Laminar flow panel

An aerodynamic body operable to both promote laminar flow and satisfy structural requirements is disclosed. A perforated panel skin comprises an inner surface and an outer surface of the aerodynamic body. At least one hollow member is coupled to the inner surface and is operable to suction air from the outer surface and through the perforated panel skin. The at least one hollow member is oriented in a substantially chord-wise direction relative to an airflow over the aerodynamic body.

FIELD

Embodiments of the present disclosure relate generally to aerodynamic surfaces. More particularly, embodiments of the present disclosure relate to aerodynamic surfaces providing laminar flow.

BACKGROUND

Laminar flow comprises, for example but without limitation, a smooth low turbulence flow of air over a contour of parts of an aircraft such as wings, fuselage, and the like. The term laminar flow is derived from a process where layers of air are formed one next to the other in formation of a boundary layer. Interruption of a smooth flow of boundary layer air over a wing section can create turbulence, which may result in non-optimal lift and/or non-optimal drag. An aerodynamic body designed for minimum drag and uninterrupted flow of the boundary layer may be called a laminar aerodynamic surface. A laminar aerodynamic surface may maintain an adhesion of boundary layers of airflow as far aft of a leading edge as practical. On non-laminar aerodynamic bodies, a boundary layer may be interrupted at high speeds and result in turbulent flow over a remainder of the non-laminar aerodynamic surface. This turbulent flow may be realized as drag, which may be non-optimal.

SUMMARY

An aerodynamic body operable to both promote laminar flow and satisfy structural requirements is disclosed. A perforated panel skin comprises an inner surface and an outer surface. The outer surface comprises a leading edge of the aerodynamic body. The inner surface is stiffened by at least one hollow member coupled thereon. The at least one hollow member is oriented in a substantially chord-wise direction relative to an airflow over the aerodynamic body and is operable to suction air from the outer surface.

In a first embodiment, an aerodynamic body comprises a perforated panel skin comprising an outer surface and an inner surface of the aerodynamic body. The aerodynamic body further comprises at least one hollow member coupled to the inner surface and operable to suction air from the outer surface through the perforated panel skin. The at least one hollow member is oriented in a substantially chord-wise direction relative to an airflow over the aerodynamic body.

In a second embodiment, a method provides a corrugation-stiffened structure. The method provides a perforated panel skin comprising an outer surface and an inner surface of an aerodynamic body. The method further provides a stiffener comprising at least one hollow member coupled to the inner surface, and orients the at least one hollow member in a substantially chord-wise direction relative to an airflow over the aerodynamic body.

In a third embodiment, a method provides laminar flow over an aerodynamic body. The method stiffens an inner surface of a perforated panel skin of the aerodynamic body with at least one hollow member coupled to the inner surface. The method further orients the at least one hollow member substantially in a chord-wise direction relative to an airflow over the aerodynamic body. The method then suctions at least one portion of the airflow through an outer surface of the perforated panel skin, and draws the at least one portion of the airflow through the at least one hollow member.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is not intended to limit the disclosure or the application and uses of the embodiments of the disclosure. Descriptions of specific devices, techniques, and applications are provided only as examples. Modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the disclosure. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding field, background, summary or the following detailed description. The present disclosure should be accorded scope consistent with the claims, and not limited to the examples described and shown herein.

Embodiments of the disclosure may be described herein in terms of functional and/or logical block components and various processing steps. It should be appreciated that such block components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For the sake of brevity, conventional techniques and components related to aerodynamics, structures, manufacturing, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail herein. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with a variety of structural bodies, and that the embodiments described herein are merely example embodiments of the disclosure.

Embodiments of the disclosure are described herein in the context of practical non-limiting applications, namely, an airfoil leading edge. Embodiments of the disclosure, however, are not limited to such airfoil leading edge applications, and the techniques described herein may also be utilized in other aerodynamic surface applications. For example, embodiments may be applicable to tail structures, engine struts, wind turbine blades, hydrodynamic surfaces utilizing liquid (e.g., water) instead of air, and the like.

As would be apparent to one of ordinary skill in the art after reading this description, the following are examples and embodiments of the disclosure and are not limited to operating in accordance with these examples. Other embodiments may be utilized and structural changes may be made without departing from the scope of the exemplary embodiments of the present disclosure.

