Aircraft window erosion shield

(54) Title: AIRCRAFT WINDOW TABLE (57) Abstract: COMPOSITE.

(30) Unionist Priority: 12/01/2007 US60 / 880,100 (73) Holder (s): The Nordam Group, INC.

(72) Inventor (s): Kevin Steven Jackson, SCOTT ERNEST

OSTREM, STEPHEN FREDERICK JOSEPH WALLACE (74) Attorney (s): Alexandre Ferreira (86) International Application: pct US2008000326 of 01/09/2008 (87) International Publication: wo 2008 / 088708de 24/07/2008

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“COMPOSED AIRCRAFT WINDOW FRAME”

Field of the Invention

The present invention generally relates to aircraft, and, more specifically, their windows.

Fundamentals of the Invention

In a typical commercial aircraft, numerous windows are distributed along both sides of the fuselage from the rear of the cabin to just before the tail. The fuselage is tubular and varies in diameter or radius between the front and rear ends of the aircraft, and correspondingly the size and curvature of the windows also vary along the length of the aircraft.

Each window includes a frame properly mounted in a corresponding opening in the aircraft's outer casing, and each frame is securely mounted on a corresponding window glass.

Typical aircraft enclosures are made of highly resistant metal, such as aluminum, and the typical window frame is also made of highly resistant metal. Various methods of metal fabrication are then used to manufacture the individual window assemblies for different size and strength requirements, therefore depending on the specific location of the window along the length of the aircraft.

The weight of the aircraft directly affects the efficiency of the aircraft during flight, and the aircraft is then continuously being developed to reduce the weight while providing sufficient strength for various aircraft components to take advantage of long life during commercial operation.

In addition, the cost of operating the commercial aircraft is a major design objective, especially with the ever-increasing price of fuel. The initial manufacturing cost of the aircraft itself is also an important design objective, with both the acquisition cost of the initial aircraft and the subsequent operating cost being significant criteria in the competitive assessment of the aircraft and its expected low operating cost over its useful life. .

Consequently, it is desired to provide an optimized aircraft window frame, and method of its manufacture.

Summary of the Invention

An aircraft window frame includes a laminated outer edge and inner frame having a central opening for receiving window glass. The frame is transversely displaced from the edge and they include different layers between the opposite inner and outer sides of the frame.

Brief Description of Drawings

The invention, according to the preferred and exemplified modalities, together with additional objectives and advantages of these, is more particularly described in the following detailed description obtained in conjunction with the attached drawings, in which:

FIG. 1 illustrates a commercial aircraft exemplified in flight, with an enlarged cross-sectional view of the numerous windows found in it.

FIG. 2 is a profile view of the outer side of the exemplified window shown in FIG. 1 mounted on a part of the fuselage and obtained along line 2-2.

FIG. 3 is a partially cross-sectional isometric view of the exemplified window shown in FIG. 2 obtained in aircraft isolation.

FIG. 4 is an enlarged cross-sectional view of a part of the window shown in FIG. 3 and obtained along line 4-4.

FIG. 5 is a flowchart representation of the various layers forming the laminated window frame shown in FIGs. 3 and 4.

FIG. 6 is a flow chart of the multilayered sequence illustrated in FIG. 5 in the manufacture of the window frame.

FIG. 7 is a flow chart of the preparation and assembly of the layers illustrated in

FIG. 6.

FIG. 8 is a flow chart for pressing the stacked press load in FIG. 7 in the manufacture of the composite window frame.

Detailed Description of the Invention

FIG. 1 illustrates an exemplary plane or aircraft 10 powered by gas turboprop mechanisms in flight. The aircraft includes numerous windows 12 arranged in lines along both sides of the fuselage and the outer casing 14 from the front end of the aircraft cabin to just before the rear tail.

The windows maintain the cabin's pressure integrity and protect passengers from the outside environment, including the rapid flow of outside air 16 flowing behind the outside enclosure during the aircraft's flight.

Each window is suitably mounted through a corresponding opening in the aircraft enclosure 14, and the windows vary in size and configuration over the length of the aircraft. As the fuselage 14 is generally cylindrical or tubular, it has an internal diameter, or radius A, that varies along the length of the aircraft from the pointed nose, through the wide body of passengers, and up to the pointed tail.

