Patent Description:
To overcome this problem, repair of these propulsion structures require the structures to be removed from the aircraft and disassembled so that they can be completely enclosed in a giant vacuum bag. The number of labor hours required to disassemble and then reassemble the part adds days to the repair process, complicates the repair process, and requires specialized equipment and facilities, increasing the cost of repair and the downtime of aircraft.

<CIT>, in accordance with its abstract, states: The disclosure relates to onsite repairs of a composite structure such as an aircraft structure in which a concave recess is machined in the damaged zone, a non-polymerized composite part is set into said recess and part is polymerized under pressure using tooling comprising a stack of plates that increase the pressure applied to the composite part. The disclosure thus obtains invisible repairs with mechanical characteristics that are similar to those of the initial structure.

<CIT>, in accordance with its abstract, states: An in-situ double vacuum debulk (DVD) composite repair system designed to produce partially or fully cured autoclave quality hot-bond composite repairs on contoured structures. The system provides vacuum pressure for hot bond repairs to be performed on flat and contoured structures using one set-up capable of debulking (partially curing) and then fully curing composite repairs on composite and metallic aircraft structures. The use of in-situ DVD also eliminates handling of the patch/adhesive when transferring from an off-aircraft DVD chamber to the repair site on the aircraft. This can increase the probability of successful repairs because the possibility of contaminating and misaligning the adhesive and repair patch are eliminated.

<CIT>, in accordance with its abstract, states: A method of curing a composite layup may include applying an inner bag vacuum pressure to an inner bag chamber and an outer vacuum pressure to an outer vacuum chamber. The vacuum inner bag chamber may be formed by a vacuum bag covering a composite layup and sealed to a forming tool with an inner bag chamber seal. The inner bag vacuum pressure may be no less than the outer vacuum pressure. The temperature of the composite layup may be increased to an elevated temperature to initiate a temperature hold period. The method may additionally include venting the outer vacuum chamber to atmosphere to initiate an outer vacuum chamber venting period during the temperature hold period, and applying compaction pressure to the inner bag chamber seal during the outer vacuum chamber venting period. The outer vacuum pressure may be re-applied to the outer vacuum chamber to terminate the outer vacuum chamber venting period.

<CIT>, in accordance with its abstract, states: In order to repair a composite-material panel forming part of the external surface of an aircraft, a portable device is applied onto that surface, the portable device including an inflatable chamber consisting of a flexible and airtight membrane and a concave body of rubber-like material sealed with the membrane. The concave body incorporates an inextensible inner reinforcement. Pressurized air is introduced into the chamber via a valve. A further valve, which passes through the membrane in a zone of the membrane external to the chamber, is used to suck air from one side of the membrane to the other.

Described and defined in the appended claims are methods and systems for repair of composite components without the use of vacuum bagging. Systems described herein allow for repair of a structure, such as a vehicle structure, with a composite repair patch known as a composite repair structure. The composite repair structure can be bonded to a vehicle structure through the application of heat and positive pressure. To prevent air and volatiles from intruding during bonding of the composite repair structure to the vehicle structure, the composite repair structure includes a film sealant disposed over a repair laminate. As the film sealant prevents intrusion of air and other volatiles, the composite repair structure can be cured and bonded to the structure to be repaired without the use of a vacuum bag.

These and other examples are described further below with reference to figures.

The disclosure may best be understood by reference to the following description taken in conjunction with the accompanying drawings, which illustrate various examples.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presented concepts. The presented concepts may be practiced without some, or all, of these specific details. In other instances, well known process operations have not been described in detail to avoid unnecessarily obscuring the described concepts.

Currently, technique to repair certain composite vehicle components, such as nacelles or propulsor inlets with noise attenuation features, is to remove the components from the vehicle and strip down the components before repairing with a vacuum bag. Even minor repairs require removal of these very large and expensive parts from the vehicles and placement of these parts within vacuum bags. Furthermore, disassembly (fastener removals, separating surface sealed components, removal of rivets, and other such disassembly steps) and subsequent handling of such large unwieldy structures greatly increase the risk of incidental damage to the part. Thus, such techniques require a large number of hours and great care to perform and add complication and expense to the repair process.

