Reinforcement members for aircraft propulsion system components configured to address delamination of the inner fixed structure

An inner fixed structure of a thrust reverser includes an inner skin, an outer skin, a cellular core disposed between the inner skin and the outer skin, and at least one crack and delamination stopper extending radially between the inner skin and the outer skin.

BACKGROUND

When a “blade-out” event occurs in an aircraft engine, it is critical that the aircraft have “fly-home” capability (i.e., the ability to return safely to the ground under FAA rules). Similarly, when one layer of a multilayer component of an aircraft propulsion system becomes disbonded from another layer, it is again critical that the aircraft be able to fly home. The ability of an aircraft propulsion system component, such as a nacelle or the inner fixed structure of a thrust reverser, to tolerate damage and maintain structural integrity during a blade-out event, disbonding of layers, or other failure mode, is critical to the fly-home capability of an aircraft.

SUMMARY

The disclosure concerns protective structures for aircraft propulsion system components, which are designed to limit cracking, disbond, and delamination, thereby improving the fly-home capability of an aircraft.

According to certain embodiments, the component is an acoustic inner barrel. The inner acoustic barrel may include: an annular inner skin; an annular outer skin; an annular acoustic cellular core assembly disposed between the inner skin and the outer skin; and at least two reinforcement members extending radially from the inner skin, through the acoustic cellular core, and to the outer skin. The inner skin, outer skin, acoustic cellular core assembly and the at least two or more reinforcement members may be bonded together to form a 360-degree, one-piece annular structure and still maintain acoustic smoothness requirements of the barrel.

According to certain other embodiments, the component is an inner fixed structure (IFS) of a thrust reverser. The IFS includes an inner skin, an outer skin, an acoustic cellular core assembly disposed between the inner skin and the outer skin, and a reinforcement lattice comprising a plurality of reinforcement members extending in a thickness direction through the cellular core between the inner skin and the outer skin. Each of the reinforcement members also extends in lateral direction of the cellular core, lateral directions associated with a first set of reinforcement members intersecting lateral directions associated with a second set of reinforcement members to thereby form the reinforcement lattice.

In some embodiments, the IFS may have a “clamshell” configuration comprising two complementary halves.

In some embodiments, the reinforcement lattice may be found only along an enlarged barrel portion of the IFS.

The reinforcement members may take on different cross-sectional shapes, such as a T-shaped cross-section, an I-shaped cross-section, an L-shaped cross-section, a Z-shaped cross section, a C-shaped cross section, in a lateral direction of the cellular core.

The reinforcement member may have a first end segment secured between an acoustic cellular core and an innermost surface of the inner skin, and a central segment adhesively boned to the core.

The reinforcement members may be bonded only to an imperforate inner skin and not bonded to a perforated outer skin.

Additional features and advantages of the invention are provided in the following detailed description and appended drawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a portion of an aircraft engine nacelle1including an acoustic inner barrel10at its inlet la, according to one embodiment of the invention. As shown inFIGS. 1 and 2, the barrel10has a 360-degree, one-piece annular construction. The barrel10includes an annular, perforated inner face sheet or inner skin12, an annular, imperforate outer face sheet or outer skin14radially spaced from the inner skin12, and an acoustic cellular core16disposed between the inner skin12and the outer skin14. The term “annular” includes constructions having varying diameters and shapes along the length L (FIG. 1) of the nacelle1, and is not intended to be limited to right cylinders. The inner skin12, outer skin14and cellular core16may be constructed of a composite material, such as graphite-epoxy, or the like. The inner skin12and outer skin14are bonded to the core16by an adhesive such as Henkel Epoxy Adhesive EA 9258.1, or another adhesive material having comparable peel and shear strengths, so as to have a 360-degree, one-piece construction. The core16may have a single-degree-of-freedom arrangement, a double-degree-of-freedom or a different multiple-degree-of-freedom arrangement of a type known to persons of ordinary skill in the art.