Referring more particularly to the drawings, embodiments of the disclosure may be described in the context of an aircraft manufacturing and service method100as shown inFIG. 1and an aircraft200as shown inFIG. 2. During pre-production, the exemplary method100may include specification and design104of the aircraft200and material procurement106. During production, component and subassembly manufacturing108and system integration110of the aircraft200takes place. Thereafter, the aircraft200may go through certification and delivery112in order to be placed in service114. While in service by a customer, the aircraft200is scheduled for routine maintenance and service116(which may also include modification, reconfiguration, refurbishment, and so on).

As shown inFIG. 2, the aircraft200produced by the exemplary method100may include an airframe218with a plurality of systems220and an interior222. Examples of high-level systems220include one or more of a propulsion system224, an electrical system226, a hydraulic system228, and an environmental system230. Any number of other systems may also be included. Although an aerospace example is shown, the embodiments of the disclosure may be applied to other industries.

Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method100. For example, components or subassemblies corresponding to production process108may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft200is in service. In addition, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages108and110, for example, by substantially expediting assembly of or reducing the cost of an aircraft200. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft200is in service, for example and without limitation, to maintenance and service116.

Embodiments of the disclosure provide for enabling and maintaining laminar flow over airplane external surfaces utilizing a Hybrid Laminar Flow Control, thereby reducing skin friction drag. Hybrid Laminar Flow Control may refer to a strategic application of suction through small holes in a leading-edge region of a surface such as a wing to remove instabilities that may cause airflow near a surface to transition from a laminar to a turbulent state.

FIG. 3is an illustration of a vertical fin cross section300without Hybrid Laminar Flow Control showing turbulent flow304near a surface302. As shown inFIG. 3, the turbulent flow304near the surface302is fully turbulent, thereby creating a high skin friction drag.

FIG. 4is an illustration of a vertical fin cross section400(airfoil400) comprising a laminar flow corrugation-stiffened bonded structure402(corrugation-stiffened structure402) providing Hybrid Laminar Flow Control according to an embodiment of the disclosure. A suction area404of the corrugation-stiffened structure402creates a laminar flow406near an airfoil surface408. The suction area404is perforated to allow air to flow through the airfoil surface408, and stiffened to maintain shape while allowing the airflow to occur. Embodiments of the corrugation-stiffened structure402are described below in the context ofFIGS. 8-20.

Embodiments of the disclosure provide a panel structure that enables laminar flow over at least a portion of external surfaces such as the external surfaces of an aircraft500(FIG. 5) and maintains a laminar boundary layer on exterior aerodynamic surfaces as shown inFIGS. 5-7.

FIG. 5is an illustration of the aircraft500showing various external structures, such as but without limitation, the vertical fin504, a horizontal stabilizer506, an engine nacelle508, leading edge control surfaces510(i.e., flap and spoilers), and the like, that can be subject to laminar flow.

FIG. 6is an illustration of a tail section600of the aircraft500showing approximate regions of laminar flow602and604on the vertical fin504and the horizontal stabilizers506respectively.

FIG. 7is an illustration of a wing502of the aircraft500showing approximate regions of laminar flow702and704on the leading edge control surfaces510and on the engine nacelle508respectively.

FIG. 8is an illustration of a perspective view of an exemplary laminar flow corrugation-stiffened bonded structure800(corrugation-stiffened structure800) according to an embodiment of the disclosure. The corrugation-stiffened structure800may be an aerodynamic body comprising, for example but without limitation, a flat panel, a curved leading edge, and the like. The corrugation-stiffened structure800comprises a perforated panel skin802, one or more corrugated stiffeners804, a strap806, an edgeband808, and one or more ends810of the corrugated stiffeners804.

The perforated panel skin802allows for passively suctioning air902(FIG. 9) from an outer surface908(FIG. 9) to an inner surface910(FIG. 9) of the corrugation-stiffened structure800via a plurality of perforations/holes812to facilitate laminar flow over external aerodynamic surfaces such as, but without limitation, the vertical fin504, the horizontal stabilizer506, the engine nacelle508, the leading edge control surfaces510, and the like (FIGS. 5-7). The perforated panel skin802may be made of, for example but without limitation, carbon fiber-reinforced polymer (CFRP)/CP2 titanium, and the like. A thickness1508(FIG. 15) of the perforated panel skin802may be, for example but without limitation, about 0.04 inches to about 0.063 inches, and the like.