An example of a vehicle with such structures is shown in <FIG> illustrates a vehicle with composite structures, in accordance with some examples. <FIG> illustrates a vehicle <NUM> that can be a fixed wing aircraft. In other examples, the systems and techniques described herein can be used to repair composites and structures of other types of vehicles such as other types of aircraft (e.g., helicopters, spacecraft, rockets, and other aircraft), automobiles, ships, submarines, and other such vehicles.

Vehicle <NUM> includes a plurality of vehicle structures <NUM>. In various examples, vehicle structures <NUM> can be different portions of vehicle <NUM>. For example, for the aircraft shown in <FIG>, vehicle structures <NUM> can be a fuselage, a wing (e.g., a fixed portion of the wing or a flap or other movable portion), an aircraft propulsor (e.g., a nacelle or inlet of the aircraft propulsor), an empennage, or another structure of the aircraft. Various examples of vehicle structures <NUM> can be made of composites such as one or more of fiberglass, carbon fiber, Kevlar®, and other such composites.

<FIG> illustrates a cross-sectional representation of a composite repair structure, in accordance with some examples. <FIG> illustrates a composite repair structure <NUM> for use in repairing (e.g., patching) composite structures such as vehicle structures <NUM> described herein. In some examples, composite repair structure <NUM> is used to repair composite vehicle structures by, for example, coupling or bonding to the composite vehicle structure. For example, bonding of composite repair structure <NUM> to such vehicle structures is accomplished through application of positive pressure and heat and without the use of vacuum bagging. Composite repair structure <NUM> includes film sealant 202A and 202B and repair laminate 206A-C.

Repair laminate 206A-C includes composite plies such as one or more of carbon fiber plies, fiberglass plies, Kevlar® plies, and other such composite plies. In certain examples, layers of repair laminate is laid on top of each other to form the core repair structure. Though the example shown in <FIG> illustrates a composite repair structure <NUM> that includes three layers of repair laminate 206A-C, other examples can include any number of layers of repair laminate.

Repair laminate 206A-C is bonded together with resin <NUM> or another type of polymer. Resin <NUM> penetrates through the fibers of repair laminate 206A-C to solidify repair laminate 206A-C. In certain examples, repair laminate 206A-C is, for example, pre-impregnated (pre-preg) composites with resin <NUM> pre-impregnated within repair laminate 206A-C. The pre-preg is heated during production to liquefy resin <NUM>, allowing resin <NUM> to penetrate the fibers of repair laminate 206A-C and displace any air within the fibers. As any air remaining within repair laminate 206A-C can weaken composite repair structure <NUM>, repair laminate 206A-C is fully penetrated with resin <NUM> to fully displace any air during the production process. Fully displacing the air maximizes the strength of composite repair structure <NUM>.

Repair structures are typically heated to bond the repair structures to vehicle structures. As repair structures are heated, resin will return to a liquid state. In conventional repair processes, containing the vehicle structure and repair structure within a vacuum bag prevents subsequent air intrusion while the resin is in the liquid state. However, without vacuum bagging, air and other volatiles will intrude into the resin and thus the repair laminate during conventional repair processes, causing porosity and weakening the structure.

Film sealant 202A and 202B is disposed on surfaces of repair laminate 206A-C. Thus, for example, film sealant 202A is disposed on a first surface of repair laminate 206A-C and film sealant 202B is disposed on a second surface of repair laminate 206A-C opposite the first surface. In various examples, film sealant is disposed on a variety of portions of repair laminate 206A-C or on all outer surfaces of repair laminate 206A-C. Film sealant (including film sealant 202A and 202B) prevents air intrusion to the repair laminate during bonding of composite repair structure <NUM> to vehicle structure <NUM>. As the film sealant prevents air intrusion to the repair laminate, composite repair structure <NUM> can accordingly be bonded to a vehicle structure without the use of vacuum or vacuum bag.