Each window 12 is specifically sized and configured to achieve local curvature, or radius A, of the aircraft enclosure, and therefore many windows of different sizes are required for each aircraft, and need to be manufactured during production with corresponding differences.

The numerous windows on the aircraft may be identical in design, but may vary slightly in configuration, including their size and curvature. An exemplified window 12 is initially illustrated in the cross section in FIG. 1 and in plan view in FIG. 2. Each window includes a composite window frame 18 on which a conventional transparent window glass 20 is properly mounted. The frame 18 itself is suitably mounted through the corresponding opening in the housing of the aircraft 14 and supports its glass.

The composite table 18 is illustrated in more detail in an embodiment exemplified in FIGs. 3 and 4. The frame includes a radially external annular flange or rim 22 and a radially internal annular flange or frame 24 around a central opening 26 which is sealed by the window glass 20 mounted thereon.

The frame 24 is transversely displaced from the edge 22 through the thickness T of that in common laminations through that thickness. The laminated edge and frame include a plurality of sheets or layers, 1-7, for example, which extend laterally or radially through them along the radial axis R of the frame.

The blades or layers are preferably different from one another transversely between the opposite inner and outer sides 28, 30 of the frame corresponding to the inner side of the aircraft cabin and the outer side of the aircraft enclosure.

The frame 24 shown in FIG. 4 is raised above and transversely connected to the lower edge 22 by an annular rib 32 around the complete circumference of the central opening 26. The inner side of the frame 24 and the rib 32 define a central pocket 34 in which the window glass 20 can be mounted. The frame 24, or frame bar, defines an annular divider in which the window glass 20 can be mounted and secured, and withstands the differential pressure exerted through the window from the cabin of the pressurized aircraft.

The edge 22, frame 24, and rib 32 are integrated with each other into a single component or unitary component, and are continuous in circumference around the central opening 26 illustrated in FIGS. 2 and 3.

The integrated edge, frame, and rib then collectively define the front and rear vertical columns or posts 36, 38, and upper and lower horizontal rails 40, 42 integrally joined to their opposite ends.

The posts 36, 38 are spaced laterally or horizontally along the minor axis 44 of the frame 18, and define the horizontal width W of the frame.

The two rails 40, 42 are separated longitudinally or vertically along the longest axis 46 of the frame and define the height or length L thereof.

The two side posts 36, 38 laterally limit the central opening 26, and the two rails 40, 42 provide an upper beam and lower sill that vertically limit the central opening 26, and collectively, the posts and rails completely surround the central central opening 26 or circumferentially.

The edge 22 shown in FIGS. 3 and 4 have a thickness T preferably uni4 form from the outer perimeter of the frame its junction with the perpendicular rib 32 and provide sufficient surface area to structurally connect the window frame to the aircraft enclosure typically using screws or other suitable fasteners .

Correspondingly, the frame 24 narrows or decreases in thickness radially 5 inwardly from its junction with the rib 32 to the radially internal perimeter of the frame that defines a relatively thin arcuate edge 48 that circumferentially surrounds or limits the central opening 26.

In the preferred embodiment, the outer side 30 along the frame 24 is generally parallel to the inner side 28 along the edge 22 in two different planes generally 10 spaced transversely by the connecting rib 32.

Correspondingly, the inner side 28 of the frame 24 tilts radially outwardly towards the displaced lower edge 22 to its junction with the transition rib 32 to form an inclined annular seat 50 completely surrounding the window glass 20 which has a beveled perimeter corresponding with the seat chamfer.

In this way, the differential pressure loads acting on the window glass during the flight are carried through the hollow junction in the narrowed frame 24, frame 24 that has a relatively thick arcuate frame or junction with the transition rib 32 to, in turn, load the pressure loads on the surrounding edge with reduced tension.

The edge 22, the rib 32 and the frame 24 illustrated in FIG. 4 provide a continuous structural load path between the concentric outer and inner perimeters of the frame, and common layers 1-7 extend radially through it and comprise high-strength fibrous sheets fixedly attached to a rigid resin matrix 52 schematically illustrated in FIG . 4.

The different layers illustrated in FIG. 4 preferably include an externally exposed outer layer 1 facing the aircraft outwardly to the environment, an internally exposed inner layer 7 facing inward in the aircraft cabin, and a plurality of different inner or intermediate layers 2-6, for example, laminated and hidden between the opposite outer and inner layers.

