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GB2546962A - Apparatus and method of impregnating reinforcement material - Google Patents

Apparatus and method of impregnating reinforcement material Download PDF

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Publication number
GB2546962A
GB2546962A GB1522516.2A GB201522516A GB2546962A GB 2546962 A GB2546962 A GB 2546962A GB 201522516 A GB201522516 A GB 201522516A GB 2546962 A GB2546962 A GB 2546962A
Authority
GB
United Kingdom
Prior art keywords
resin
prepreg
reinforcement
belt
deposit surface
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB1522516.2A
Other versions
GB201522516D0 (en
Inventor
Arcidiacono Marco
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hexcel Composites Ltd
Original Assignee
Hexcel Composites Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hexcel Composites Ltd filed Critical Hexcel Composites Ltd
Priority to GB1522516.2A priority Critical patent/GB2546962A/en
Publication of GB201522516D0 publication Critical patent/GB201522516D0/en
Publication of GB2546962A publication Critical patent/GB2546962A/en
Withdrawn legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29BPREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B15/00Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00
    • B29B15/08Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00 of reinforcements or fillers
    • B29B15/10Coating or impregnating independently of the moulding or shaping step
    • B29B15/12Coating or impregnating independently of the moulding or shaping step of reinforcements of indefinite length
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28Shaping operations therefor
    • B29C70/40Shaping or impregnating by compression not applied
    • B29C70/50Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
    • B29C70/504Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC] using rollers or pressure bands
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29BPREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B11/00Making preforms
    • B29B11/14Making preforms characterised by structure or composition
    • B29B11/16Making preforms characterised by structure or composition comprising fillers or reinforcement
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28Shaping operations therefor
    • B29C70/40Shaping or impregnating by compression not applied
    • B29C70/50Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
    • B29C70/504Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC] using rollers or pressure bands
    • B29C70/506Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC] using rollers or pressure bands and impregnating by melting a solid material, e.g. sheet, powder, fibres

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Reinforced Plastic Materials (AREA)

Abstract

A method for impregnation of fibrous material with a resin comprises the steps of, depositing a film of thermoplastic resin onto the outer surface of a first continuous surface such as belt 200 or a cylindrical surface and bringing a layer of fibrous reinforcement 206 into contact with the resin. The reinforcement and resin is pressed between the first surface and a second surface such as belt 202, and removed from between the first and second surfaces. The method may produce a prepreg or cured laminate with a high degree of impregnation without using a backing sheet, for use in automotive or wind-energy applications. The resin and reinforcement may be heated prior to and during compression by heaters 209, 208 and may be cooled by cooling plates 210 prior to removal from the belts. A protective sheet 211 may be applied to prepreg prior to winding onto a drum 212. The belts may comprise PTFE.

