EP4727745A1

EP4727745A1 - Procedure for processing a dry carbon fiber fabric laminate

Info

Publication number: EP4727745A1
Application number: EP24727847.6A
Authority: EP
Inventors: Giorgio Paolini
Original assignee: Paolini SpA
Current assignee: Paolini SpA
Priority date: 2023-06-16
Filing date: 2024-04-18
Publication date: 2026-04-22
Also published as: IT202300012444A1; WO2024257131A1

Abstract

The present invention relates to a process for processing a laminate of a dry carbon fibre fabric, said dry carbon fibre fabric comprising an upper surface and a lower surface, said process comprising the following steps: (a1) overturning said dry carbon fibre fabric by turning said upper surface downwards; (a2) positioning said overturned carbon fibre fabric on an absorbent panel comprising an upper face so that said upper surface of said overturned carbon fibre fabric is in contact with the upper face of said absorbent panel; (b1) applying at least one layer of a polyurethane resin compound and of a polyurethane diluent on said lower surface of said overturned carbon fibre fabric to obtain an impregnated overturned carbon fibre fabric; (c1 ) positioning said absorbent panel and said impregnated overturned carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50% and for at least 12 hours, (d1 ) separating the absorbent panel from said impregnated overturned carbon fibre fabric, overturning said impregnated carbon fibre fabric by turning the lower surface downwards and positioning said carbon fibre fabric on said absorbent panel so that said lower surface is in contact with the upper face of said absorbent panel; (e1) positioning said absorbent panel and said impregnated carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50% and for at least 48 hours, (fO) separating the absorbent panel from said impregnated carbon fibre fabric, (f1) positioning a cloth having open cells on the upper surface of said impregnated carbon fibre fabric, (f2) applying a layer of a resin on said cloth; (f3) removing said cloth from said upper surface of said impregnated carbon fibre fabric; (g1) positioning said impregnated carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50% and for at least 24 hours for the completion of catalysis; (e) carrying out a finishing of the surface.

Description

PROCESS FOR PROCESSING A LAMINATE OF A DRY CARBON FIBRE FABRIC

The present invention relates to a process for processing a laminate of a dry carbon fibre fabric.

In particular, the present invention relates to a process for processing a laminate of a dry carbon fibre fabric aimed at obtaining a final product that preserves the aesthetic characteristics typical of carbon fibre in the natural dry state.

As is well known, the carbon fibre laminates present on the market are produced with different designs and weights through conventional lamination of carbon fibre, starting from a dry fibre or a pre-impregnated fibre. In particular, the current carbon fibre laminates are normally covered by a layer of epoxy resin or the like, used in lamination processes.

In fact, carbon fibres are presently used for performance purposes, with vacuum, autoclave, mechanical pressing, or atmosphere techniques that have the objective of removing the air present in the dry carbon fibre, which would impart fragility to the final product. Therefore, the conventional techniques provide for pressing the dry carbon fibre during the lamination phase with the use of epoxy resins and the complete removal of air, while leaving the right amount of epoxy resin in the fibre as necessary to impart to the final product the physical characteristics necessary for the required use.

Furthermore, the lamination can take place using a vacuum pump, autoclave, mechanical press, or atmosphere, respecting thermo-hygrometric parameters and process specifications that ensure catalysis of the resin. Use is further made of a detaching fabric called peel ply, with the aim of making the excess resin flow onto an outer layer that will later be removed. These steps can also take place with preimpregnated carbon fibres.

In dry fibres, the application of the resin takes place in various ways, including by infusion, manual application, or spray application and in other ways.

The aesthetic component that is obtained from such processes is thus the characteristic one of such processing cycles. This means that the thicknesses normally obtained with conventional lamination are considerably smaller than those of the starting carbon fibre.

By way of example, if one measured the thickness of a sheet of dry carbon fibre and then the measurement was repeated after lamination, a considerable decrease in the latter would be found.

Furthermore, in laminates, and more in particular in the laminated carbon fibre fabrics known to date, the pore, i.e. the physical interstice between the carbon braids, as well as the space existing between filament and filament of the carbon braid, is closed as a result of pressing of the fibre and filling with resin. The upper surface as well is normally covered by a layer (albeit thin) of epoxy resin used in lamination processes.