The perforations/holes812are, for example but without limitation, suitably spaced, shaped, drilled (e.g., laser-drilled), and the like to allow an appropriate amount of passive-suction of air from the outside surface908to the inner surface910while maintaining laminar flow surfaces sufficiently smooth. In this manner, the perforated panel skin802is suitably perforated to allow air to flow therethrough, and is stiffened, as explained in more detail below, to maintain its shape while allowing the airflow to occur. A number of the perforations/holes812used may depend on, for example but without limitation, flight speed, local Mach number, structural integrity, aerodynamic requirements, and the like. For example but without limitation, in a subsonic flight, a suitable number of the perforations/holes812can be provided to drop a surface pressure of the external aerodynamic surfaces by about one psi for passively moving the air902from the outer/external surface908to the inner surface910. In this manner, laminar flow over the external aerodynamic surfaces is facilitated.

The corrugated stiffeners804are formed to stiffen the panel/corrugation-stiffened structure800. The corrugated stiffeners804comprise corrugated or wave-shaped composite stiffeners which are bonded (FIG. 15) to the inner surface910(FIG. 9) of the corrugation-stiffened structure800. For example, adhesively bonding the corrugated stiffeners804to the inner surface910precludes a need for traditional fasteners. Fasteners may disrupt the airflow over the external aerodynamic surfaces, reducing or negating laminar flow benefits. In the embodiment shown inFIG. 8, the corrugated stiffeners804are located on an upper inner surface828and a lower inner surface830of the inner surface910of the corrugation-stiffened structure800. In the embodiment shown inFIG. 8, one or more hollow members818coupled to each of the upper inner surface828and the lower inner surface830stiffen the leading edge308/814. In the embodiment shown inFIG. 8, the corrugated stiffeners804are formed in two pieces. An upper piece822and a lower piece824are detached from the leading edge308/814to facilitate manufacturing of the corrugated stiffeners804. In this manner, the upper piece822and the lower piece824of the corrugated stiffeners804are not extended through the leading edge308/814, and are coupled to each other by the strap806as explained below.

However, in another embodiment, the corrugated stiffeners804are extended to the leading edge308/814(1902FIG. 19), thereby the strap806is not used. In this manner, a suitable composite material is utilized, as explained below, to allow fabrication of the corrugated stiffeners804around the leading edge308/814as one continuous piece.

In one embodiment, the corrugated stiffeners804are oriented in a substantially chord-wise direction306(FIG. 3) of the leading edge308/814, relative to a downstream airflow310over the airfoil400, and substantially perpendicular to the leading edge308/814. Chord-wise orientation of the corrugated stiffeners804is more efficient structurally, spanning between a stiff nose of the leading edge308/814and an auxiliary spar (not shown). However, various shapes may be used for the corrugated stiffeners804depending on, for example but without limitation, various pressure zones on the external aerodynamic surfaces (FIGS. 5-7). The corrugated stiffeners804may be, for example but without limitation, hexagonal, V-shape, and the like. In order to meet aerodynamic porosity requirements while still maintaining structural integrity at substantially all loads and environmental conditions, bonded joints1502(FIG. 15) can be configured to block a substantially minimum number of the perforations/holes812on the perforated panel skin802. In this manner, airflow passes through the perforated panel skin802and around the corrugated stiffeners804to a low-pressure passive aft-facing vent as explained below in more detail in the context of discussion ofFIG. 9.

The corrugated stiffeners804may be made from, for example but without limitation, CP-2 titanium, one ply of 0/+−60 BMS9-223 braided carbon fiber-reinforced polymer, or the like. An orientation of a braid may be such that about 50% of the carbon fibers are in the substantially chord-wise direction306for structural efficiency. This may also be easier to fabricate, as 60-degree fibers may bend around sharp corners better than 90-degree fibers. The corrugated stiffeners804can provide the leading edge308/814with adequate bending stiffness, smoothness, and waviness to meet operational requirements. In addition, the corrugated stiffeners804enable good bonding to the perforated panel skin802. The good bonding can mitigate current methods where parts may be held substantially rigid during assembly by vacuum-chuck bond assembly tools and bonding between two rigid bodies may be non-optimized due to achievable part tolerances. The corrugated stiffeners804and corrugation-stiffened structure800are as lightweight as possible in order to meet overall airplane efficiency demands.