The exposed common outer layer 1 completely covers the outer face of the window frame to provide impeccable window protection, including protection from lightning.

Additional protection for the window frame can be provided by attaching an annular erosion protection 54 to the outer side of the frame 24 as shown in FIGs. 2-4. The erosion protection is preferably thin metal foil, such as titanium, and provides a continuous metal annulus along posts 36, 38 and rails 40, 42 completely surrounding the central opening 26 to protect against wind and rain erosion.

The height or depth of the displacement between the frame 24 and the edge 2 shown in FIG. 4 is selected to achieve the enclosure thickness of the surrounding aircraft 14, shown in dashed lines, such that the outer surface of the frame is substantially flush with the outer surface of the aircraft enclosure.

Correspondingly, the thin erosion protection 54 is lowered into the frame and projects slightly outward from the aircraft casing by approximately 0.02 to 0.08 mm (1-3 mils) to provide a slightly raised relief to ensure that the protection against erosion stop the erosion of wind and rain instead of the window glass and the edge of the enclosure. The slight protrusion of the erosion protection, however, provides smooth aerodynamic flow of ambient air 16 as it flows past the window during aircraft operation at speed.

In addition, the erosion protection 54 illustrated in FIG. 4 fits the flat external surface of the frame and has opposite arcaded edges meeting internally in the aircraft. For example, the erosion protection 54 preferably coils in part around the rim of the frame 48 to minimize or eliminate direct exposure of the composite laminate underlying the flow of external free air 16 which may contain rain particles or debris that would otherwise way, they would erode the relatively softer composite frame.

The composite laminated window frame 18 shown in FIG. 3 takes advantage of specific advantages in design, strength, and manufacture, as well as in the cost of manufacture and durability of service life. The window frame 18 is defined by its common edge 22, frame 24, and transition rib 32 which can be suitably varied in size, thickness, and configuration with corresponding differences in length L, width W, and curvature in different planes represented by annular radius R of the window frame itself, as well as the vertical curvature A of the window frame adapting to the local curvature of the tubular aircraft cabin.

As window frame 18 is specifically configured for use on aircraft that can fly at substantial speed and elevation in a potentially hostile flight environment, it can be readily flawless in strength and attributes to improve its durability and structural performance. The laminated design of the window frame allows for virtually unlimited variations in material properties and configurations in the various layers introduced in the final frame design.

More specifically, the fibrous layers 1-7 illustrated in the cured state in FIG. 4 preferably include different annular patterns, designated by prefixes 56a-h, as shown schematically in FIG. 5, with the specific pattern for a specific layer being dependent on the final design of the window.

For example, for the exemplified aircraft illustrated in FIG. 1, seventeen different window configurations can be used for the substantially larger number of windows found on the aircraft, ninety-two, for example, recognizing the symmetry on opposite sides of the aircraft cabin. And, the seventeen configurations can also be differentiated by five basic weight classes for maximum resistance. These five weight classes include extra light, light, medium, heavy, and extra heavy in which rib 32 varies in height or length.

Consequently, the basic patterns 56a-h illustrated in FIG. 5 are examples of various standards that can be used in the manufacture of aircraft window frames depending on the specific application of the aircraft and the need for the windows. As the basic window frame itself is generally void, its configuration can be in the range of a round or circular window to the exemplified oval or oblong configuration illustrated in FIG. 2, and can extend to other configurations such as more rectangular or trapezoidal as desired for the specific aircraft application.

A particular advantage of the laminated window frame described above is the initially flat blade that can be readily cut into the common annular pattern illustrated in FIG. 5 and assembled together to complete the required frame configuration.

Although layer patterns can be continuous annulus, certain advantages result from the segmentation of each layer around its circumference. Consequently, each pattern 56a-h may include differently sized ribbon shapes or segments, designated by the suffix 1-4, with the segments being complementary to each other to collectively form the corresponding annular pattern 56a-h with proper overlap or separation of the segments around posts 36, 38 and rails 40, 42 shown in FIG. 3 surrounding the central opening 26.

As the basic configuration of the window frame shown in FIG. 3 is oblong in this embodiment, the corresponding patterns 56a-h shown schematically in FIG. 5 are correspondingly oblong and provide ribbon rings of fibrous material with small overlaps or junctions between adjacent segments in each layer.