As shown inFIGS. 1 and 2, the barrel10includes two crack and delamination stoppers, or reinforcement members50disposed approximately 180 degrees apart around the circumference of the barrel10. The reinforcement members50extend radially from the inner skin12, through the core16and to the outer skin14. The reinforcement members50reinforce the skins12,14and the core16, and serve to limit delamination and cracking of the barrel10during accidents, such as a blade-out events, that may otherwise inflict structural damage on the nacelle1. The reinforcement members50may be made of a suitably strong, lightweight material. A composite material, such as graphite-epoxy, is preferable, although metallic materials, such as aluminum or titanium, may also be used. Although two reinforcement members50are shown, any number and spacing of reinforcement members may be used, depending on structural needs. Where multiple reinforcement members50are employed, it is preferable that the reinforcement members50be uniformly spaced around the circumference of the barrel10. For example, three reinforcement members50may be provided at approximately 120-degree spacing around the circumference of the barrel10, or four reinforcement members50may be provided at approximately 90-degree spacing around the circumference of the barrel10. It is also possible to place the reinforcement members50at non-uniform spacings around the barrel10, to accommodate non-uniform structural requirements of the barrel10.

Referring toFIGS. 3A and 3B, each reinforcement member50has an essentially Z-shaped cross-section in the axial direction (into the page) of the barrel10, and includes a central segment52extending in a first direction D1, a first end segment54extending from a first end of the central segment52in a second direction D2transversely (preferably, perpendicularly) to the first direction D1, and a second end segment56extending from a second end of the central segment52in a third direction D3opposite the second direction D2. Each reinforcement member50is preferably constructed from two or more similarly shaped plies60,70that are bonded together such that each channel member essentially forms a half of the reinforcement member50. According to a preferred embodiment, the reinforcement member50is provided as a pre-cured composite body, wherein the plies60,70are constructed of a composite material such as graphite-epoxy and bonded together by an adhesive such as 3M Scotch-Weld® Epoxy Adhesive EC-2216 B/A, or another adhesive material having comparable peel and shear strengths.

As illustrated inFIG. 3A, the ply60may extend beyond the ply70in the direction D2at the first end segment54in order to promote more secure attachment of the reinforcement member50to the inner skin12the barrel10, as will be described in more detail later. After installation in the barrel10, the first end segment54is perforated (FIG. 4) so as not to adversely impact the acoustic performance of the barrel10.

The reinforcement members50may generally have a thickness T (in the direction perpendicular to the length of a respective portion52/54/56) of about 0.030-0.050 inches (0.076-0.127 cm). According to an exemplary embodiment, each ply60,70is about 0.0075 inches (0.019 cm) thick. However, the thickness of the reinforcement members50may vary as required in a given application. Furthermore, according to an exemplary embodiment, the axial length of the reinforcement members50(in the direction L shown inFIG. 1) is approximately equal to the axial length of the core16.

Although the reinforcement members50are shown and described as formed from two bonded plies60,70, such a construction is not required. The reinforcement members may be formed from a greater number of plies, the plies may be joined by means other than bonding, or the reinforcement members may have unitary one-piece construction.

FIG. 4illustrates in detail the construction of the barrel10. As shown inFIG. 4, the central segment52of the channel member50extends radially in the direction R through the core16of the barrel10, the first end segment54of the reinforcement member50extends substantially parallel to the inner skin12in a first direction X1and the second end segment56of the reinforcement member50extends substantially parallel to the outer skin14in a second direction X2. The first end segment54is positioned between layers12a,12bof the inner skin12. The second end segment56is positioned between the radially outermost surface16aof the core16and the radially innermost surface14aof the outer skin14.

