


2/48


Why Repairs Are NecessaryWhy Repairs Are Necessary

on Aircrafton Aircraft


3/48


737737 -- 800 is 4 feet taller than older 737800 is 4 feet taller than older 737 -- 400 model400 model

41 foot high tail Vs. 38 foot tall41 foot high tail Vs. 38 foot tallhanger door openinghanger door opening


4/48


5/48


Repairs are necessary inRepairs are necessary in

motosports as wellmotosports as well


6/48


Formula 1 RacingFormula 1 Racing


7/48


Rally Car RacingRally Car Racing


8/48


Motorcycle RacingMotorcycle Racing


9/48


SpeedSpeed --Boat RacingBoat Racing


10/48


Tug RacingTug Racing


11/48


Boats, Planes, Trains, etc,Boats, Planes, Trains, etc,etcRepairs are Required foretcRepairs are Required forMany Composite Structures.Many Composite Structures.


12/48


Goal of Composite Repair DesignGoal of Composite Repair DesignRebuild Fiber Load Path Through StructureRebuild Fiber Load Path Through Structure

Ideal to Match Original Properties:Ideal to Match Original Properties:StrengthStrengthStiffnessStiffness

WeightWeightTradeTrade --offs:offs:

To match strength, repair is stiffer & heavier To match strength, repair is stiffer & heavier

To match stiffness, repair is weaker & heavier To match stiffness, repair is weaker & heavier Cannot match all original propertiesCannot match all original properties


13/48


Common Repair MethodsCommon Repair MethodsStepped CoStepped Co --bonded Repairsbonded Repairs

Wet layup and prepreg materials & processesWet layup and prepreg materials & processesTaperedTapered --Scarf CoScarf Co --bonded Repairsbonded Repairs

Wet layup and prepreg materials & processesWet layup and prepreg materials & processes

Bolted Doubler RepairsBolted Doubler RepairsPrePre --cured composite doublerscured composite doublers

Stainless steel or Titanium doublersStainless steel or Titanium doublers


14/48


Stepped Removal & Repair Stepped Removal & Repair Idea comes from metal lapIdea comes from metal lap -- joint repair joint repairdesign concepts.design concepts.Each damaged layer is removed in stepsEach damaged layer is removed in steps

so as to provide a landing for eachso as to provide a landing for eachreplacement layer in the repair.replacement layer in the repair.Each repair ply then overlaps theEach repair ply then overlaps the

corresponding exposed layer in thecorresponding exposed layer in thestructure.structure.


15/48


Typical Stepped Repair Typical Stepped Repair Loads are distributed through

the repair via a lap joint intothe underlying layers

The resulting repair sits above the surface

Filler Ply


16/48


Typical Stepped Repair Typical Stepped Repair

Filler Ply

Shear stress distribution in a stepped repair

Note peak stress concentrations at edges of each step withinthe repair


17/48


Typical Stepped Removal ProcessTypical Stepped Removal Process

Plies were removed in steps

using a knife to cut througheach ply and then scrape offthe ply to the correct level


18/48


Stepped RepairsStepped RepairsProsPros ::Easy to conceptualize & design.Easy to conceptualize & design.

(It looks good on paper!)(It looks good on paper!)

Feasible for flat panel repairs made withFeasible for flat panel repairs made withdiscernable materials.discernable materials.CoCo --bonded layers makes for intimatebonded layers makes for intimaterepair contact at faying surfaces.repair contact at faying surfaces.??????


19/48


Stepped RepairsStepped RepairsConsCons ::Requires meticulous machining of eachRequires meticulous machining of eachlayer in the damaged laminate so as not tolayer in the damaged laminate so as not to

damage the underlying plies. (This takesdamage the underlying plies. (This takesexceptional skill!)exceptional skill!)

Difficult to do on curved surfaces.Difficult to do on curved surfaces.

Damage to underlying layers is common andDamage to underlying layers is common andoften overlooked in the industry.often overlooked in the industry.


20/48


Stepped RepairsStepped RepairsConsCons ::Requires careful fabrication andRequires careful fabrication andplacement of repair plies so that they fitplacement of repair plies so that they fit

into each step w/o gaps or overlaps.into each step w/o gaps or overlaps.

Requires precise templates or tracings toRequires precise templates or tracings toensure repair ensure repair --ply fit.ply fit.

Unwanted gaps and overlaps often result inUnwanted gaps and overlaps often result indefects in the final repair.defects in the final repair.