As initially illustrated in FIG. 4, the outer layer 1 preferably has a different fibrous pattern than the inner layer, designated 7, for example. And, the intermediate layers 2-6, for example, preferably have different fibrous patterns than those of the outer layer 1 and the inner layer 7.

The various fibrous materials used in the window frame illustrated in FIG. 4 can be conventional and commercially available, and are preferably chosen for their different attributes. Representative fibrous materials are shown enlarged in FIGs. 4e5.

For example, the outer layer 1 preferably comprises a high-strength carbon fiber braided fabric with a flat weave having interwoven in this metal fibers or filaments, such as phosphorus, bronze or aluminum, to provide lightning protection for the window frame in your use on aircraft subject to storms. Filaments are schematically represented by the grid lines in FIG. 4, and the white squares represent the thin strands of fibers or bundles of non-spun fibers intertwined with these.

Suitable lightning fabric material is pre-impregnated with resin, such as epoxy resin, for subsequent curing, and is commercially available from Hexcel Corporation, Salt Lake City, Utah.

The intermediate layers 2-6 preferably comprise corresponding mats of randomly oriented pieces of carbon fiber or shavings to provide quasi-isotropic strength, or equal strength in all lateral directions in 360 degrees around the mats.

This high strength random fiber material is available under the brand name HexMC, or Hexcel Molding Compound, and is commercially available from Hexcel Corporation, Lyon, France. The chips are short strands of fiber or bundles of non-spun fibers pre-impregnated with epoxy or polymer resin, and are approximately 50.8 mm (2 inches) long and 8.5 mm (1/3 inch) wide, with a variable thickness of 50.8 by 8.4 by 0.1 to 0.2 mm (4-8 mils).

The inner layer 7 preferably comprises light fiberglass, or E-glass, fibers braided in thin fabric to prevent excessive leakage of carbon fiber from the underlying intermediate carbon layers when the edge is perforated to receive the fasteners for connection to the aircraft.

This fiberglass layer is commercially available in Style 108 from Hexcel Corporation, Salt Lake City, Utah.

All fibrous materials used in the numerous layers 1-7 of the window frame are supplied in woven fabrics or random mats in corresponding epoxy resin matrices, which upon final curing collectively form the unitary hard resin matrix 52 shown in FIG. 4 integrally connecting all the layers and all the fibers together in a single-part window frame.

The lightning strike outer layer 1 and the drilling mat inner layer 7 are located transversely between the numerous intermediate layers of high strength carbon 2-6 as required for the corresponding window configuration and strength.

Intermediate layers 2-6 can be as few or as numerous as desired, with all layers sharing the common quasi-tropic carbon fiber material found in these, but layers that are inherently different from each other due to the random orientation of the fiber shavings. carbon. However, the individual intermediate layers provide similar high strength in all directions, and numerous intermediate layers are used to correspondingly increase the strength and stiffness in the resulting window frame.

Since all layers 1-7 share the common oblong configuration of the resulting window frame, the various exemplified patterns 56a-h illustrated in FIG. 5 can be used as desired for the different fibrous layers.

For example, the outer lightning layer 1 illustrated in FIG. 4 preferably uses the 4-segment pattern 56g1-4 illustrated in FIG. 5 in order to maximize the use of material and minimize waste, and allow the bundle of non-spun fibers to be oriented more and less 45 degrees from the major and minor axes to avoid distortion during molding.

Correspondingly, the inner layer of drilling mat 7 shown in FIG. 4 preferably uses the two segment pattern 56h1,2 illustrated in FIG. 5 in order to maximize the use of the material and minimize waste.

And, the various intermediate layers 2-6 can use the various patterns 56a-f illustrated in FIG. 5. These various intermediate patterns include two or four segments around the perimeter of the window frame, with correspondingly small overlaps (shown as dashed lines) between them as required.

The different patterns allow circumferential displacement of the corresponding segment overlays, and can be used to control the final thickness of the window frame and maintain its uniformity within adequate tolerances.

In an exemplified embodiment, the five intermediate layers of high strength 2-6 shown in FIG. 4 correspond to the five different patterns 56a-e, respectively, shown in FIG. 5 to move or balance the joints of the corresponding joints as far as possible.