In certain examples, to prevent intrusion of air and other volatiles, film sealant 202A and 202B has a higher minimum viscosity temperature than that of resin <NUM>. Thus, film sealant 202A and 202B function as effective air barriers when the resin is most vulnerable to air intrusion (e.g., when the resin is at its lowest viscosity, such as when composite repair structure <NUM> is heated to bond composite repair structure <NUM> to vehicle structure <NUM>). During the repair process, as the temperature increases due to heating, resin <NUM> then subsequently gels (e.g., the viscosity of resin <NUM> increases) to the point where air no longer or only minimally penetrates resin <NUM> and/or repair laminate 206A-C. At this increased temperature, viscosity of film sealant 202A and 202B can then be at its minimum level. Film sealant 202A and 202B can thus comingle with resin <NUM> and any adhesives on the vehicle structure, creating a strong and durable bond.

As such, film sealant 202A and 202B, as well as any other film sealant disposed on the surface of composite repair structure <NUM>, allow for composite repair structure <NUM> to be bonded to vehicle structure <NUM> without the use of a vacuum bag while still preventing air and volatiles intrusion into resin <NUM>.

Various steps of vacuum bag-less repair techniques are now illustrated herein. <FIG> illustrates a cross-sectional representation of a step in a technique of composite repair utilizing the composite repair structure of <FIG>, in accordance with some examples. <FIG> illustrates an assembly 300A detailing a step when composite repair structure <NUM> is coupled to vehicle structure <NUM>. Assembly 300A illustrates a step where composite repair structure <NUM> is positioned on vehicle structure <NUM> (e.g., to prepare for bonding during a patch repair).

Thus, composite repair structure <NUM> is placed over portion <NUM> of vehicle structure <NUM>. In certain examples, portion <NUM> is a portion of vehicle structure <NUM> that requires repair. Film adhesive <NUM> is placed on portion <NUM>. Film adhesive <NUM> is placed between portion <NUM> and composite repair structure <NUM>. Film adhesive <NUM> encourages the bonding of composite repair structure <NUM> to portion <NUM>.

Compaction bag <NUM> can optionally be placed over and/or contain composite repair structure <NUM> to provide a vacuum to properly seat composite repair structure <NUM> over portion <NUM>. In certain examples, compaction bag <NUM> does not meet the typical vacuum requirements of a vacuum bag application. Instead, compaction bag <NUM> can be a temporary compaction bag for seating composite repair structure <NUM>. In certain examples, a release film <NUM> is disposed between composite repair structure <NUM> and compaction bag <NUM> to promote release of compaction bag <NUM> from composite repair structure <NUM> once composite repair structure <NUM> is seated. After use, compaction bag <NUM> can be discarded. Alternatively, in some examples, compaction bag <NUM> is vented to atmosphere to remove vacuum from repair laminate <NUM> and positive pressure and/or heat is applied through or over compaction bag <NUM>.

<FIG> illustrates a cross-sectional representation of another step in the technique of composite repair utilizing the composite repair structure of <FIG>, in accordance with some examples. <FIG> illustrates an assembly 300B detailing a step when composite repair structure <NUM> is bonded to vehicle structure <NUM>.

In certain examples, after composite repair structure <NUM> is coupled to vehicle structure <NUM>, release film <NUM> is disposed over composite repair structure <NUM>. A compliance layer <NUM> is then applied over release film <NUM>. In certain such examples, compliance layer is a thin (e.g., <NUM> inch or thinner), low durometer, thermally conductive material that will conform to the shape of the repair (e.g., of composite repair structure <NUM>) to provide better load transfer to composite repair structure <NUM>.

Heating blanket <NUM> is disposed over compliance layer <NUM>. Heating blanket <NUM> is configured to provide heat to composite repair structure <NUM> and/or portion <NUM> to allow composite repair structure <NUM> to bond to portion <NUM>. Additionally, in certain examples, a layer of silicone rubber foam (e.g., between <NUM> to <NUM> inches thick) is placed over heating blanket <NUM> to thermally isolate the repair from items that provide positive pressure <NUM> to the repair.