The reinforcement member50is bonded to opposing surfaces of the barrel10. Specifically, the central segment52is bonded to circumferentially opposing surfaces of the core16, the first end segment54is bonded to the surrounding layers12a,12bof the inner skin12, and the second end segment56is bonded to the radially opposing outer skin14and the outermost surface of the core16. Because the ply60is longer than the ply70in the direction D2at the first end segment54, the surface area of the first end segment54is increased, thereby providing a larger bonding surface area between the first end segment54and the inner skin12. The reinforcement member50may be bonded to the adjacent surfaces of the barrel10by an adhesive such as 3M Scotch-Weld® Epoxy Adhesive EC-2216 B/A, or another adhesive material having comparable peel and shear strengths.

It is noted that, in the embodiment shown inFIG. 4, the second end segment56is not positioned between opposing individual layers (not shown) of the outer skin14, so that the bond between the first end segment54and the inner skin12is stronger than the bond between the second end segment56and the outer skin14. Although it is possible for the second end segment56to be positioned between individual layers (not shown) of the outer skin14, such a configuration is less desirable than the configuration shown inFIG. 4. It is desirable that the bonds between the reinforcement members50and the inner skin12be stronger than the bonds between the reinforcement members50and the outer skin14, because such an arrangement provides optimum failure resistance characteristics. In a blade-out event, the engine fan blade will first strike the inner skin12, so the inner skin12will be the first part of the barrel to take damage. When the bonds between the reinforcement members50and the inner skin12are stronger than the bonds between the reinforcement members50and the outer skin14, the flow of energy from a blade-out event will follow a path extending from the inner skin12through a reinforcement member50, and then into the outer skin14. Thus, less of the energy from a blade-out event is likely to flow through a path extending around the circumference barrel10. As a result, damage from a blade-out event is more likely to be circumferentially localized at areas of impact, and is less likely to propagate circumferentially through the barrel10, thereby increasing the likelihood of a greater portion of the barrel remaining intact.

As shown inFIG. 4, and as well known in the art, the inner skin12includes perforations18that extend through the skin12to provide a desired flow of sound waves into the core16. According to an embodiment, the first end segment54of the reinforcement member50preferably includes perforations58that are substantially radially aligned with the perforations18so as to not detrimentally affect the flow of sound waves through the perforations18into the core16.

A method of assembling the barrel10will now be described with reference toFIGS. 4 and 5. As shown inFIG. 5, a reinforcement member50is integrated into the inner skin12by positioning the first end segment54between the inner skin layers12a,12bsuch that the layers12a,12blie over the first end segment54, and then applying adhesive to adjacent surfaces of the first end segment54and the inner skin layers12aand12b. One or more additional reinforcement members50may also be integrated into the inner skin12at desired locations around the periphery of the inner skin12. Upon integrating the desired number of reinforcement members50into the inner skin12, a sub-assembly10ais formed. The sub-assembly10ais then allowed to cure in a conventional manner. The inner skin12and the first end segment54of each reinforcement member50may thereafter be perforated together, such as by drilling, sand blasting or other known technologies, so as to have aligned perforations18,58.

Turning toFIG. 4, once the sub-assembly10ahas cured and the inner skin12and the first end segments54of the reinforcement members50have been perforated, the core16is bonded to the sub-assembly10ausing a suitable adhesive. In bonding the core16to the sub-assembly10a, the core16is bonded to the reinforcement member50and the inner skin12. After the core16is bonded to the sub-assembly10a, the radially innermost surface14aof the outer skin14is bonded to the core16and the reinforcement member50, thereby completing the barrel10. As indicated above, the bonding techniques employed are well known to those skilled in the art.

According to an alternative embodiment, the inner skin12, outer skin14, cellular core16and reinforcement members50may be bonded together in one step to form the barrel10, and the barrel10may thereafter be allowed to cure. The inner skin12and the first end segment54of each reinforcement member50may then be perforated together so as to have aligned perforations18,58.