As the cross-sectional profile of the window frame shown in FIG. 4 varies from the outer edge of uniform thickness 22 to the inner frame of narrowed thickness 24, the various patterns and material compositions illustrated in FIG. 5 can be used to precisely control both the thickness profile and the edge and frame offset configuration.

In the seventeen different configurations of the aircraft window frames, the various edge and frame dimensions illustrated in FIG. 4 vary, and can be readily accommodated by varying the different patterns 56a-h illustrated in FIG. 5 as required to better form the specific frame design in uniformity of composition and relatively free from irregularities and defects.

The thickness, length, local width, and profile of each flat pattern can be selected such that when the multiple layers are combined in a pile, they collectively form the required three-dimensional (3D) profile shown in FIG. 4. This includes the edge of plane 22, perpendicular rib 32, and displaced narrow frame 24.

For example, since the window frame is formed of numerous layers of fibrous materials initially in the flat form, these flat layers need to be properly shaped in the 3D configuration illustrated in FIG. 4, which includes the relatively sharp curvature between the flat edge 22 and the perpendicular rib 32, with the frame 24 again curving, in turn, generally perpendicular to the vertical rib 32.

The initial flexibility inherent in the raw pre-impregnated intermediate layers 26 and the outer and inner layers 1,7 allows preparation and premolding, and then molding the previously flat layers with flexible shear or lateral displacement between the layers to achieve the final 3D window frame profile. without undesirable wrinkling of the layers or undesirable spaces in them.

In particular, the random non-woven mat shape of the fibers in the intermediate layers 2-6 provides additional advantages in achieving complex 3D shapes. The individual fiber shavings in the mat layers can shift and flow in their resin matrices both laterally in each layer and transversely between the adjacent layers during the preparation and molding process to achieve the variant thickness and 3D cross profiles in the final composite frame without undesirable defects.

As indicated above, the various patterns 56a-h illustrated in FIG. 5 share common attributes since they use substantially full-width tape segments collectively mounted on each layer to achieve the oblong pattern of the final window frame.

For example, patterns 56a, c, e, g, h include corresponding single vertical segments on the corresponding front and rear posts 36, 38. Correspondingly, patterns 56b, c, d, e, g include single segments on the corresponding top and bottom rails 40, 42. In this way, the corresponding joints can be located at the transition corners between the posts and rails.

The first two patterns 56a, b and pattern 56h illustrated in FIG. 5 include double segments, or two only, which collectively form both posts 36, 38 and rails 40, 42 with two joints only. Double segments 56a, h are continuous on posts 36, 38 and overlap together on side rails 40, 42. Correspondingly, double segments 56b are continuous on rails 40, 42 and overlap together on posts 36,38.

In this way, the overlapping joints can be confined either on the posts or on the rails close to the axes of neutral curvature corresponding to the major and minor axes 4, 46, and depends on the specific configuration of the window frame.

Patterns 56c, d, e, g are each four segments only that collectively form posts 36, 38 and rails 40, 42 on each layer. In these configurations, the posts and rails can have substantially continuous fibrous material, with the overlapping joints being located close to the four corners that connect the posts to the rails.

In these patterns, two segments form the two posts 36, 38 and two segments form the two tracks 40, 42.

In the two patterns 56e, g, the four segments overlap on the rails 40, 42. And in the two patterns 56c, the four segments overlap on the two posts 36, 38.

Since the window frame shown in FIG. 2 is oblong along the major axis 46, the central opening 26 shown in FIGs. 2 and 5 is similarly oblong, with the window approaching a generally rectangular configuration with four arched corners.

Correspondingly, the pattern 56f includes two pairs of rectangular segments 56f1,2 and 56f3,4 that can be arranged symmetrically around the minor or major axis 44, 46 or both, and as described here below can be used to take advantage to control the final weight of the window frame while symmetrically adding to the desired frame strength around the two axes of curvature 44, 46.

In view of the oblong configuration of the exemplified window, the two patterns 56a, b include a pair of semi-long segments that can also be arranged symmetrically around the major and minor axes 44, 46 for structural advantage. In these configurations, the joints are located on the corresponding neutral curvature axes 44, 46 in which the curvature stress is minimal.

The laminated configuration composed of the window frame illustrated in FIG. 4 includes the differently configured outer layer 1 and inner layer 7, and one or more intermediate layers 2-6.

