Method of forming a perforated composite panel

Abstract

A perforated composite panel comprises a substrate and an applied layer, the substrate having a first surface and an opposite second surface. A method of forming the perforated composite panel comprises the steps of: i. cutting a plurality of first holes in the substrate; ii. positioning the applied layer against the substrate such that a surface of the applied layer overlays the first surface of the substrate to thereby form the composite panel; iii. locating the composite panel in a fixture, the fixture having one or more datum features; iv. determining the location and axis direction for each of the first holes in the substrate, relative to the or each datum feature; and v. cutting a plurality of second holes in the applied layer, each of the plurality of second holes being coincident and coaxial with a corresponding one of the plurality of first holes.

Claims

1. A method of producing a perforated composite panel, the composite panel comprising a substrate and an applied layer, the substrate having a first surface and an opposite second surface, the method comprising the steps of: i. cutting a plurality of first holes in the substrate; ii. positioning the applied layer against the substrate such that a surface of the applied layer overlays the first surface of the substrate to thereby form the composite panel; iii. locating one or more datum features on the composite panel; iv. determining the location and axis direction for each of the first holes in the substrate, relative to the or each datum feature; and v. cutting a plurality of second holes in the applied layer, each of the plurality of second holes being coincident and coaxial with a corresponding one of the plurality of first holes.

2. The method as claimed in claim 1, wherein step ii. comprises the additional subsequent step of: ii. adhesively bonding the surface of the applied layer to the first surface of the substrate.

3. The method as claimed in claim 1, wherein step i. comprises the additional initial step of: i. forming the substrate into a predetermined shape.

4. The method as claimed in claim 1, wherein step i. comprises the additional subsequent step of: i. forming the substrate into a predetermined shape.

5. The method as claimed in claim 1, wherein the substrate is formed from a first material and the applied layer is formed from a second material, a hardness of the first material being greater than a corresponding hardness of the second material.

6. The method as claimed in claim 1, wherein the axis of each of the first holes is inclined at an acute angle to the normal to the plane of the substrate.

7. The method as claimed in claim 1, wherein the diameter of each of the plurality of second holes is smaller than the diameter of the corresponding one of the plurality of first holes.

8. The method as claimed in claim 1, wherein each of the plurality of second holes is cut from the second surface of the substrate.

9. The method as claimed in claim 1, wherein two or more of the first holes are cut simultaneously.

10. The method as claimed in claim 1, wherein two or more of the second holes are cut simultaneously.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There now follows a description of an embodiment of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which:

(2) FIG. 1 shows a schematic sectional view of a perforated composite panel formed by the method of the present invention;

(3) FIG. 2 shows a schematic flow diagram illustrating the method of the present invention; and

(4) FIG. 3 shows a schematic sectional view of one arrangement of the step of forming a hole through the panel.

(5) It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

(6) Referring to FIG. 1, a perforated composite panel formed by an embodiment of the invention is designated generally by the reference numeral 100.

(7) The perforated composite panel 100 comprises a substrate 110 and an applied layer 120. The substrate 110 has a first surface 112 and an opposite second surface 114. The applied layer 120 extends over and covers the first surface 112 of the substrate 110.

(8) The perforated composite panel 100 forms a liner panel 100 for the exhaust system (not shown) of a gas turbine engine (also not shown). The gas turbine engine is installed in an aircraft (also not shown) but may equally be installed in another form of transport (also not shown) or even in a stationary installation (also not shown) such as, for example, an electrical power generating installation (also not shown).

(9) In the embodiment shown the substrate 110 is formed as a titanium alloy sheet. Alternatively the substrate 110 may be formed from another metal or metal alloy sheet material. In a further alternative the substrate 110 may be formed from a fibre reinforced composite material such as, for example, a carbon fibre reinforced sheet material.

(10) The applied layer 120 is attached to the first surface 112 of the substrate 110 by an adhesive compound. Alternatively the applied layer 120 may be attached to the substrate by an alternative fastening technique such as, for example, with rivets or screws.

