COMPOSITE LAMINATE AND A METHOD OF MANUFACTURING A COMPOSITE LAMINATE

Abstract

A method of manufacturing a composite laminate. The method comprises providing a base layer, providing a discontinuous reinforcing patch on the base layer, and providing a top layer over the base layer and discontinuous reinforcing patch. Also, a composite laminate having a discontinuous reinforcing patch interposed between a base layer and a top layer. The discontinuous reinforcing patch comprises a patterned nanomaterial layer with nanomaterial-filled zones and vacant zones.

Claims

1. A method of manufacturing a composite laminate, the method comprising the steps of: providing a base layer formed from polymeric material; providing a discontinuous reinforcing patch on the base layer, the discontinuous reinforcing patch comprising a patterned nanomaterial layer having at least one nanomaterial-filled zone and at least one vacant zone; and providing a top layer formed of polymeric material over the base layer and discontinuous reinforcing patch such that the discontinuous reinforcing patch is interposed between the base layer and the top layer, wherein the method further comprises: providing a continuous reinforcing patch; and processing the continuous reinforcing patch to form the discontinuous reinforcing patch.

2. The method of claim 1, wherein the continuous reinforcing patch is provided and processed to form the discontinuous reinforcing patch prior to providing the discontinuous reinforcing patch on the base layer.

3. The method of claim 1, wherein the continuous reinforcing patch is provided and processed on the base layer to form the discontinuous reinforcing patch in situ on the base layer.

4. The method of claim 3, further comprising the steps of: providing a masking film on the base layer, the masking film including a discontinuous cut-out; pressing the continuous reinforcing patch on the masking film, wherein nanomaterials in the continuous reinforcing patch transfer through the discontinuous cut-out and onto the base layer; and removing the masking film to leave the discontinuous reinforcing patch on the base layer.

5. The method of claim 3, wherein the masking film is formed from fluorinated ethylene propylene release film.

6. The method of claim 1, wherein the processing of the continuous reinforcing patch comprises etching or ablation to form the vacant zones.

7. The method of claim 1, further comprising: providing the discontinuous reinforcing patch with a plurality of discrete nanomaterial-filled zones surrounded by an interconnecting vacant zone; or providing the discontinuous reinforcing patch with a plurality of discrete vacant zones surrounded by an interconnecting nanomaterial-filled zone.

8. A method of manufacturing a composite laminate, the method comprising the steps of: providing a base layer formed from polymeric material; providing a discontinuous reinforcing patch on the base layer, the discontinuous reinforcing patch comprising a patterned nanomaterial layer having at least one nanomaterial-filled zone and at least one vacant zone; and providing a top layer formed of polymeric material over the base layer and discontinuous reinforcing patch such that the discontinuous reinforcing patch is interposed between the base layer and the top layer; wherein the method further comprises: growing the discontinuous reinforcing patch on a substrate, wherein the discontinuous reinforcing patch is provided on the base layer by transferring the discontinuous reinforcing patch from the substrate to the base layer.

9. The method of claim 8, wherein the substrate comprises a discontinuous catalyst coating thereon for promoting the growth of the nanomaterial-filled zones.

10. The method of claim 8, further comprising: providing the discontinuous reinforcing patch with a plurality of discrete nanomaterial-filled zones surrounded by an interconnecting vacant zone; or providing the discontinuous reinforcing patch with a plurality of discrete vacant zones surrounded by an interconnecting nanomaterial-filled zone.

11. A composite laminate comprising: a base layer and a top layer formed from polymeric material; and a discontinuous reinforcing patch interposed between the base layer and the top layer, wherein the discontinuous reinforcing patch comprises a patterned nanomaterial layer having at least one nanomaterial-filled zone and at least one vacant zone.

12. The composite laminate of claim 11, wherein nanomaterials in the at least one nanomaterial-filled zone are vertically aligned carbon nanotubes.

13. The composite laminate of claim 12, wherein carbon nanotubes in the at least one nanomaterial-filled zone have an average length between and including 5 μm to 60 μm.

14. The composite laminate of claim 11, wherein the discontinuous reinforcing patch comprises a plurality of discrete nanomaterial-filled zones surrounded by an interconnecting vacant zone.

15. The composite laminate of claim 11, wherein the discontinuous reinforcing patch comprises a plurality of discrete vacant zones surrounded by an interconnecting nanomaterial-filled zone.

16. The composite laminate of claim 11, wherein the at least one nanomaterial-filled zone and/or the at least one vacant zone has an irregular shape.

17. The composite laminate of claim 11, wherein the at least one nanomaterial-filled zone and the at least one vacant zone are arranged according to an irregular pattern.