Heating blanket <NUM> provides heat to increase the temperature of composite repair structure <NUM> and/or vehicle structure <NUM>. Certain examples of heating blanket <NUM> are configured to heat composite repair structure <NUM> to a variety of different temperatures. Thus, for such examples, heating blanket <NUM> increases the temperature of composite repair structure <NUM> through a period of time by continuously providing heat to composite repair structure <NUM>. As such, composite repair structure <NUM> is heated through a period of time. For example, composite repair structure <NUM> is first heated to a first temperature whereby resin <NUM> is more viscous or liquid to aid in bonding with vehicle structure <NUM>. As the temperature increases, resin <NUM> begins to harden while film sealant 202A and 202B becomes more viscous or liquid. The decreasing viscosity of film sealant 202A and 202B allows film sealant 202A and 202B to comingle with resin <NUM> and any adhesives of vehicle structure <NUM>, creating a strong and durable bond.

In certain examples, positive pressure <NUM> is further provided to create a strong and durable bond. Positive pressure as described herein denotes any sort of pressure applied. For example, positive pressure includes pressure provided by weight (e.g., shot or sand bags), a machine (e.g., an actuator, a clamp, press, or other machine), a pneumatic bladder or through other techniques to provide pressure. In some examples, positive pressure <NUM> is any amount of pressure, including pressure of between <NUM> to <NUM> pounds per square inch (psi) applied to composite repair structure <NUM>. Positive pressure <NUM> further bonds composite repair structure <NUM> to vehicle structure <NUM> by allowing resin <NUM>, film sealant 202A and/or 202B, and/or any adhesives of vehicle structure <NUM> to comingle and/or mix to form a strong bond.

<FIG> is a process flowchart corresponding to a method of composite repair, in accordance with some examples. Various operations of method <NUM> of <FIG> are executed using systems and apparatus described herein. Steps <NUM> to <NUM> describe forming <NUM> of composite repair structure <NUM>, while steps <NUM> to <NUM> describe the repair of a vehicle structure with the composite repair structure.

In step <NUM>, repair laminate <NUM> is laid up. In certain examples, repair laminate <NUM> includes a plurality of composite plies (e.g., carbon fiber composite plies). The plies laid up in step <NUM> form repair laminate <NUM>. In step <NUM>, film sealant <NUM> is applied to the outer surfaces of repair laminate <NUM>. Film sealant <NUM> prevents air and volatile intrusion into resin <NUM> and/or repair laminate <NUM> during vacuum bag-less bonding to vehicle structure <NUM>.

In step <NUM>, composite repair structure <NUM> is disposed within a vacuum chamber and vacuum is provided to composite repair structure <NUM>. Such vacuum is be applied, for example, in a double vacuum debulk chamber (as described in <FIG>). Double vacuum debulk allows for removal of volatiles from repair laminate <NUM> without the use of an autoclave. Double vacuum debulk allows for application of heat and vacuum to composite repair structure <NUM> without subjecting composite repair structure <NUM> to vacuum compaction (e.g., from atmospheric pressure acting on a vacuum bag).

Heat is applied during one or more of steps <NUM>, <NUM>, and <NUM> in step <NUM>. Heating of film sealant <NUM>, repair laminate <NUM>, resin <NUM>, and/or another portion of composite repair structure <NUM> to various temperatures decreases resin and/or sealant viscosity and/or partially cures the resin and/or sealant to partially cure composite repair structure <NUM>. In certain examples, heat is applied during both steps <NUM> and <NUM> to, for example, allow venting or degassing of entrapped air and gases from repair laminate <NUM> as well as, potentially, curing of repair laminate <NUM> in step <NUM> and curing of film sealant <NUM> in step <NUM>, respectively. In other examples, heat is applied during step <NUM> to first decrease viscosity to allow venting of air from repair laminate <NUM> before then partially curing both repair laminate <NUM> and film sealant <NUM> simultaneously.

As such, after step <NUM>, <NUM>, <NUM>, and/or <NUM>, composite repair structure <NUM> is formed to be in a pliant intermediate state. Such an intermediate state allows for composite repair structure <NUM> to be coupled to and conform to a surface of a vehicle structure. Once coupled to the vehicle structure, heat and positive pressure is then applied to fully cure composite repair structure <NUM> into a solid state, as described herein.

Thus, after composite repair structure <NUM> has been formed, composite repair structure <NUM> is used to repair a vehicle structure in steps <NUM> to <NUM>. In step <NUM>, the surface of a portion of vehicle structure <NUM> to be repaired is prepped. Prepping includes, for example, applying film adhesive <NUM> over the surface of vehicle structure <NUM>, cleaning and sanding of the surface of vehicle structure <NUM> (e.g., to promote better adhesion), and/or other such preparation activities.