FIGS. 6 and 7show a crack and delamination stopper or reinforcement member150according to another embodiment of the invention. The reinforcement member150may be used in place of the reinforcement member50shown inFIGS. 1-5. The reinforcement member150has an essentially C-shaped cross section in the axial direction of the barrel10and includes a central segment152extending in a first direction D1, a first end segment154extending from a first end of the central segment152in a second direction D2transversely to the first direction D1, and a second end segment156extending from a second end of the central segment152in the second direction D2. Each reinforcement member150is constructed from two similarly shaped plies160,170that are bonded together such that each ply160,170essentially forms a half of the reinforcement member150. As is the case with the embodiment ofFIGS. 1-5, the reinforcement member150is provided as a pre-cured composite body.

As shown inFIG. 7, the ply160may be longer than the ply170in the direction D2at the first end segment154in order to promote more secure integration of the reinforcement member150into a barrel100(FIG. 8).

As is the case in the embodiment ofFIGS. 1-5, the reinforcement member150may generally have a thickness T (in the direction perpendicular to the length of a respective portion152/154/156) of about 0.030 to 0.050 inches (0.076-0.127 cm). However, the thickness of the reinforcement member150may vary based upon the requirements of a particular application. Additionally, the reinforcement member150may be formed from a different number of plies, the plies may be joined by means other than bonding, or the reinforcement members may have unitary one-piece construction. The axial length of the reinforcement member150(in the direction L shown inFIG. 1) may be approximately equal to the axial length of the core16.

FIG. 8shows the construction of the barrel100including at least one reinforcement member150. As shown inFIG. 8, the central segment152of the reinforcement member150extends radially in the direction R through the core16of the barrel100, the first end segment154of the reinforcement member150extends substantially parallel to the inner skin12in a first direction X1and the second end segment156of the reinforcement member150extends substantially parallel to the outer skin14in the direction X1. The first end segment154is positioned between layers12a,12bof the inner skin12. The second end segment156is positioned between the radially outermost surface16aof the core16and the radially innermost surface14aof the outer skin14. The second end segment156may alternatively be positioned between individual layers (not shown) of the outer skin14, in a similar fashion to the bonding of the first end segment154between the layers12a,12bof the inner skin12. However, as is the case with the previously described barrel10, it is preferable that the second end segment156not be positioned between individual layers of the outer skin14, so that the bond between the reinforcement member150and the inner skin12is stronger than the bond between the reinforcement member150and the outer skin14. Preferably, when the reinforcement member150is integrated into the barrel100, the first end segment154of the reinforcement member150is provided with perforations158that are aligned with the perforations18in the inner skin12.

The reinforcement member150is integrated into the inner skin12by positioning the first end segment154between the inner skin layers12a,12bsuch that the layers12a,12blie over the first end segment154, and applying adhesive to adjacent surfaces of the first end segment154and the inner skin layers12aand12b. One or more additional reinforcement members150may also be integrated into the inner skin12at desired locations around the periphery of the inner skin12. Upon installing the desired number of reinforcement members150into the inner skin12, a sub-assembly100aincluding the inner skin12and the reinforcement members150is formed. The sub-assembly100ais then allowed to cure. The inner skin12and the first end segment154of each reinforcement member50may thereafter be perforated together so as to have aligned perforations18,158. Once the sub-assembly100ahas cured and the inner skin12and the first end segments154of the reinforcement members150have been perforated, the core16is bonded to the sub-assembly100a, and outer skin14is bonded to the core16using a suitable adhesive. In bonding the core16to the sub-assembly100a, the core16is bonded to the reinforcement members50and the inner skin12. After the core16is bonded to the sub-assembly100a, the radially innermost surface14aof the outer skin14is bonded to the core16and the reinforcement members150, thereby completing the barrel100.

According to an alternative embodiment, the inner skin12, outer skin14, cellular core16and reinforcement members150may be bonded together in one step to form the barrel100, and the barrel100may thereafter be allowed to cure. The inner skin12and the first end segment154of each reinforcement member150may then be perforated together so as to have aligned perforations18,158.