21/48


Stepped RepairsStepped RepairsConsCons ::Takes a trained technician approximatelyTakes a trained technician approximately2 x the time to perform a stepped repair2 x the time to perform a stepped repaircompared to a taperedcompared to a tapered --scarf repair.scarf repair.

Airlines are not likely to do step repairs as a Airlines are not likely to do step repairs as aresult of the extra labor involved.result of the extra labor involved.


22/48


TaperedTapered --Scarf RepairsScarf Repairs A tapered A tapered --scarf angle is machined throughscarf angle is machined throughthe composite structure so as to exposethe composite structure so as to exposeeach layer along a gentlyeach layer along a gently --angled slope.angled slope.Each repair ply then lays over theEach repair ply then lays over thecorresponding exposed layer along thecorresponding exposed layer along thetapered angle.tapered angle.


23/48


Typical Repair ApproachTypical Repair Approach

Determine plies/orientations in theoriginal structure & develop repair

Replace plies/orientations tomatch the original structure

First remove damaged material and prepare area for repair


24/48


Example of a TaperedExample of a Tapered --ScarfScarfRemoval ProcessRemoval Process

Practicing a tapered scarf on an Aramidfiber reinforced epoxy sandwich structure


25/48


You Can Clearly See the Layers in ThisYou Can Clearly See the Layers in ThisTapered CFRP Sandwich PanelTapered CFRP Sandwich Panel


26/48


Typical TaperedTypical Tapered --Scarf Repair Scarf Repair Loads are transferred directly through the

edges of the repair plies, in plane, onaxis, in shear, to the underlying structure

The resulting repair is flush with the surface


27/48


Typical TaperedTypical Tapered --Scarf Repair Scarf Repair Uniform shear stress distribution

through a tapered scarf joint


28/48


Big Ply Down Scarf Repair Big Ply Down Scarf Repair Loads are transferred directly through the

big ply laid down first, fully loading thisply in the axis of its orientation prior totransferring load to adjacent plies

Abaris Training does not recommend this Abaris Training does not recommend thisrepair technique for highly loaded orrepair technique for highly loaded oroptimized composite structures! optimized composite structures!


29/48


TaperedTapered --Scarf RepairsScarf RepairsProsPros ::

Fast & easy to machine taper Fast & easy to machine taper --angle and toangle and tofabricate repair plies.fabricate repair plies.

Perfect size and fit of repair plies is lessPerfect size and fit of repair plies is lessimportant to performance.important to performance.Flush surface is attainable.Flush surface is attainable.

Important for critical aerodynamic surfaces &Important for critical aerodynamic surfaces &L.O. structuresL.O. structures


30/48


TaperedTapered --Scarf RepairsScarf RepairsProsPros ::

Can machine a taper with a die grinder orCan machine a taper with a die grinder orjitter jitter --bug sander.bug sander.

No special tools or devices necessary.No special tools or devices necessary.

Less risk of damaging underlying layers inLess risk of damaging underlying layers intapered area.tapered area.

CoCo --bonded layers makes for intimatebonded layers makes for intimaterepair contact at faying surfaces.repair contact at faying surfaces.


31/48


TaperedTapered --Scarf RepairsScarf RepairsConsCons ::

Not applicable to repairs of thick structuresNot applicable to repairs of thick structuresas one might do more damage to theas one might do more damage to theoriginal structure attaining the correct scarforiginal structure attaining the correct scarfangle ratioangle ratioMinor risk of damaging good structureMinor risk of damaging good structure

within and outside the scarf areawithin and outside the scarf area??????


32/48


Typical Wet Layup Repair ProcessTypical Wet Layup Repair Process

Remove damagedskin & core then

taper-scarfed skin

Repair/fill core cavity asrequired & machine flush


33/48


Typical Wet Layup Repair ProcessTypical Wet Layup Repair ProcessApply wet resin to dry

fabric, cover withplastic, and squeegeethe resin throughoutthe layer as needed


34/48



Wet-out the surface with an interface coat ofresin and layup each repair ply to match the

orientation of corresponding plies in structure


35/48



Apply peel ply, bleeder, & breather materials and vacuum bag for cure


36/48



After curing, remove breather, bleeder, & peel ply and inspect the repair


37/48


Prepreg Repairs Follow a SimilarPrepreg Repairs Follow a SimilarProcess and Typically Require anProcess and Typically Require anElevated Temperature Cure UsingElevated Temperature Cure Using

Portable HotPortable Hot --Bond equipmentBond equipment


38/48


Bolted Doubler RepairsBolted Doubler RepairsHistorically the norm for metal structuralHistorically the norm for metal structural

repairsrepairs Also bonded metal doublers for thin skin Also bonded metal doublers for thin skinmetal structural repairsmetal structural repairs

Normally reserved for thicker, solidNormally reserved for thicker, solidcomposite laminate structures where acomposite laminate structures where a

scarf or step repair would not be feasible.scarf or step repair would not be feasible.