After vehicle structure <NUM> has been prepped in step <NUM>, composite repair structure <NUM> is coupled to vehicle structure <NUM> in step <NUM>, according to techniques described herein. Thus, for example, composite repair structure <NUM> is positioned over a portion of vehicle structure <NUM> to be repaired. In certain examples, compaction bag <NUM> is also be disposed over composite repair structure <NUM> to seat composite repair structure <NUM> over the proper portion of vehicle structure <NUM>.

Composite repair structure <NUM> is thus be properly positioned over vehicle structure <NUM>. Afterwards, composite repair structure <NUM> is then cured and/or bonded <NUM> to vehicle structure <NUM> or a portion therefore in steps <NUM> to <NUM>. Curing and/or bonding <NUM> includes, for example, prepping of composite repair structure <NUM> in step <NUM>. Prepping of composite repair structure <NUM> includes, for example, applying release film <NUM> and/or disposing compliance layer <NUM> over composite repair structure <NUM>.

Heat and positive pressure is then applied in steps <NUM> and <NUM>, respectively, to cure and/or bond <NUM> composite repair structure <NUM> to vehicle structure <NUM>. In certain examples, composite repair structure <NUM> and vehicle structure <NUM> is co-bonded. That is, composite repair structure <NUM> (e.g., repair laminate <NUM>) is cured while simultaneously bonded to vehicle structure <NUM> (which is a second cured laminate).

In step <NUM>, positive pressure is applied through the techniques described herein (e.g., mechanically, through weight, through force exerted on the surface of composite repair structure <NUM>, or other another technique). In step <NUM>, heat is applied to composite repair structure <NUM> and/or vehicle structure <NUM> through, for example, heat emitted by heating blanket <NUM>, emitted by heating lamps, emitted by heat guns, or from another source. Composite repair structure <NUM> is thus be bonded to vehicle structure <NUM>. The repair is then be finalized in step <NUM> by, for example, surfacing (e.g., smoothing) and finishing (e.g., painting) of the repair.

As described herein, composite repair structure <NUM> is at least partially formed in a double vacuum debulk chamber. <FIG> illustrates a cross-sectional representation of a double vacuum debulk chamber, in accordance with some examples. Double vacuum debulk allows for removal of volatiles from repair laminate <NUM>, after repair laminate <NUM> has been laid up, without the use of an autoclave by applying heat and vacuum while forming composite repair structure <NUM> without subjecting composite repair structure <NUM> to vacuum compaction.

Double vacuum debulk chamber <NUM> shown in <FIG> includes an upper bagging film <NUM>, a breather cloth <NUM>, a hardback <NUM>, vacuum probes <NUM>, a breather <NUM>, and a lower bag <NUM>. Composite repair structure <NUM> is disposed within lower bag <NUM> during forming thereof. Upper bagging film <NUM> is a vacuum bag and is configured to contain a vacuum. Vacuum probes <NUM> allow for adjustment of vacuum within upper bagging film <NUM>.

Hardback <NUM> is disposed over lower bag <NUM> and, in certain examples, is a rigid or semirigid structure. In certain examples, hardback <NUM> prevents upper bagging film <NUM> from imparting force on lower bag <NUM> when there is a vacuum within upper bagging film <NUM>. As vacuum is generated within upper bagging film <NUM>, hardback <NUM> prevents compaction force from the vacuum within upper bagging film <NUM> from being imparted onto composite repair structure <NUM> (contained within lower bag <NUM>). Thus, hardback <NUM> allows composite repair structure <NUM> to be formed within a vacuum, but without being subjected to compaction forces from the vacuum.

<FIG> illustrates a cross-sectional representation of a lower bag of the double vacuum debulk chamber of <FIG>, in accordance with some examples. <FIG> further illustrates lower bag <NUM>. Lower bag <NUM> shown in <FIG> includes a lower bagging film <NUM>, a breather <NUM>, nonporous release film <NUM> and <NUM>, a bleeder <NUM>, porous or perforated release film or fabric <NUM>, a thermally conductive sheet <NUM>, heating element <NUM>, a breather <NUM>, and electrical circuitry <NUM>. In the example shown, composite repair structure <NUM> is disposed within the layers of porous or perforated release film or fabric <NUM>.