18. The composite laminate of claim 11, wherein the discontinuous reinforcing patch further comprises a polymer film.

19. The composite laminate of claim 11, formed as a gas turbine engine component.

Description

DESCRIPTION OF THE DRAWINGS

[0049] Embodiments will now be described by way of example only, with reference to the Figures, in which:

[0050] FIG. 1 is a microscope image of a fractured composite laminate without a continuous CNT interlayer, the image showing predominantly interlaminar fracture behaviour;

[0051] FIG. 2 is an electron microscope image of a fractured composite laminate with a continuous CNT interlayer, the image showing predominantly intralaminar fracture behaviour;

[0052] FIG. 3 is a top perspective view of a partly formed composite laminate according to the present disclosure;

[0053] FIG. 4A shows a diagram of vertically aligned carbon nanotubes;

[0054] FIG. 4B shows a diagram of vertically aligned carbon nanotubes that have buckled;

[0055] FIG. 5A is a top perspective view of a partly formed composite laminate with a discontinuous reinforcing patch comprising a chequered pattern;

[0056] FIG. 5B is a top perspective view of a partly formed composite laminate with a discontinuous reinforcing patch comprising a chevron pattern;

[0057] FIG. 6 is a flow chart of a method of manufacturing a composite laminate according to the present disclosure;

[0058] FIG. 7 is a top perspective view of a continuous reinforcing patch that is used in an embodiment of the present disclosure; and

[0059] FIGS. 8A-8D shows photographs of the method steps for manufacturing a composite laminate according to the present disclosure. The steps including: providing a masking film with a discontinuous cut-out (FIG. 8A), providing a masking film on a base layer (FIG. 8B), providing a continuous reinforcing patch on the base layer (FIG. 8C), and pressing the continuous reinforcing patch on the masking film and base layer (FIG. 8D).

DETAILED DESCRIPTION

[0060] Aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

[0061] FIG. 3 illustrates a composite laminate 300 comprising a base layer 302 formed from a polymeric material, specifically HexTow® IM7/HexPly® 8552 prepreg carbon fibre reinforced polymer. The laminate 300 includes a discontinuous reinforcing patch 304 on the surface of the base layer 302. The discontinuous reinforcing patch 304 covers a rectangular area on the surface of the base layer (delimited by the dashed lines). The discontinuous reinforcing patch 304 comprises a patterned nanomaterial interlayer that includes nanomaterial-filled zones 306 and a vacant zone 308. In practice, a polymeric top layer (not shown) is provided over the base layer 302 and discontinuous reinforcing patch 304 so that the discontinuous reinforcing patch 304 interposes the base layer 302 and top layer. The discontinuous reinforcing patch 304 therefore provides interlaminar reinforcement for the base layer 302 and top layer when present.

[0062] The nanomaterial-filled zones 306 are occupied by nanomaterials, specifically, carbon nanotubes (CNTs), which are aligned in a vertical direction to bridge the interlaminar region between the base layer 302 and top layer. The CNTs in the nanomaterial-filled zones 306 therefore form a nanoforest that connects the base layer 302 and top layer when assembled.

[0063] A diagrammatic representation of vertically aligned CNTs 400 is illustrated in FIG. 4A. In the illustrated embodiment each CNT 401 has a generally circular transverse cross-section 402 that extends in a longitudinal direction to form a tubular shape (in other embodiments the cross-section 402 may be elliptical). Each CNT 401 has a central axis 404, a first end 406 and a second end 408. The central axis is defined by the centroid of all the transverse cross-sections 402 of the CNT. Within the nanomaterial-filled zones 306, the CNTs are aligned such that the central axis 404 of each CNT 401 is approximately parallel with the other CNTs in the nanomaterial-filled zone 306. The direction of the alignment (i.e. the vertical direction, V) corresponds to a direction perpendicular to the planar base layer 302 and top layer. In other words, the central axes 404 of the CNTs are approximately perpendicular to the surface of the base layer 302.

[0064] Each CNT 401 has an actual length, L′ and a chord length, L″. The actual length, L′ is the length of the CNT 401 taken along the central axis 404. The chord length is the length of a straight line extending between opposite (i.e. longitudinal) ends of the CNT 401. For a linear CNT 401, the actual length, L′ and the chord length, L″ will be the same (see FIG. 4A). For a curved CNT 451 (as shown in FIG. 4B), the actual length, L′ will be larger than the chord length, L″. For example, in some instances vertically aligned CNTs can buckle during fabrication of the composite laminate. A diagrammatic representation of vertically aligned ‘buckled’ CNTs 450 is shown in FIG. 4B. While CNT buckling effectively shortens the chord length, L″ of the CNTs in the vertical direction, V by adding curvature to the central axis 454, the actual length, L′ of the CNT is unaffected. The average (‘actual’) length, L′ of the CNTs in the nanomaterial-filled zones 306 is therefore independent of any CNT buckling behaviour. The average (‘actual’) length, L′ of the CNTs in the nanomaterial-filled zones 306 is between 11 μm to 15 μm.

[0065] Turning back to FIG. 3, the vacant zone 308 consists of areas of the discontinuous reinforcing patch 302 that are substantially free from CNTs. Accordingly, at the vacant zone 308, the base layer 302 and top layer are joined by bonding of their constituent polymeric materials only.

[0066] The nanomaterial-filled zones 306 of the reinforcing patch 304 are arranged to form discrete islands of vertically aligned CNTs that are surrounded by an interconnecting vacant zone 308. The nanomaterial-filled zones 306 each have an irregular shape (i.e. the edges of each zone have different lengths and the corners of each zone corners have different internal angles) and are quasi-randomly distributed within the area occupied by the reinforcing patch 304.