Therefore, upon a touch with the hand, one does not perceive the native morphology of the dry carbon fibres, but rather the smooth surface of the resin, as the spaces and air the fibre presents in the warp are filled with resin and are no longer perceptible to the touch.

The aesthetic effect between the dry fibre and the final post-lamination fibre is also different, since the carbon fibre can be seen only through the transparency of the lamination resin.

In conclusion, the current processing of dry carbon fibre produces a final product with a matt or glossy epoxy resin surface, beneath which the carbon fibre is trapped.

Thus, in the specific sector there exists a need for a process for processing dry carbon fibre which is able to safeguard the aesthetic characteristics of dry carbon fibre, such as the reflection of light and/or three-dimensionality of the warp.

This need is satisfied by the process according to the present invention, which offers, moreover, further advantages that will become clear below.

The solution according to the present invention fits into this context; it proposes to abandon all the stereotypes typical of the specialist world in order to develop a new carbon philosophy called “Carbon Touch” (CT), which places safeguarding the starting aesthetic characteristics of dry carbon fibre at the centre of attention.

In particular, the process according to the present invention allows for preserving the aesthetic characteristics carbon fibre has when it is dry, i.e. not yet impregnated. In particular, the aesthetic variation between the product obtained through the process of the present invention and the raw dry fibre is less than 5%, versus the over 80% attributed to conventional processed carbon products.

Moreover, the process according to the present invention allows for preserving over 90% of the spaces present between filament and filament of the carbon braid and in the physical interstice between carbon braids, i.e. in the openpore warp, whereas in traditional carbon fibre this value is lower than 5%. This makes it possible to preserve the three-dimensionality typical of dry carbon fibre, since air is also present in the interstices at the end of the processing process according to the present invention.

In particular, the presence of air in the product obtained through the process according to the present invention stands at a value ranging between 80% and 88%, whereas in conventional laminated carbon it is between 0% and 5%.

Furthermore, through the process according to the present invention one obtains a product with a final thickness reduction with values lower than 20% compared to dry carbon fibre, whereas in the products obtained by means of the processes of the prior art it is greater than 50%.

The aim of the present invention is thus to provide a process for processing a dry carbon fibre that makes it possible to overcome the limits of the processes according to the prior art and to obtain the previously described technical results.

A further aim of the invention is that said process can be implemented with substantially low costs, both as regards production costs and as far as management costs are concerned.

Yet another aim of the invention is to propose a process that is simple, safe, and reliable.

Therefore, a specific object of the present invention is a process for processing a laminate of a dry carbon fibre fabric, said dry carbon fibre fabric comprising an upper surface and a lower surface, said process comprising the following steps:

(a1 ) overturning said dry carbon fibre fabric by turning said upper surface downwards;

(a2) positioning said overturned carbon fibre fabric on an absorbent panel comprising an upper face so that said upper surface of said overturned carbon fibre fabric is in contact with the upper face of said absorbent panel;

(b1 ) applying at least one layer of a polyurethane resin compound and a polyurethane diluent on said lower surface of said overturned carbon fibre fabric until reaching a slight impregnation in order to obtain an impregnated overturned carbon fibre fabric, in particular said at least one layer being applied by spreading with a spatula; (c1 ) positioning said absorbent panel and said impregnated overturned carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50% and for at least 12 hours, (c2) extracting said absorbent panel and said impregnated overturned carbon fibre fabric from said closed chamber,

(d1 ) separating the absorbent panel from said impregnated overturned carbon fibre fabric, overturning said impregnated carbon fibre fabric by turning the lower surface downwards and positioning said carbon fibre fabric on said absorbent panel so that said lower surface is in contact with the upper face of said absorbent panel,

(d1 .1 ) performing a visual inspection to detect any oozing of resin onto the upper surface of said impregnated overturned carbon fibre fabric,

(e1 ) positioning said absorbent panel and said impregnated carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50% and for at least 48 hours for the completion of catalysis,

(e1.1 ) extracting said absorbent panel and said impregnated carbon fibre fabric from said closed chamber,

(fO) separating the absorbent panel from said impregnated carbon fibre fabric,

(f1 ) positioning a cloth having open cells on the upper surface of said impregnated carbon fibre fabric,

(f2) applying a layer of a resin on said cloth by means of a brush, exerting slight pressure to enable the compound to completely wet the carbon fibre fabric; the low viscosity of the resin allows the impregnated carbon fibre fabric to return to its basic morphology after the compression stress of the brush for impregnation; the air that is within the carbon fibre remains trapped, for a value comprised between 80% and 88% compared to the initial state;

(f3) removing said cloth from said upper surface of said impregnated carbon fibre fabric, thus also removing the excess resin not necessary for the impregnation step;

(g1 ) positioning said impregnated carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50%, and for at least 24 hours for the completion of catalysis;

(e) carrying out a surface finishing.