39/48


DamageRemoved

Typical Doubler SectionTypical Doubler Section

Inside Doubler

Outside Doubler

Laminate Structure

Fasten as prescribed

Plug

Seal all aroundthe patch


40/48


Bolted Doubler RepairsBolted Doubler RepairsDetermining when to useDetermining when to usea doubler can be tricky.a doubler can be tricky.If the laminate is lessIf the laminate is lessthanthan inch thick:inch thick:taperedtapered --scarf repair scarf repair

If the laminate is greaterIf the laminate is greaterthan inch thick: doublerthan inch thick: doublerrepair repair

In between: do a repairIn between: do a repairdesign analysisdesign analysis


41/48


Bolted Doubler on CFRBMI PanelBolted Doubler on CFRBMI Panel


42/48


Tapered Scarf Repair onTapered Scarf Repair onSimilar CFRBMI PanelSimilar CFRBMI Panel


43/48


Bolted Doubler RepairsBolted Doubler RepairsProsPros ::

Can be faster and easier to accomplishCan be faster and easier to accomplishcompared to taper compared to taper --scarfed or stepped coscarfed or stepped co --bonded repairs.bonded repairs.

Requires less removal of original structureRequires less removal of original structure(compared to step or tapered(compared to step or tapered --scarf repairs) toscarf repairs) toaccommodate the repair.accommodate the repair.

Most mechanics are already trained in drilling &Most mechanics are already trained in drilling &fastener installation procedures.fastener installation procedures.


44/48


Bolted Doubler RepairsBolted Doubler RepairsConsCons ::

Doublers must be made to closely matchDoublers must be made to closely matchsurface contour.surface contour.

Can be problematic in compound areasCan be problematic in compound areas

Additional tooling may be required to Additional tooling may be required tofacilitate fabrication of repair patch.facilitate fabrication of repair patch.

Autoclave cure of composite patch may be Autoclave cure of composite patch may berequired to achieve properties.required to achieve properties.


45/48


Bolted Doubler RepairsBolted Doubler RepairsConsCons ::

Risks associated with drilling intoRisks associated with drilling intounderlying structure for fasteners.underlying structure for fasteners.

Expensive Ti fasteners required in carbonExpensive Ti fasteners required in carbonreinforced structures.reinforced structures.Sealing of the repair questionable and notSealing of the repair questionable and not

often durable.often durable.


46/48


SummarySummaryThe goal is to replace the structure toThe goal is to replace the structure to

serviceable strength and stiffness.serviceable strength and stiffness.It takes special training and practice to doIt takes special training and practice to dotop quality composite repairs.top quality composite repairs.

One approach does not fit all types ofOne approach does not fit all types ofdamage.damage.Repair technicians have to know theirRepair technicians have to know theirmaterials and processes in order tomaterials and processes in order toaccomplish good quality repairsaccomplish good quality repairs


47/48


Next Event Reminder!Next Event Reminder!Please plan to attend the next SME TechPlease plan to attend the next SME Tech --Group Webinair event on Tuesday, June 12Group Webinair event on Tuesday, June 12 thth ,,

2007 at 1:002007 at 1:00 --2:00 pm EDT!2:00 pm EDT!

RichRich EmrichEmrich fromfrom IntegranIntegran Technologies will beTechnologies will bepresenting a novel and innovative new tooling conceptpresenting a novel and innovative new tooling concept

involving the use of Nanovar involving the use of Nanovar surface technologysurface technologydesigned to improve the durability of advanceddesigned to improve the durability of advanced

composite molds and fixtures used in manufacturing.composite molds and fixtures used in manufacturing.This event promises to be a real learning experience!This event promises to be a real learning experience!

Contact Victoria Townsend at [email protected] more information about this exiting event!


48/48


Thank You For Attending!Thank You For Attending!Feel free to contact me directly if you haveFeel free to contact me directly if you have

additional questions after this session.additional questions after this session.

Louis C. DorworthLouis C. DorworthTechnical Director Technical Director

Abaris Training Resources, Inc. Abaris Training Resources, Inc.5401 Longley Lane, Suite 495401 Longley Lane, Suite 49

Reno, NV 89511Reno, NV 89511

[email protected]@abaris.com775775 --827827 --6598 x2286598 x228

dorworth presentation

Documents