(11) In the method of the invention a plurality of first holes 130 are formed in the substrate 110. In the method as shown in FIG. 2 the plurality of first holes 130 are formed in the substrate 110 while the substrate 110 is still in its unformed sheet form. Each of the plurality of first holes 130 is formed such that the axis 132 of each first hole 130 is oriented at an acute angle 134 to the normal 118 to the plane 116 of the substrate 110.

(12) In one embodiment of the invention, each of the plurality of first holes 130 is formed at an angle of 70 to the plane 116 of the substrate 110. In other embodiments of the invention, each of the plurality of first holes 130 may be formed at another angle 134 to the normal 118 to the plane 116 of the substrate 110.

(13) The perforated substrate 110 is then formed by any suitable forming technique into a pre-determined three dimensional geometrical form.

(14) In an alternative embodiment of the method of the invention, the substrate 110 may first be formed into the pre-determined three dimensional geometrical form and then subsequently perforated with the plurality of first holes 130.

(15) The step of perforating the substrate 110 with the plurality of first holes 130 may be achieved using any conventional hole forming technique such as, for example, laser forming, electrical discharge machining or mechanical cutting.

(16) At this stage, one or more supports may be attached to the second surface 114 of the substrate 110. In the embodiment shown, the support(s) serve to attach the perforated composite panel 100 to the internal surface (not shown) of the exhaust system.

(17) The assembled composite panel 100 is then located in a fixture (not shown) which enables one or more datum features 150 to be defined on the first surface 112 of the composite panel 100.

(18) The first surface 112 of the composite panel 100 is then scanned in order to identify the positions, and orientation of the corresponding axis, of each of the first holes 130 relative to the or each datum feature 150. In the method of the invention this scanning process is performed by an ultrasound scanning machine. Alternatively another scanning technique may be employed to positionally locate the plurality of first holes 130.

(19) Once the position and orientation of each of the plurality of first holes 130 has been determined then a plurality of second holes 160 may be cut into the applied layer 120 with each of the second holes 160 corresponding to a respective one of the first holes 130. Each of the second holes 160 is cut so as to be concentric with and coaxial with a corresponding one of the first holes 130.

(20) Once the position of each of the first holes 130 has been established each of the second holes 160 can be drilled from either side of the composite panel 100 to produce an aligned combination of corresponding first and second holes 130,160.

(21) In practice it is likely that each of the second holes 160 is drilled from direction of the second surface 114 of the substrate 110 to minimise the effect of tolerances and scanning error.

(22) Since the applied layer 120 is made from an easily machined material then very small diameter holes can be drilled so a high aspect ratio holes can be produced (aspect ratio being defined as the ratio of the hole's diameter to its length). In other words a high aspect ratio drill is one that is long and thin. Holes below diameters of 0.6 mm could be generated.

(23) Multi head drilling machines could be used to increase manufacturing time. To maximise accuracy the scanning and drilling could be done in stages or small areas at a time with the scanner on the machine or drill head.

(24) In practice the drill used to form each of the second holes 160 may be a little smaller than the diameter of the first hole 130 in the substrate 110 in order to prevent the drill from catching on the sides of the first hole 130 in the substrate 110, which may cause drill damage.

(25) The differences in first hole 130 and second hole 160 diameters will need to accommodate, for example, the effect of positional tolerances and drill wear. Where drill damage does not take place then the drill will be arranged to drill each second hole 160 as near to the first hole 130 in the substrate 110 as practically possible.

(26) FIG. 3 shows the drill passing through a first hole 130 in the substrate 110. Especially if the drill was a hand held then the substrate 110 could be used as a guide for the drill bit. To avoid the drill breaking in bending then a flexible drive member, such as a small diameter rubber tube or proprietary coupling could be placed between the drill and drill bit.

(27) The foregoing description of various aspects of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person of skill in the art are included within the scope of the invention as defined by the accompanying claims.