EP4727744A1

EP4727744A1 - Procedure for processing a laminate of a pre-impregnated carbon fiber fabric

Info

Publication number: EP4727744A1
Application number: EP24727001.0A
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: WO2024257132A1; IT202300012450A1

Abstract

The present invention relates to a process for processing a laminate of a carbon fibre fabric pre-impregnated with a resin, in particular an epoxy resin, said pre¬ impregnated carbon fibre fabric comprising an upper surface and a lower surface, said process comprising the following steps: (a1 ) positioning said pre-impregnated carbon fibre fabric on an absorbent panel comprising an upper face, so that said lower surface of said pre-impregnated carbon fibre fabric is in contact with the upper face of said absorbent panel; (b1 ) positioning said absorbent panel and said pre-impregnated carbon fibre fabric in a closed chamber at a temperature higher than the catalysis activation temperature of said resin, humidity less than 50% and for at least 20 minutes, (c1 ) carrying out a cleaning of the upper surface of said pre-impregnated carbon fibre fabric, (d1 ) positioning said absorbent panel and said pre-impregnated carbon fibre fabric in a closed chamber at a temperature higher than the catalysis activation temperature of said resin, humidity less than 50% and for at least 4 hours, (e) carrying out a surface finishing.

Description

PROCESS FOR PROCESSING A LAMINATE OF A PRE-IMPREGNATED CARBON

FIBRE FABRIC

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

In particular, the present invention relates to a process for processing a laminate of a pre-impregnated 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. For example, carbon fibre laminates can be covered by an epoxy, vinyl ester or phenolic resin.

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 pre-impregnated carbon fibre, which would impart fragility to the final product. Therefore, the conventional techniques provide for pressing the pre-impregnated carbon fibre during the lamination phase, 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. In particular, the epoxy resins present in pre-impregnated carbon fibres are temperature activated.

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.

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.

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 resin, i.e. a lamination residue.

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.

In conclusion, the current processing of pre-impregnated 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 pre-impregnated carbon fibre which is able to safeguard the aesthetic characteristics of the 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 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.

Moreover, the process according to the present invention allows for preserving the spaces present between filament and filament of the carbon braid and in the physical interstice between carbon braids, i.e. in the open-pore warp.

Furthermore, through the process according to the present invention one obtains a product with a final thickness reduction of between 20% and 30% compared to pre-impregnated 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 pre-impregnated 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, an object of the present invention is a process for processing a laminate of a carbon fibre fabric pre-impregnated with a resin, preferably an epoxy resin or a vinyl ester or phenolic resin, said pre-impregnated carbon fibre fabric comprising an upper surface and a lower surface, said process comprising the following steps:

(a1 ) positioning said pre-impregnated carbon fibre fabric on an absorbent panel comprising an upper face so that said lower surface of said pre-impregnated carbon fibre fabric is in contact with the upper face of said absorbent panel;

(b1 ) positioning said absorbent panel and said pre-impregnated carbon fibre fabric in a closed chamber at a temperature higher than the catalysis activation temperature of said resin, humidity less than 50% and for at least 20 minutes,

(c1 ) carrying out a cleaning of the upper surface of said fabric of carbon fibre,

(d1 ) positioning said absorbent panel and said pre-impregnated carbon fibre fabric in a closed chamber at a temperature higher than the catalysis activation temperature of said resin, humidity less than 50% and for at least 4 hours,

(e) carrying out a surface finishing.

Furthermore, after said step (b1 ) an inspection can be performed to verify that the resin of the pre-impregnated carbon fibre is in a liquid state and drains towards the absorbent panel.

According to the invention, said step (a1 ) of positioning said pre-impregnated 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. In particular, this panel has the aim of absorbing all the excess resin present in the pre-impregnated carbon fibre fabric that is not necessary for the process. Moreover, according to the invention, said second layer of an absorbent felt can have thickness comprised between 1 mm and 2 mm.

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

More in particular, according to the invention, said step (c1 ) of carrying out a cleaning of the upper surface of said pre-impregnated carbon fibre fabric 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, the polyurethane diluent can be an ICA UNI 1263 D1010-9200 diluent.

Again 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.

Moreover, 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.

Furthermore, 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 resin having a thickness comprised between 5 pm and 7 pm.

In particular, according to the invention 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.

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.

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

CLAIMS 1 ) A process for processing a laminate of a carbon fibre fabric preimpregnated with a resin, in particular an epoxy resin, said pre-impregnated carbon fibre fabric comprising an upper surface and a lower surface, said process comprising the following steps: (a1 ) positioning said pre-impregnated carbon fibre fabric on an absorbent panel comprising an upper face, so that said lower surface of said pre-impregnated carbon fibre fabric is in contact with the upper face of said absorbent panel; (b1 ) positioning said absorbent panel and said pre-impregnated carbon fibre fabric in a closed chamber at a temperature higher than the catalysis activation temperature of said resin, humidity less than 50% and for at least 20 minutes, (c1 ) carrying out a cleaning of the upper surface of said pre-impregnated carbon fibre fabric, (d1 ) positioning said absorbent panel and said pre-impregnated carbon fibre fabric in a closed chamber at a temperature higher than the catalysis activation temperature of said resin, humidity less than 50% and for at least 4 hours, (e) carrying out a surface finishing. 2) The process according to the preceding claim, characterised in that said step (a1 ) of positioning said pre-impregnated 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. 3) 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 2 mm. 4) The process according to one of claims 2 or 3, characterised in that said third anti-adhesion layer is made of nylon or PVC. 5) The process according to any one of the preceding claims, characterised in that said step (c1 ) of carrying out a cleaning of the upper surface of said preimpregnated carbon fibre fabric is carried out by wiping a cloth made of nonwoven fabric soaked with a polyurethane diluent over said upper surface of the carbon fibre. 6) 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. 7) 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.

8) The process according to claim 6 or 7, characterised in that said abrasion by sanding is carried out with a series of G1000 + G2000 sandpapers.

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

(e2) applying a layer of resin having a thickness comprised between 5 pm and 7 pm. 10) The process according to the preceding claim, characterised in that 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.

11 ) The process according to one of claims 9-10, 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.