In practice, the individual layers are relatively thin and then multiple intermediate layers 2-6 will be used to increase thickness and strength. And, the multiple exemplified patterns illustrated in FIG. 5 allow various exchanges of the layer configuration to specifically join each window frame to its intended location on the aircraft, as well as specifically configuring the cross section illustrated in FIG. 4 to mount the window glass 20 on it, and, in turn, mounting the window frame to the aircraft.

The composite design of the window frame then takes advantage of design efficiencies, impeccable strength, and ease of fabrication that complements the laminate configuration itself.

FIGs. 5 to 8 schematically illustrate a method of manufacturing or making the composite laminated window frame 18 in a preferred embodiment.

As indicated above, the initial fibrous materials can be commercially sought in a typical cylindrical or flat shape. In particular, the fibrous material is supplied in pre-impregnated fibrous sheets of resin, designated 1-7p to correspond with their layered form. The uncured pre-impregnated blades are suitably cut flat in shape or profile in the various desired patterns 56a-h illustrated in FIG. 5 to form the correspondents of the outer, inner, and intermediate layers 1-7 shown cured in FIG. 4.

In FIG. 6, the various pre-impregnated layers 1-7 are still soft in their raw, uncured state, and can be readily assembled into such a common pile in a sequence of preferred layers.

Depending on the total number of layers required, one or two stacks of the pre-impregnated layers can be assembled, with two stacks 1-4 and 5-6 being illustrated schematically.

In FIG. 7, the stack or pre-impregnated cells 1-4 and 5-6 are suitably prepared, or prepared in B, under heat in an oven 58 to partially search for the resin matrix. This preparation controls the viscosity of the resin and the relative flexibility of the pile, and allows the initially stacked layers to suit each other.

The stack thus prepared is then cooled to form a ready-to-press load 60.

In FIG. 8, the press load 60 undergoes molding in a two-part mold 62, 64 under suitable heat and pressure to form the cured laminated window frame 18 and 3D contour.

Due to the random configuration of the intermediate layers of carbon chips 2-6, the weight tolerance in the corresponding pre-impregnated material of these is relatively high, and around twenty percent (+/- 20%), for example. This means for a unit area of ​​the intermediate layers, the weight of which can vary at most another 20 percent or less 20 percent which is particularly problematic since the reference or specification weight for the final window frame needs to be closely kept in place. small tolerances of about one percent, for example.

However, the large variation in weight of the intermediate pre-impregnated layers corresponds to the substantial flexibility of these crude layers and their variable thickness. These attributes are used to take advantage of precisely forming the final frame without wrinkles and unwanted spaces.

Consequently, each pre-impregnated layer 1-7 is suitably weighed before pressing the layers, and for layers 1-6 this weighing is preferably carried out without the adhering film conventionally provided in the pre-impregnations, while weighing in the inner layer 7 can be conducted with its cling film in view of its extremely flexible shape. The weight of the cling film can be explained separately and removed (by taring) from the final weight.

After the layers are weighed, their collective weight can then be compared with the corresponding design or reference specification weight for the final frame. If the design weight is not achieved, the collective weight of the stacked pre-impregnated layers 1-7 can be adjusted by adding additional pre-impregnated layers to the stack or removing pre-impregnated layers in order to achieve the specification weight within the desired small tolerance.

The adjustment weight should be added to or removed from the pre-impregnated stack symmetrically with respect to either the minor or major axis 44, 46, or both. For example, a complete layer (8^The), such as the two-segment pattern 56b shown in FIG. 5 can be added to the stack where a large weight gain is required.

Or, the rectangular strip pattern 56f shown in FIG. 5 can be added in pairs at the pole or rail positions, or both as required in a different layer (9^The).

Correspondingly, excess weight can be removed by removing an entire layer, or symmetrically removing parts of a single layer.

In this way, the final weight of the window frame can be precisely controlled within small weight tolerances by controlling the number of intermediate layers and patterns of these for the high strength random fiber mats that are placed between the differently configured inner and outer layers 1 , 7.

In order to control the effectiveness of the preparation process, the number of intermediate layers 2-6 in an individual stack together with the outer lightning layer 1 is limited, to a maximum of five, for example. If more than five intermediate layers are required, then the layers should be divided substantially equally into two corresponding stacks for preparation.

For example, for six intermediate layers, three layers each would be supplied in two stacks, with one stack including the lightning layer 1.