A crack and delamination stopper or reinforcement member250according to another embodiment is shown inFIGS. 9 and 10. When assembled from its components, the reinforcement member250has a substantially I-shaped cross-section in the axial direction of the barrel200and includes an elongate central segment252extending in a first direction D1, a first end segment254extending transversely to the central segment252in directions D2, D3, and a second end segment256extending from a second end of the central segment252transversely in directions D2, D3to the central segment252. The central segment252may include a bowed region252ahaving an arcuate cross-section.

According to a preferred embodiment, the reinforcement member250is provided as a pre-cured composite body constructed of graphite-epoxy or the like. As shown inFIGS. 9 and 10, the reinforcement member250is constructed of a first substantially C-shaped member260and a second substantially C-shaped member270joined together in back-to-back relationship. The first substantially C-shaped member260is formed from two similarly shaped plies262,264that are bonded together. Similarly, the second substantially C-shaped member270is formed from two similarly shaped plies272,274that are bonded together. In order to promote more secure bonding within the barrel200, the plies262,272extend further in the directions D2, D3than the plies264,274. The bowed region252ais formed from bowed regions in the plies262,264and272,274that assist in alignment of the plies.

Referring toFIG. 11, the end segments254,256may generally have a thickness T (in the direction perpendicular to the length of the respective segment254/256) of about 0.5 inches (1.27 cm), while the central segment252may have a thickness T2(in the direction perpendicular to the length of the segment252) of about 1 inch (2.54 cm). However, the thickness of the reinforcement member250may vary as required. The axial length of the reinforcement member250(in the direction L shown inFIG. 1) may be approximately equal to the axial length of the core16.

As is the case with the preceding embodiments, it should be understood that the reinforcement member250may have a different number of multiple plies, the plies may be joined by means other than bonding, or the reinforcement member may have unitary one-piece construction.

FIG. 11illustrates the construction of the barrel200including the reinforcement member250. As shown inFIG. 11, the central segment252of the reinforcement member250extends radially in the direction R through the core16of the barrel200, the first end segment254of the reinforcement member250extends substantially parallel to the inner skin12in directions X1, X2and the second end segment256of the channel member50extends substantially parallel to the outer skin14in directions X1, X2. The first end segment254is positioned between opposing layers12a,12bof the inner skin12, and the second end segment256is positioned between the radially innermost surface14aof the outer skin14and the radially outermost surface16aof the core16. Optionally, the second end portion256of the reinforcement member250may be positioned between individual layers (not shown) of the outer skin14. As in the previously discussed barrels10,100, it is less preferable to position the second end portion256between individual layers of the outer skin14, as it is desirable that the bond between the reinforcement member250and the inner skin12be stronger than the bond between the reinforcement member250and the outer skin14. When the reinforcement member250is integrated into the barrel200, the first end segment254of the reinforcement member250is preferably provided with perforations258that are substantially aligned with the perforations18in the inner skin12.

The reinforcement member250is integrated into the inner skin12by positioning the first end segment254between the inner skin layers12a,12bsuch that the layers12a,12blie over the first end segment254, and applying adhesive to adjacent surfaces of the first end segment254and the inner skin layers12a,12b. One or more additional reinforcement members250may also be integrated into the inner skin12at desired locations around the periphery of the inner skin12. Upon installing the desired number of reinforcement members250into the inner skin12, a sub-assembly200aincluding the inner skin12and the reinforcement members250is formed. The sub-assembly200ais then allowed to cure. The inner skin12and the first end segment254of each reinforcement member250may then be perforated together so as to have aligned perforations18,258. Once the sub-assembly200ahas cured, and the inner skin12and the first end segments254of the reinforcement members250have been perforated, the core16is bonded to the sub-assembly200a. In bonding the core16to the sub-assembly200a, the core16is bonded to the reinforcement members250and the inner skin12. After the core16is bonded to the sub-assembly200a, the radially innermost surface14aof the outer skin14is bonded to the core16and the reinforcement members250.