[0067] Alternatively, the nanomaterial-filled zones 306 can be distributed in a uniform arrangement/pattern within the area occupied by the reinforcing patch 304. Examples of uniformly distributed nanomaterial-filled zones are shown in FIG. 5A (i.e. a laminate 500 with a chequerboard pattern 502) and FIG. 5B (i.e. a laminate 550 with a chevron pattern 552). The chequerboard pattern 502 consists of square nanomaterial-filled zones 506 and square vacant zones 508 that alternate in a direction across the length, y of the reinforcing patch, and also in a direction across the width, x of the reinforcing patch. The chevron pattern 552 consists of nanomaterial-filled zones 556 in the shape of zig-zags that extend along the entire length, y of the reinforcing patch. Each chevron nanomaterial-filled zone 556 is separated by a chevron vacant zone 556 with a similar zig-zag shape such that the nanomaterial-filled zone 556 and vacant zone 558 alternates across the width of the reinforcing patch, x. Accordingly, in both instances (chequerboard and chevron) the nanomaterial-filled zones 506/556 repeat periodically along a direction on the surface of the base layer 302.

[0068] An exemplary method 600 of manufacturing the composite laminate of the present disclosure will now be described. The method is shown as a flow chart in FIG. 6.

[0069] In a first step 602 of the method 600, a base layer 302 formed of a polymeric material (in the present case, HexTow® IM7/HexPly® 8552 prepreg) is provided.

[0070] In the second step 604, a continuous reinforcing patch is provided. FIG. 7 shows an example of a continuous reinforcing patch 700. The patch 700 consists of uniformly arranged CNTs 702 that are vertically aligned. The CNTs are growth onto a substrate 704 using a conventional CNT growth method, e.g. combustion chemical vapour deposition. In the context of the continuous reinforcing patch, the term “vertically aligned” relates to the CNTs having longitudinal axes that extend approximately perpendicular to the surface of the substrate 704.

[0071] In the third step 606, a masking film 802 is provided on the base layer 302. The masking film 802 is formed from fluorinated ethylene propylene (FEP) release film and includes a discontinuous cut-out 804. The cut-out 804 is produced by adhering the masking film 802 to a cutting board 806 and programming a CNC machine 808 to cut a discontinuous cut-out shape from the masking film 802 (see FIG. 8A). The discontinuous cut-out 804 may be a uniform, random, or quasi-random pattern. Once the masking film 802 is cut by the CNC machine 808 to form the discontinuous cut-out 804, the masking film 802 is arranged on the surface of the base layer 302 at a location where interlaminar reinforcement is required (see FIG. 8B).

[0072] In the fourth step 608, the continuous reinforcing patch 700 is pressed onto the masking film 802, specifically, at the location of the discontinuous cut-out 804. In order to minimise any lateral movement of the continuous reinforcing patch 702 during pressing, the continuous reinforcing patch 702 is secured to the masking film 802 and base layer 302 through applying adhesive tape 810 across the substrate 704 from which the continuous reinforcing patch 700 is provided (see FIG. 8C). The base layer 302, masking film 802 and continuous reinforcing patch 700 are then fed through a heated roller 812 (at a temperature of approximately 68° C. and feed rate of 600 mm/min) to transfer CNTs from the substrate 704 and on to the base layer 302 (see FIG. 8D). By pressing the continuous reinforcing patch 700 against the masking film 802, CNTs located at/over the removed sections of the masking film 802 (i.e. the discontinuous cut-out 804) are able to pass through the masking film 802 and on to the surface of the base layer 302, where they adhere to the tacky surface of the polymeric material of the base layer 302. On the other hand, CNTs located away from the discontinuous cut-out 804 are blocked from making contact with the base layer 302 and so are inhibited from transferring on to the base layer 302.

[0073] In the fifth step 610, the masking film 802 (and the substrate 704) are removed from the base layer 302. Since only the CNTs located at the discontinuous cut-out 804 of the masking film 802 deposit and remain on the surface of the base layer 302, a discontinuous (patterned) reinforcing patch 304 is now provided on the surface of the base layer 302. Examples of different discontinuous reinforcing patches 304 on the base layer 302 are shown in FIGS. 3 and 5.

[0074] In a sixth step 612, a top layer (not shown) formed of a polymeric material (in this case, another layer of HexTow® IM7/HexPly® 8552 prepreg) is provided over the base layer 302 and discontinuous reinforcing patch 304. Resultantly, the discontinuous reinforcing patch 304 interposes the base layer 302 and top layer, or in other words, the discontinuous reinforcing patch 304 forms and interlayer between the base layer 302 and top layer.

[0075] To minimise the possibility of trapped air between the base layer 302 and top layer, the laminate 300 can be debulked under vacuum for at least 10 minutes. The laminate is then be room cured, oven cured, or autoclave cured. The type of cure selected will depend on the polymeric material of the base layer 302 and top layer, and the desired mechanical properties of the laminate 300.

[0076] It will be understood that this disclosure is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.