As mentioned above, in one embodiment, the corrugated stiffeners804are formed in one-piece (1902inFIG. 19) continuously on the inner surface910providing full stiffeners extended to and around the leading edge308/814. In this manner, the corrugated stiffeners804are substantially lightweight and may utilize a formable structure such as, for example but without limitation, a carbon fiber-reinforced polymer utilizing “broken carbon fiber”, Stretch-Broken Carbon Fiber, and the like. However, as mentioned above, the corrugated stiffeners804may be alternatively formed from two or more pieces. Thus, a carbon fiber-reinforced polymer braid that may not be formed into a tight “nose” radius may be formed in two or more pieces as explained above. An exemplary geometric shape of the corrugated stiffeners804is shown in more detail inFIG. 11below.

The strap806couples the upper piece822and the lower piece824of the corrugated stiffeners804to each other. The strap806conforms to the corrugated stiffeners804at ridges1102(FIG. 11) but still allows airflow. In the embodiment shown inFIG. 8, the strap806does not touch the perforated panel skin802. The strap806may be made from, for example but without limitation, CP1 titanium, and the like, having a thickness of, for example but without limitation, about 0.03 inches to about 0.06 inches, and the like. The strap806is bonded in an area near the leading edge814to provide stiffness and strength to the corrugation-stiffened structure800. The strap806may comprise, for example but without limitation, a smooth surface as shown inFIG. 8, a corrugated surface such as a corrugated leading edge strap1604as shown inFIG. 16, and the like. The corrugated leading edge strap1604provides continuity between the upper piece822and the lower piece824of the corrugated stiffeners804so that the upper piece822and the lower piece824communicate air.

The edgeband808is coupled to the perforated panel skin802and the corrugated stiffeners804. The edgeband808couples the corrugation-stiffened structure800to a substructure (not shown) and acts as a plenum chamber to receive air from the corrugated stiffeners804. The edgeband808may be made from, for example but without limitation, fiberglass, aramid fiber, carbon fiber, aluminum, and the like.

The ends810(outlets810) of the corrugated stiffeners804allow air to exit therethrough. The ends810provide an outlet for the hollow members818to flow air902(FIG. 9) to the edgeband808/plenum chamber. The ends810may be shaped, for example but without limitation, triangular, circular, rectangular, and the like. Angles820of the ends810are provided such that stress concentration at the ends810is prevented.

Current honeycomb sandwich leading edge architectures may not be amenable to incorporation of the hybrid laminar flow. Current honeycomb sandwich panels also: 1) tend to absorb and retain moisture; 2) may be non-optimal for inspection; and 3) may be less optimal for repair than the corrugation-stiffened structure800.

FIG. 9is an illustration of an enlarged view of a section900of the corrugation-stiffened structure800showing an airflow according to an embodiment of the disclosure. The air902flows through the perforated panel skin802, continues to flow along the hollow members818of the corrugated stiffeners804, and exits from the ends810(outlets810) of the corrugated stiffeners804. In this manner, the corrugation-stiffened structure800provides for a low-pressure passive aft-facing vent to allow a sufficient amount of air suction for maintaining a laminar boundary layer on the perforated panel skin802, while providing a stiff skin such as the perforated panel skin802.

FIGS. 10-13illustrate exemplary geometric shapes of the corrugation-stiffened structure800.FIGS. 10-13may have functions, material, and structures that are similar to the embodiments shown inFIGS. 1-12. Therefore, common features, functions, and elements may not be redundantly described here.

FIG. 10is an illustration of a cross section1000of the exemplary corrugation-stiffened structure800showing the corrugated stiffeners804, the edgeband808, and the ends810according to an embodiment of the disclosure.

FIG. 11is an illustration of a section A-A816of the corrugated stiffeners804of the corrugation-stiffened structure800shown inFIG. 10showing a wave-like shape comprising ridges1102of the corrugated stiffeners804according to an embodiment of the disclosure.