According to an alternative embodiment, the inner skin12, outer skin14, cellular core16and reinforcement members250may be bonded together in one step to form the barrel200, and the barrel200may thereafter be allowed to cure. The inner skin12and the first end segment254of each reinforcement member250may then be perforated together so as to have aligned perforations18,258.

FIG. 12shows one embodiment of an assembled, complete aircraft propulsion assembly300andFIG. 13shows an exploded view of the aircraft propulsion assembly ofFIG. 12. As seen inFIG. 13, the principal components of the aircraft propulsion system include an engine assembly302at the tail end of which are an exhaust cone304and an exhaust nozzle306. The forward end of the engine assembly302is provided with a nacelle inlet310having a nacelle inlet lip312. It is understood that the nacelle inlet310may be of the sort having reinforcement members, as described above. Aft of the nacelle inlet310is fan cowl320comprising fan cowl halves322,324. A thrust reverser330comprising thrust reverser halves332,334is aft of the fan cowl320. Finally, a pylon/strut assembly340connects the aforementioned component to a wing of an aircraft.

FIGS. 14,15and16show details of a thrust reverser400representative of the thrust reverser330seen inFIGS. 12 and 13. The thrust reverser400includes an outer fixed structure410, a translating sleeve500, and an inner fixed structure810.

The outer fixed structure410is provided with such features as a fan cowl land460, an outer groove472mated to the engine assembly302and other forward components in the assembled system. Also provided on the outer fixed structure410is a torque box assembly440and a plurality of actuators430which are operatively connected to the translating sleeve500. Cascades450, which terminate in the aft direction at an aft cascade attached frame452, are provided on the outer fixed structure410to selectively redirect fan exhaust depending on the mode (forward or reverse) of the thrust reverser400.

The translating sleeve500includes an outer panel assembly510, an inner panel assembly512, lower inner and outer sliders522,524, and upper inner and outer sliders526,528. An inner circumferential periphery of the sleeve500is provided with a plurality of hinged blocker doors530arranged side-by-side. Each blocker door530is connected via a blocker door link532to a hinged mount534affixed to an outer portion of the inner fixed structure810. The translating sleeve500is further connected to the inner fixed structure810by the lower inner and outer sliders522,524and the upper inner and outer sliders526,528which engage tracks560belonging to the inner fixed structure810. The inner panel assembly512is locally flattened in a predetermined region544to attach the inner sliders. When the blocker doors530are closed (forward thrust mode), they cover the cascades450and when the blocker doors530are open (reverse thrust mode), the cascades are no longer covered and so permit fan exhaust to pass therethrough.

The translating sleeve500moves between a first position in which the thrust reverser400is in forward thrust mode and a second position in which the assembly is in the reverse thrust mode. The actuators430mounted on the outer fixed structure410cause the translating sleeve500to move between the first and second positions. In the forward thrust mode, the translating sleeve500forms the nacelle external surface and shields the cascades450from exhaust gases. In the reverse thrust mode, the translating sleeve500slides in the aft direction. This deploys the blocker doors530, exposes the cascades450, and redirects fan exhaust in a forward direction.

Prior art thrust reverser inner fixed structures having portions comprising an inner skin, and outer skin and a cellular core, which may be an acoustic cellular core, are known. In such constructions, the inner and outer skins are bonded to the cellular core. However, disbonding of the inner or outer skin from the core has been an issue in the nacelle industry, in some instances resulting in parts of the inner fixed structure detaching and even departing from the aircraft. Disbonding may result from the degradation of the bond line between the cellular core and one or more of the inner skin and outer skin due to long exposure to high temperatures of the sort created by exhaust gases. Regardless of the causes for disbonding, providing a thrust reverser inner fixed structure with reinforcement members, such as those discussed above with respect to an inner barrel, may be one way to mitigate the effects of disbonding with minimal added cost and weight.