According to the invention, said at least one layer of a polyurethane resin compound and of a polyurethane diluent of said step (b1 ) has a thickness comprised between 10 pm and 100 pm.

In particular, said step (f1 ) of positioning a cloth having open cells on the upper surface of said impregnated carbon fibre fabric can be preceded by the following sub-step:

(f12) positioning said impregnated carbon fibre fabric on an absorbent panel comprising an upper face so that said lower surface is in contact with the upper face of said absorbent panel.

In addition, said cloth having open cells can be a cloth made of nonwoven material or a nylon film, or else a peel ply fabric. In particular, said cloth allows the passage of the resin and prevents the release of fibres.

According to the invention, said step (a2) of positioning said overturned carbon fibre fabric on an absorbent panel can be preceded by the following substep:

(aO) preparing an absorbent panel comprising a first layer of a peel ply fabric, a second layer of an absorbent felt, and a third anti-adhesion layer; this panel has the aim of absorbing all the excess blocking resin that should arrive on the upper surface of the carbon fibre fabric.

Moreover, according to the invention, said second layer of an absorbent felt can have thickness comprised between 1 mm and 2 mm.

According to the invention, said third anti-adhesion layer can be made of nylon or PVC.

Moreover, according to the invention, said step (b1 ) of applying at least one layer of a polyurethane resin compound and of a polyurethane diluent can comprise the following sub-step:

(bO) mixing the 40% of a polyurethane resin with the 60% of a polyurethane diluent for at least 3 minutes and at most 5 minutes. In particular, the polyurethane resin is preferably a Berner 407648 polyurethane resin and the polyurethane diluent is an ICA UNI 1263 D1010-9200 polyurethane diluent. Furthermore, the compound must be mixed for 3-5 minutes until total blending of the two parts, i.e. until obtaining the right density given by the dilution ratio expressed above.

Again according to the invention, in said step (f2) of applying a layer of a resin, said resin can comprise between 18% and 21 % of ICA OAC 363G2 acrylic resin, between 1 .5% and 2.5% of ICA C200 catalyst, and between 75% and 85% of ICA UNI 1263 D1010-9200 polyurethane diluent. In particular said resin comprises 19.6% of ICA OAC 363G2 acrylic resin, 1.9% of ICA C200 catalyst, and 78.5% of ICA UNI 1263 D1010-9200 polyurethane diluent.

In particular, according to the invention, said process can further comprise the following step, after said step (d1 ) and/or said step (g1 ):

(d2) removing the oozes of compound from the upper surface of said carbon fibre.

According to the invention, said step (d2) of removing the oozes can be carried out by wiping a cloth made of nonwoven fabric soaked with a polyurethane diluent over said upper surface of the carbon fibre. In particular, a slight pressure is exerted in order not to alter the surface of the carbon fibre that is not yet “blocked”. The operation is repeated until the exposed face is totally cleaned. In particular, said step is repeated on all the areas of the carbon fibre fabric where one should detect an excess of resin compared to all the other parts. The inspection is visual, and is carried out by the operator.

More in particular, according to the invention, said surface finishing step (e) can comprise the following sub-step:

(e1 ) carrying out an abrasion by sanding with a sandpaper.

According to the invention, said abrasion by sanding can be carried out with a sandpaper on the X+Y axis relative to the carbon fibre, preferably by hand.

In particular, according to the invention, said abrasion by sanding can be carried out with a series of G1000 + G2000 sandpapers.

According to the invention, said surface finishing step (e) can comprise the following sub-step:

(e2) applying a layer of the compound of step (f2) having a thickness comprised between 5 pm and 7 pm.