FIG. 12is an illustration of an enlarged view of a section B-B1002of the exemplary corrugation-stiffened structure800shown inFIG. 10showing the edgeband808and the ends810, according to an embodiment of the disclosure.

FIG. 13is an illustration of an enlarged view of a section C-C1004of the exemplary corrugation-stiffened structure800shown inFIG. 10showing the corrugated stiffeners804and the leading edge814according to an embodiment of the disclosure.

FIG. 14is an illustration of a top view1400of an exemplary rib stiffener1404of the corrugation-stiffened structure800showing an adhesive1402placed on the rib stiffener1404according to an embodiment of the disclosure. In this manner, each of the rib stiffener1404receives the adhesive1402at each of the bonded joints1502(stiffener node) shown inFIG. 15.

FIG. 15is an illustration of a cross sectional view of an exemplary stiffener of the corrugation-stiffened structure800showing a stiffener/stiffener bond1506and a stiffener/titanium bond at the bonded joint1502according to an embodiment of the disclosure. As mentioned above, the bonded joints1502block a substantially minimum number of the perforations/holes812of the perforated panel skin802, while allowing airflow therethrough and around the corrugated stiffeners804to a low-pressure passive aft-facing vent as explained above in more detail in the context of discussion ofFIG. 9. Accurate control of bond-line width1504enables substantially precise control of the perforations/holes812blocked by the adhesive1402. In this manner, embodiments of the disclosure provide a stiffening of the perforated panel skin802while maintaining a substantially precise air transfer necessary for providing laminar flow. The corrugated stiffeners804are bonded to the perforated panel skin802with, for example but without limitation, a 250F-cure film adhesive in an oven. Alternatively, the corrugated stiffeners804may be bonded to the perforated panel skin802by methods, such as but without limitation, thermal or ultra-sonic joining (i.e., for thermoplastic stiffeners), and the like. The bonded joint1502can be inspected by an inspection method, such as but without limitation, ultrasonic, optical, thermographic non-destructive inspection, and the like. The bond-line width1504of the bonded joint1502may be, for example but without limitation, about 0.14 to about 0.16 inches, and the like.

FIGS. 16-19may have functions, material, and structures that are similar to the embodiments shown inFIGS. 1-15. Therefore common features, functions, and elements may not be redundantly described here.

FIG. 16is an illustration of a perspective view of an exemplary corrugation-stiffened structure1600showing the corrugated leading edge strap1604according to an embodiment of the disclosure. The corrugation-stiffened structure1600comprises a leading edge tip1602, the corrugated leading edge strap1604, one or more upper corrugated stiffeners1606coupled to the inner surface1612, one or more lower corrugated stiffeners1608coupled to the inner surface1612, and one or more ends1610.

As shown inFIG. 16, the corrugated leading edge strap1604couples the upper and lower corrugated stiffeners1606/1608(similar to the upper piece822and the lower piece824of corrugated stiffeners804inFIG. 8) to each other. In the embodiment shown inFIG. 16, the corrugated leading edge strap1604is configured to be detached from an area of the inner surface1612of the corrugation-stiffened structure1600near the leading edge tip1602.

FIG. 17is an illustration of an enlarged view1700of a portion of the exemplary corrugation-stiffened structure1600showing the upper and lower corrugated stiffeners1606/1608coupled to each other by a corrugated leading edge strap1604bonded at front ends1702of the upper and lower corrugated stiffeners1606/1608according to an embodiment of the disclosure.

FIG. 18is an illustration of an enlarged view of a portion1800of the exemplary corrugation-stiffened structure1600according to an embodiment of the disclosure. As shown inFIG. 18the corrugated leading edge strap1604conforms to ridges1802of the upper and lower corrugated stiffeners1606/1608but still allows air flow906(FIG. 9).

FIG. 19is an illustration of an enlarged view of a portion of an exemplary one-piece corrugation-stiffened structure1900showing the corrugated stiffeners1902bonded to the inner surface1612at a bonding area1904at the leading edge1906according to an embodiment of the disclosure. The corrugated stiffeners1902are one-piece and continuous around the leading edge1906(1602inFIG. 16). Since the corrugated stiffeners1902are one-piece and continuous around the leading edge308/814, a strap such as the corrugated leading edge strap1604is not used. In this manner, the perforations/holes812(FIG. 8) may be cut/drilled into the corrugated stiffeners1902around the leading edge1906(e.g., if the openings of the ends810/1610are not sufficient).