FIG. 17shows a thrust reverser half332awhich exposes one half section890(“IFS Section”) of an inner fixed structure formed in two “clam-shell” halves, only one clam-shell half890being shown. It is understood that the unseen second section is essentially a mirror image of seen section890. The IFS section has a forward end860which faces in the direction of the engine and fan cowl and an aft end862which faces in the direction of the exhaust nozzle. The IFS halves890are connected together by latches870at the bottom and hinged to the pylon340at the top. Bumpers480provide a structural bridge between the gaps that separates the two IFS halves890. The structural bridge provides a hoop load path to resist the crushing pressure of the fan air stream upon the barrel sections and bifurcations.

The inner fixed structure seen inFIG. 17is constructed to encase portions of the engine assembly located between the engine fan case and the nozzle. The inner fixed structure is configured to create an aerodynamically smooth path for air and creates a fire and heat boundary by enclosing portions of the engine assembly.

In one embodiment, the inner fixed structure section890is a one-piece honeycomb sandwich comprising an inner skin, an outer skin and a cellular core between the inner and outer skins, all bonded together. The honeycomb sandwich is typically an acoustic structure with an imperforate inner skin820, a perforated outer skin822, and a cellular core824suitable for use in acoustic applications. The inner skin820may be formed from a metallic or a graphite composite material; the outer skin may also be formed from a metallic or graphite composite material; and the cellular core824may be formed from a metallic material such as aluminum or titanium, or may even be formed from a non-metallic material, such as a graphite composite material.

The inner fixed structure section890has an upper bifurcation wall portion802, a lower bifurcation wall portion804and a barrel portion806formed between the two wall portions802,804. The honeycomb sandwich is acoustic wherever possible to control noise, but is interrupted by a number of structures and formations such as cooling holes812, bumpers480, latches870, mounting members and the like.

Aft of its forward end860where it interfaces with the fan section, the diameter of the barrel portion806increases to form an enlarged barrel portion808of suitable size and shape to enclose the rear engine mounts and the turbine section of the engine. The barrel portion806then decreases in diameter to wrap around the forward portion of the exhaust nozzle306.

To help prevent disbonding, the honeycomb sandwich, in at least the enlarged barrel portion808of the inner fixed structure section890is provided with a reinforcement lattice815. In some embodiments, the reinforcement lattice is provided only in the enlarged barrel portion808. The reinforcement lattice815comprises a plurality of reinforcement members817,819extending in a thickness direction through the cellular core824between the “back” or inner skin820and the outer skin822. Reinforcement members817, which extend in a first direction, constitute a first set of reinforcement members, while reinforcement members819, which extend in a second direction, constitute a second set of reinforcement members, the two directions intersecting.

Each of the reinforcement members also extends in lateral direction through the cellular core824, the lateral directions being perpendicular to the thickness direction of the cellular core824. The lateral directions associated with a first set of reinforcement members817intersect lateral directions associated with a second set of reinforcement members819to thereby form the reinforcement lattice815.

As seen with the reinforcement lattice815ofFIG. 17, the reinforcement members themselves may intersect. In some embodiments, at the intersections, a first reinforcement member may be broken while a second reinforcement member continues unbroken. In such case, the broken reinforcement member may be bonded to transversely extending opposite side walls of the unbroken reinforcement member. In other embodiments, at the intersections, special “cross-shaped” intersection members may be provided, with the “broken” ends of the two intersecting reinforcement members being bonded to legs of the “cross-shaped” intersection members.”

As seen in the embodiment ofFIG. 17, at least two longitudinal reinforcement members817extend along a longitudinal direction of the inner fixed structure section890, while at least two circumferential reinforcement members819extend along a circumferential direction of the inner fixed structure section890. Furthermore, as seen in this figure, the longitudinal reinforcement members817intersect the circumferential reinforcement members819to form the reinforcement lattice815.

It is understood that in a complete thrust reverser inner fixed structure810, two complementary sections890are arranged in a clamshell configuration, each section including such a reinforcement lattice815. It is further understood that one may instead form a one-piece thrust reverser inner fixed structure (not shown) which may have two such reinforcement lattices815facing each other in the enlarged barrel portion808.