Electrical circuitry <NUM> provides electrical power to heating element <NUM>. Heating element <NUM> is, for example, a heating blanket. Heating element <NUM> generates heat from the provided electrical power. The heat is then used to reduce the resin viscosity of the composite repair structure <NUM>. In some examples, preventing air compaction while repair laminate <NUM> is formed (e.g., when vacuum is generated and heat is provided by heating element <NUM>) allows for the extraction of gases and other volatiles from the fibers of repair laminate <NUM>. The reduced viscosity of resin <NUM> allows for resin <NUM> to flow into the volume previously occupied by the gases and volatiles. In certain examples, resin <NUM> can then occupy most or all of the space around the fibers of repair laminate <NUM>.

In certain examples, after extraction of the gases and volatiles, hardback <NUM> is vented to atmosphere. Atmospheric pressure is then able to impart a compaction force on lower bag <NUM> and, thus, composite repair structure <NUM> to form composite repair structure <NUM> to the final shape. By applying compaction forces only after the gases and volatiles are extracted, the techniques described herein allow for venting of trapping of gases and volatiles and, thus, avoid trapping of such gases and volatiles within composite repair structure <NUM>. Such a technique produces a stronger composite repair structure <NUM>. Afterwards, composite repair structure <NUM> is removed from double vacuum debulk chamber <NUM> and ready to bond to a vehicle structure.

While the systems, apparatus, and methods disclosed above have been described with reference to airplanes and the aerospace industry, it will be appreciated that the examples disclosed herein is applicable to other contexts as well, such as automotive, railroad, and other mechanical and vehicular contexts. Accordingly, examples of the disclosure is described in the context of an airplane manufacturing and service method <NUM> as shown in <FIG> and vehicle <NUM> as shown in <FIG> in applicable to such other contexts.

<FIG> illustrates a flow chart of an example of a vehicle production and service methodology, in accordance with some examples. In some examples, during pre-production, method <NUM> includes the specification and design <NUM> of vehicle <NUM> (e.g., an aircraft as shown in <FIG>) and material procurement <NUM>. During production, component and subassembly manufacturing <NUM> and system integration <NUM> of vehicle <NUM> takes place. Thereafter, vehicle <NUM> goes through certification and delivery <NUM> in order to be placed in service <NUM>. While in service by a customer, the vehicle <NUM> is scheduled for routine maintenance and service <NUM> (e.g., modification, reconfiguration, refurbishment, and so on).

In certain examples, each of the processes of method <NUM> is performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator includes any number of airplane manufacturers and majorsystem subcontractors; a third party includes any number of venders, subcontractors, and suppliers; and an operator can be an airline, leasing company, military entity, service organization, and so on.

Claim 1:
A method (<NUM>) comprising:
forming (<NUM>) a composite repair structure (<NUM>), wherein the composite repair structure (<NUM>) comprises a repair laminate (<NUM>), and wherein the forming (<NUM>) the composite repair structure (<NUM>) comprises applying (<NUM>) a film sealant (<NUM>) to a first surface (204A) of the repair laminate (<NUM>);
coupling (<NUM>) the composite repair structure (<NUM>) to a vehicle structure (<NUM>); and
curing and/or bonding (<NUM>) the composite repair structure (<NUM>) to the vehicle structure (<NUM>) by providing (<NUM>) a positive pressure (<NUM>) to the composite repair structure (<NUM>) coupled to the vehicle structure (<NUM>), wherein the film sealant (<NUM>) prevents air intrusion into the repair laminate (<NUM>) during the curing and/or bonding (<NUM>) of the composite repair structure (<NUM>) to the vehicle structure (<NUM>);
wherein the repair laminate (<NUM>) comprises a resin (<NUM>),
wherein the film sealant (<NUM>) has a higher minimum viscosity temperature than the resin (<NUM>);
wherein the sealant minimum viscosity temperature is a temperature where the resin at least partially gels; and
wherein the positive pressure (<NUM>) is provided (<NUM>) without vacuum.