FIG. 20is an illustration of a cross section2000of corrugated stiffeners2002and a corrugated strap2004of an exemplary corrugation-stiffened structure1600according to an embodiment of the disclosure. As shown inFIG. 20, the corrugated strap2004couples the corrugated stiffeners2002to each other. The corrugated strap2004conforms to the inner surface1612(FIG. 16) and comprises ridges2008located, for example but without limitation, about 1.0 inch to about 1.2 inches apart.

FIG. 21is an illustration of an exemplary flow chart showing a process2100for providing a corrugation-stiffened structure800/1600for providing a laminar flow on a leading edge of an airfoil according to an embodiment of the disclosure. The various tasks performed in connection with process2100may be performed mechanically, by software, hardware, firmware, or any combination thereof. For illustrative purposes, the following description of process2100may refer to elements mentioned above in connection withFIGS. 1-20. In practical embodiments, portions of the process2100may be performed by different elements of the corrugation-stiffened structure800such as the perforated panel skin802, the corrugated stiffeners804, the strap806, the edgeband808, and the ends810of the corrugated stiffeners804. Processes2100may have functions, material, and structures that are similar to the embodiments shown inFIGS. 1-20. Therefore common features, functions, and elements may not be redundantly described here.

Process2100may begin by providing a perforated panel skin such as the perforated panel skin802comprising the outer surface908and the inner surface910of an aerodynamic body such as the airfoil400(task2102).

Process2100may then continue by providing the corrugated stiffener804comprising the at least one hollow member818coupled to the inner surface910(task2104).

Process2100may then continue by orienting the at least one hollow member818in the substantially chord-wise direction306relative to the downstream airflow310over the aerodynamic body (task2106).

FIG. 22is an illustration of an exemplary flow chart showing a process2200for providing a corrugation-stiffened structure800/1600and for providing a laminar flow on a leading edge of an airfoil according to an embodiment of the disclosure. The various tasks performed in connection with process2200may be performed mechanically, by software, hardware, firmware, or any combination thereof. For illustrative purposes, the following description of process2200may refer to elements mentioned above in connection withFIGS. 1-20. In practical embodiments, portions of the process2200may be performed by different elements of the corrugation-stiffened structure800/1600such as the perforated panel skin802, the corrugated stiffeners804, the strap806, the edgeband808, and the ends810of the corrugated stiffeners804. Process2200may have functions, material, and structures that are similar to the embodiments shown inFIGS. 1-20. Therefore common features, functions, and elements may not be redundantly described here.

Process2200may begin by stiffening the inner surface910of the perforated panel skin802of the corrugation-stiffened structure800(aerodynamic body) with the at least one hollow member818coupled to the inner surface910(task2202).

Process2200may then continue by orienting the at least one hollow member818in the substantially chord-wise direction306relative to an airflow such as the downstream airflow310over the aerodynamic body (task2204).

Process2200may then continue by suctioning at least one portion of the downstream airflow310through the outer surface908of the perforated panel skin802of the aerodynamic body (task2206).

Process2200may then continue by drawing the at least one portion of the downstream airflow310through the at least one hollow member818(task2208).

In this way, various embodiments of the disclosure provide a method for stiffening of a skin of an aerodynamic body while maintaining a substantially precise air transfer necessary to maintain laminar boundary layer over the aerodynamic body. The embodiments allow airflow through a leading edge structure, which allows for laminar flow on the surface thereof, while still maintaining the required aerodynamic shape also necessary for the laminar flow. Maintaining the laminar flow, results in a large aerodynamic drag reduction as compared to tradition turbulent flow found on most commercial aircraft in service today. In addition, corrugation-stiffened structure800, allows easy inspection of surfaces, may not substantially entrap moisture, is repairable via a bonded corrugated doubler easy to inspect and can be made in a variety of materials and material combination and could be used to replace honeycomb sandwich in many non-laminar-flow applications.