For seven intermediate layers, three intermediate layers would be stacked with the lightning layer in one stack, and four intermediate layers would be mounted in another stack.

In FIG. 6, five intermediate layers 2-6 are illustrated, with three intermediate layers 2-4 being assembled in a stack with the lightning layer 1, and the other stack including the two intermediate layers 5,6.

For the preparation of two stacks of the fibrous layers illustrated in FIG. 6, the collective weight of the two stacks is preferably adjusted by adding or removing the pre-impregnated layers on top of one or both of the two stacks.

As shown in FIG. 7, the two pre-impregnated cells 1-4 and 5-6 are separately prepared side by side, for example, in oven 58 and partially heated cured.

Following proper cooling of the prepared piles, the two piles can be stacked together in a complete stack 1-6 to form the common press charge 60 which then undergoes molding as described above.

As shown schematically in FIGs. 6 and 7, the pre-impregnated layers are preferably stacked in numerical sequence or positioned in a stack 1-4 starting first with the pre-impregnated outer layer 1 and followed by the corresponding ones of intermediate layers 2-4, for example. And in the other stack, the remaining intermediate layers 5-6 are stacked in numerical or reverse sequence. The stacking sequence is determined by the position of the requirement layer in the specific frame design.

In this way, pre-impregnated stacks 1-4 and 5-6 can then be stacked end to end as illustrated in FIG. 7 to provide a continuous numerical or positional sequence between the inner and outer sides 28, 30 for the resulting window frame 18.

That reverse sequence of the intermediate structural layers 2-6 in the two stacks shown in FIGs. 6 and 7 allows the adjustment of the collective weight of the layers close to the middle of the pile. This adjustment maintains the structural integrity of the layers that limit the central layer of the frame close to the axis of neutral curvature, and maximizes the structural strength resulting from the frame.

Furthermore, since the preferred sequence and patterns of the intermediate layers are used to control the different sizes and configurations of the numerous windows, the adjustment of the weight of the frames along the central layer will not adversely affect the final configuration of the frame.

Since the initial pre-impregnated layers 1-7 shown in FIG. 6 are formed from pre-impregnated initially flat material, and the final configuration of the molded window frame 18 shown in FIG. 8 varies in 3D configuration, further optimization in the manufacturing method can be achieved by introducing tools or trays 66, 68 illustrated schematically in FIGs. 6 and 7.

The pre-impregnated layers 1-4 are preferably stacked on top of a first preparation tray 66, with the remaining intermediate pre-impregnated layers 5,6 being correspondingly stacked on top of a second preparation tray 68. The two trays 66, 68 are similar in 3D size and configuration with the corresponding external and internal sides 28, 30 of the resulting window frame 18.

For example, FIG. 3 illustrates the outer side 30 of the window frame 18 in which the annular frame 24 is raised on a plateau above the surrounding lower edge 22. Consequently, the first preparation tray 66 shown in FIG. 6 will be similar in mirror image configuration with the outer side 30 shown in FIG. 3, and includes a central molding recess or surface corresponding to the raised frame, and a raised molding surface or edge corresponding to the edge of the window.

As the window frame shown in FIG. 3 has a slight curvature A along its longitudinal axis, the inner side 28 is slightly concave in the vertical direction around the aircraft, and the opposite outer side 30 is slightly convex. Correspondingly, the top of the first tray 66 shown in FIG. 6 will be slightly concave to fit the slightly convex outer side 30 of the window frame.

Similarly, the second tray 68 shown in FIG. 6 fits the inner side 28 of the window frame shown in FIG. 3. The top face of the second tray 68 will then be slightly convex to fit the slightly concave inner side 28 of the window frame. The second tray 28 has an elevated molding frame or internal surface conforming to the recessed seat 50 of the frame 54 shown in FIG. 4, with a surrounding molding edge or bottom surface matching the inner surface of the frame edge 22.

Consequently, the corresponding pre-impregnated stacks 1-4 and 5-6 can then be prepared on top of their corresponding trays 66, 68 as shown schematically in FIG. 7 which will suit the initially flat prepregs 1-6 to the 3D configuration of the corresponding frame sides 28, 30. The preformed prepared layers 1-6 would no longer be flat and would initially better match the desired final configuration of the window frame 18 shown in FIG . 8, and thus improve the pressing of the preformed press load 60.