As seen inFIGS. 18A, and18B, the reinforcement members830,840may take on different cross-sectional shapes.

As seen inFIG. 18A, T-shaped cross-sectional member830has a central segment832having a first end836and a second end838. The central segment832extends radially through the cellular core824and is connected at its first end836to a first end segment834. The first end segment834extends substantially parallel to the inner skin820and is bonded thereto, such as in the manner described previously with respect to the inner barrel. In addition, the central segment832is bonded to cellular core824by adhesive bonding, by diffusion bonding, or in some other manner. In the case of adhesive bonding, a foam adhesive may be employed. Thus, the central segment832is anchored to the cellular core824while the first end segment834is anchored to the inner skin820. However the outer skin822typically is not bonded to the reinforcement member830and, in some embodiments the second end838of the central segment832may not even extend to the outer skin822and so the reinforcement member830may be spaced apart therefrom.

In some embodiments, the central segment832of the T-shaped cross-sectional member has a thickness of about 0.044 inches while the first end segment834of the T-shaped cross-sectional member has a thickness of about 0.022 inches. Thus, the T-shaped cross-sectional member830may be formed by folding a sheet of material having a thickness of about 0.022 inches on itself to form the central segment832, and further fold the ends outwardly to create a T-shaped cross-section. The folded sheet may then be pre-cured before incorporation into the cellular core824. Alternatively, in some embodiments, the folded sheet may be co-cured with the inner and/or outer skins.

As seen inFIG. 18B, L-shaped cross-sectional member840has a central segment842having a first end846and a second end848. The central segment842extends radially through the cellular core824and is connected at its first end846to a first end segment844. The first end segment844extends substantially parallel to the inner skin820and is bonded thereto, such as in the manner described previously with respect to the inner barrel. In addition, the central segment842is bonded to cellular core by adhesive bonding, by diffusion bonding, or in some other manner. In the case of adhesive bonding, a foam adhesive may be employed. Thus, the central segment842is anchored to the cellular core824while the first end segment844is anchored to the inner skin820. However the outer skin822typically is not bonded to the reinforcement member840and, in some embodiments the second end848of the central segment842may not even extend to the outer skin822and so the reinforcement member840may be spaced apart therefrom.

In some embodiments, the central segment842and the first end segment844of the L-shaped member both have a thickness of 0.022 inches. Thus, the L-shaped cross-sectional member840may be formed by folding a sheet of material having a thickness of about 0.022 inches to create an L-shaped cross-section. The folded sheet may then be pre-cured before incorporation into the cellular core824. Alternatively, in some embodiments, the folded sheet may be co-cured with the inner and/or outer skins.

WhileFIGS. 18A and 18Bshow cross-sections of two specific embodiments of reinforcement members, it is understood that reinforcement members may have some other cross-section, such as an I-shape, a C-shape, a Z-shape, as described above. Typically, in all such embodiments, the first end segment is bonded to the inner skin and the central segment is bonded to the cellular core. However, the outer skin may not be bonded to the reinforcement member, even though the second end of the central segment of the reinforcement member is proximate to an inner surface of the outer skin. In such case, the “second end segment” proximate the second end of the central section is adhesively anchored to the core824, thereby providing additional surface area to resist disbonding.

The embodiments disclosed herein improve the fly-home capability of aircraft during blade-out events, disbonding events and other events that may inflict damage on aircraft propulsion system components, such as the acoustic inner barrel of an aircraft engine nacelle or the inner fixed structure of a thrust reverser. When such an event severely impacts such a component, the disclosed reinforcement members function to limit crack propagation and/or disbonding. And due to their design and orientation, the reinforcement members also should not significantly affect the sound dampening performance of these components.

The foregoing disclosure provides illustrative embodiments of the invention and is not intended to be limiting. It should be understood that modifications of the disclosed embodiments are possible within the spirit and scope of the invention, and the invention should be construed to encompass such modifications.