Again according to the invention, said step (e2) can be carried out by means of an airbrush having a 0.5 mm nozzle and pressure of 2 bar. Gloss parameters of 0 to 100 can also be selected by changing the specifications of the OAC 363G20 resin for this coating step. The present invention has been described by way of non-limiting illustration according to preferred embodiments thereof, but it is to be understood that variations and/or modifications can be introduced by the person skilled in the art without going outside the relevant scope of protection, as defined by the appended claims.

Claims

1 ) A process for processing a laminate of a dry carbon fibre fabric, said dry carbon fibre fabric comprising an upper surface and a lower surface, said process comprising the following steps:

(b1 ) applying at least one layer of a polyurethane resin compound and of a polyurethane diluent on said lower surface of said overturned carbon fibre fabric to obtain an impregnated overturned carbon fibre fabric;

(c1 ) positioning said absorbent panel and said impregnated overturned carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50% and for at least 12 hours,

(d1 ) separating the absorbent panel from said impregnated overturned carbon fibre fabric, overturning said impregnated carbon fibre fabric by turning the lower surface downwards and positioning said carbon fibre fabric on said absorbent panel so that said lower surface is in contact with the upper face of said absorbent panel;

(e1 ) positioning said absorbent panel and said impregnated carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50% and for at least 48 hours,

(fO) separating the absorbent panel from said impregnated carbon fibre fabric,

(f2) applying a layer of a resin on said cloth;

(f3) removing said cloth from said upper surface of said impregnated carbon fibre fabric;

(g1 ) positioning said impregnated carbon fibre fabric in a closed chamber at a temperature comprised between 3°C and 50°C, preferably comprised between 8°C and 25°C, even more preferably comprised between 8°C and 14°C, humidity less than 50% and for at least 24 hours for the completion of catalysis;

(e) carrying out a finishing of the surface.

2) The process according to the preceding claim, characterised in that said step (f1 ) of positioning a cloth having open cells on the upper surface of said impregnated carbon fibre fabric, is preceded by the following sub-step:

3) The process according to any one of the preceding claims, characterised in that said at least one layer of a polyurethane resin compound and of a polyurethane diluent of said step (b1 ) has a thickness comprised between 10 pm and 100 pm.

4) The process according to any one of the preceding claims, characterised in that said step (a2) of positioning said overturned carbon fibre fabric on an absorbent panel is preceded by the following sub-step:

(aO) preparing an absorbent panel comprising a first layer of a peel ply fabric, a second layer of an absorbent felt, and a third anti-adhesion layer.

5) The process according to the preceding claim, characterised in that said second layer of an absorbent felt has a thickness comprised between 1 mm and 2mm.

6) The process according to claim 4 or 5, characterised in that said third antiadhesion layer is made of nylon or PVC.

7) The process according to any one of the preceding claims, characterised in that said step (b1 ) of applying at least one layer of a polyurethane resin compound and of a polyurethane diluent comprises the following sub-step:

(bO) mixing the 40% of a polyurethane resin with the 60% of a polyurethane diluent for at least 3 minutes and at most 5 minutes.

8) The process according to any one of the preceding claims, characterised in that in said step (f2) of applying a layer of a resin, said resin comprises between 18% and 21 % of ICA OAC 363G2 acrylic resin, between 1.5% and 2.5% of ICA C200 catalyst, and between 75% and 85% of ICA UNI 1263 D1010-9200 polyurethane diluent.

9) The process according to any one of the preceding claims, characterised in that it further comprises the following step, after said step (d1 ) and/or said step (g1 ):

10) The process according to the preceding claim, characterised in that said step (d2) of removing the oozes is carried out by wiping a cloth made of nonwoven fabric soaked with a polyurethane diluent over said upper surface of the carbon fibre.

11 ) The process according to any one of the preceding claims, characterised in that said surface finishing step (e) comprises the following sub-step:

(e1 ) carrying out an abrasion by sanding with a sandpaper.

12) The process according to the preceding claim, characterised in that said abrasion by sanding is carried out with a sandpaper on the X+Y axis relative to the carbon fibre.

13) The process according to claim 11 or 12, characterised in that said abrasion by sanding is carried out with a series of G1000 + G2000 sandpapers.

14) The process according to any one of the preceding claims, characterised in that said surface finishing step (e) comprises the following sub-step:

15) The process according to the preceding claim, characterised in that said step (e2) is carried out by means of an airbrush having a 0.5 mm nozzle and pressure of 2 bar.