The initial pre-impregnated material includes flexible fibers and an uncured resin matrix that maintains the flexibility of the cut pre-impregnated layers. The stacked pre-impregnated layers remain flexible, but nevertheless have increased stiffness due to their relatively thick assembly.

During heat preparation, the elevated temperature of oven 58 affects the viscosity of the resin which may become lower or more liquid due to heating, but with continued heating, the prepared layers become more rigid due to partial curing. Consequently, the preparation is preferably conducted to obtain a press load 60 with suitable resin viscosity and layer flexibility such that during subsequent pressing, the layer press load stack will more readily conform to the desired 3D frame configuration window.

In the preferred embodiment illustrated in FIG. 7, only outer layer 1 and intermediate layers 2-6 are prepared under heat and then adequately cooled. The two piles are assembled together in a common pile after which the inner pre-impregnated layer 7 is then added to the pile prepared to form the final press charge 60 before pressing it. The two trays 66, 68 are suitably removed from both stacks to form the press load 60 which is sufficiently rigid for manual handling and for seating inside the lower press mold 62 for the subsequent pressing operation.

As indicated above, pressing can be performed using the pair of molds 62, 64 shown in FIG. 8 which are specifically configured for the corresponding inner and outer sides 28, 30 of the resulting window frame 18. The lower mold 62 includes a complementary annular recess in it that matches the inner side 28 of the frame

18. And, the upper mold 64 has a complementary fixed stop adapting to the external side 30 of the frame.

The preformed press load 60 is located in the lower mold 62 and then covered with the upper mold 64, and then substantial pressure is applied to it to mold the press load under heat to cure the resin matrix therein and form the window frame. hard 18.

In a truly conducted manufacturing process, the pre-impregnated stacks 1-4 and 5-6 illustrated in FIG. 7 were prepared in several hundred degrees for a part of an hour for proper preparation of that and pre-molding on the support trays 66, 68. The resulting pre-press load 60 was then pressure-molded in the pair of molds 62, 64 shown in FIG . 8 and a suitably higher cure temperature for less than an hour under a high molding pressure exceeding 1000 psi. The pressures, temperatures, and actual times for preparation and molding will be determined for the specific material and resin compositions desired according to conventional practice.

In this way, the initially flat pre-impregnated layers 1-6 were prepared in a complementary intermediate preform and then pressure molded into the final configuration in which the various layers were able to smoothly and regularly slide in relation to each other to achieve the 3D graded configuration of the window frame without unpleasant wrinkling of layers or unwanted spaces or other defects in these.

Such defects can be properly detected in the final window frame 18 using various forms of non-destructive testing, such as ultrasonic detection, to optimize the quality control of the resulting window frames 18.

Following the operation and pressing illustrated in FIG. 8, the window frame 18 can undergo suitable post-processing. For example, the window frame can be sanded using suitable sandpaper to remove sharp edges and foreign material. The window frame can also be cured at elevated temperature long enough to complete curing and harden the specific resin matrix, such as typical heat cured epoxy resins.

And, a line of holes properly drilled around the perimeter of the frame edge 22 to receive fasteners for later connection of the frame to the aircraft fuselage. The inner perforation mat layer 7 prevents excessive carbon leakage from the intermediate layers when the edge is perforated from its outer side.

As part of the postprocessing of the window frame 18, the metal guard 5 against erosion 54 can be suitably attached to the outer side of the frame 24 to protect the frame and its inner rim from rain and particle erosion when used in aircraft application.

In final form, the composite laminated window frame 18 is a unitary part of a part being relatively simple in configuration with the outer supporting edge 22 and the narrow displaced inner frame 24. The window frame takes advantage of the substantial strength of its laminated construction with high strength carbon fibers and is substantially rigid due to its simple 3D configuration.

The preferred manufacturing process described above allows the pre-impregnated initially flat layers to conform to each other and to slide as required as the flat layers are prepared and shaped in the final 3D configuration of the frame. Wrinkles and unwanted spaces or defects in the layers and their integral resin matrix are avoided or reduced to maximize the yield of acceptable window frames being manufactured.

While it has been described here that they are considered to be preferential and exemplified embodiments of the present invention, other modifications of the invention should be apparent to those skilled in the art from the teachings cited herein, and therefore it is desired to protect in the appended claims all such modifications to the as they are within the spirit and true scope of the invention.