Description

APPARATUS AND METHOD OF IMPREGNATING REINFORCEMENT MATERIAL
FIELD OF THE INVENTION
The present invention relates to a method of impregnating fibrous material with a resin, particularly but not exclusively to a method of impregnating a fibrous reinforcement material to form a composite moulding material such as a prepreg.
BACKGROUND
Composite materials comprise a fibrous reinforcement embedded within a matrix material. These materials are laid up in a mould and cured to form a rigid part. Typically the matrix material is formed from a thermoset resin that is cured by polymerising it into a rigid lattice of cross-linked polymer chains. In order to ensure the resin is applied in the optimum quantity and to completely wet out the fibres, it is preferred to preimpregnate the fibrous reinforcement before it is applied to the mould. A preimpregnated fibrous reinforcement is known as a prepreg. Incomplete impregnation of the fibrous material results in an increase of voids in the final cured part, thus it is desirable to use prepregs as they achieve a high degree of resin impregnation.
Prepregs with a high degree of resin impregnation are typically formed by first casting resin as a thin film onto a backing sheet. The resin coated faces of the backing sheets (101, 102 of Figure 1) are then brought into contact with a fibrous reinforcement material (103). Usually two resin films are simultaneously brought into contact with the fibrous reinforcement on opposing faces. Rollers are used either in nip (104) or s-wrap configuration to apply pressure to the backs of the backing sheets to drive the resin into the fibrous reinforcement to completely impregnate the fibres with resin. Once the resin has been pressed into the fibrous reinforcement the backing sheets are removed (105, 106), and if necessary more resin added by applying subsequent resin films (107, 108) in the same manner. Once the prepreg has been fully impregnated any remaining backing sheets are removed (109, 110) and replaced with a polymeric protective (111) sheet to prevent the prepreg from sticking to itself as it is wound onto a roll (112).
The backing sheets act as barriers between the apparatus and the resin to prevent fouling and accumulation of resin on the impregnation apparatus. This is particularly important when using thermoset resins such as epoxy resins used in structural composites, as their nature means they are particularly tacky.
The backing paper also provides a convenient moving surface on which to cast the resin films. The backing sheet is usually a silicone coated paper which functions as a releasable carrier medium for the resin; the silicone coating provides a low surface energy surface which can be peeled away from the tacky thermosetting resin film. For every meter of prepreg that is produced two or four meters of backing sheet are required, this represents a significant proportion of prepreg production costs as well as an environmental cost. The silicone of the backing sheet is also a contaminant to the resin which can interfere with the cure reaction, degrading the mechanical properties of the final cured part.
There is therefore a need in the art to achieve impregnation of a prepreg having a high degree of resin impregnation and reduced variance of resin content. For prepreg production to be economically viable appropriate production rates need to be achieved.
The invention aims to obviate and/or mitigate the above described problems and/or to provide improvements generally.
SUMMARY OF THE INVENTION
According to the invention there is provided an apparatus and a method as defined in any one of the accompanying claims.
In an embodiment of the present invention the deposit member is positioned above the contact member and resin is first deposited onto the upwards facing face of the deposit member. This provides increased area over which the resin and fibres can be heated before coming into contact with the contact member. This arrangement also means the apparatus occupies a smaller area.
According to a preferred aspect of the invention the contact member comprises a further deposit member.
In an embodiment of the present invention the fibrous reinforcement comprises glass fibre or carbon fibre. The fibrous reinforcement in may be in any suitable form for use in structural composites, examples include but are not limited to a unidirectional fabric, a woven fabric or a stitched grid fabric.
In an embodiment of the invention resin conditioning is performed on the resin and/or reinforcement material. Resin conditioning means may comprise an infrared lamp and/or heated plate. Alternative methods of heating can also be applied, for example by use of a sonotrode.
In an aspect of the present invention there is provided a method for impregnation of fibrous material with a resin, without the use of a backing sheet comprising the steps of: depositing a resin directly onto the outer surface of a first continuous belt; bringing a layer of fabric into contact with the resin on the first belt; heating and pressing the fabric and resin between the first belt and a second belt to form a prepreg from the fibre and the resin, and; cooling the prepreg then removing it from between the first and second belt.
Because the resin is deposited onto the first belt, resin accumulation on the second belt is minimised. Resin accumulated on the first belt is also of negligible consequence because the belt is continuous, so the accumulated resin is incorporated into a new layer of film that is deposited on top. Thus the method can operate without the apparatus becoming fouled with tacky resin.
By filming resin onto the first belt, the same process and apparatus that is used for filming onto a conventional backing sheet can also be used. This means a film with a low variance of resin distribution can be produced, which results in a prepreg with a low variance of resin content. Pressing between two belts provides an elongated area over which impregnation occurs, increasing the extent of impregnation.
By heating the resin prior to or upon its deposit, its viscosity is reduced so that the pressure needed to drive the resin into the fibrous reinforcement is reduced, ensuring a high degree of impregnation. Because the method uses belts rather than rollers, there is an elongated area over which heat can be applied. This means the resin can be in a heating zone for longer so that the line speed is not inhibited by needing the resin to move through a small heating zone slowly. By cooling the prepreg before removing it from the belts the tack of the resin is reduced which minimises the amount of resin left on the belt.
In an embodiment of the present invention the resin and fibrous reinforcement are heated before contacting the second belt. This increases the area over which heat is applied before it is pushed into the resin allowing line speeds to be increased. By heating the fibrous reinforcement before it contacts the resin and this also improves the impregnation of the resin into the tows of the fibrous reinforcement.
In an embodiment of the present invention the thermosetting resin comprises an epoxy resin. The present invention is suitable for impregnating fibrous reinforcements with epoxy resins to achieve prepregs with a high degree of impregnation suitable for high strength applications.
In an embodiment of the present invention the belts comprise a PTFE surface to minimise adhesion between the resin and the belt. Other low surface energy coatings may also be used such as silicone or silane.
In an embodiment of the present invention the heating zone of first belt is greater than two metres long. This provides enough area to heat the resin to a suitable viscosity for achieving a high degree of impregnation with line speeds of up to 20 m/minute.
In an embodiment of the present invention the prepreg is cured as it is removed from between the belts. This produces a rigid laminate which can be used in automotive or wind energy applications. By curing the laminate online the present invention provides a method for producing a low cost laminate with a high degree of resin impregnation.
In an embodiment of the resent invention the belts can be cleaned of any accumulated resin by passing a flexible sheet of material between them. Preferably the material comprises a thermoplastic fabric which is particularly suited for collecting resin. This provides a rapid and straightforward way of cleaning the belts, thus minimising equipment downtime. This also eliminates the need for scraping the belts which damages their surface.
The Water Pickup Test is used to determine the degree or extent of impregnation of a prepreg. Values as low as 0.4% can be achieved using the method of the present invention. In this test, a specimen of prepreg material 40 mm by 10 mm is initially weighed (wl) and clamped between two plates in such a way that a strip 5 mm wide protrudes. This arrangement is suspended in the direction of the fibres in a water bath at room temperature (21°C) for 5 minutes. The specimen is then removed from the plates and excess water is removed from the surface and weighed again (w2) and the difference in weight provides a value for the degree of impregnation within the specimen. The smaller the amount of water picked up, the higher the degree of waterproofing or impregnation. WPU (water pick up, %) = (w2 — wl)/wl x 100.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be explained by way of example only by and with reference to the following Figures in which:
Figure 1 is a diagrammatic example of a nip process of impregnation of the prior art, and; Figure 2 is a diagram of an embodiment of the present invention.
Figure 1 has been discussed in the introductory part of the description. In Figure 2, an apparatus 220 for impregnating fibrous reinforcement materials with a resin matrix is shown which comprises means 200,202 for feeding a reinforcement material 206 between a surface for depositing resin 200 and a member 202 for contacting the reinforcement material with the deposit surface, wherein the deposit surface 200 is continuous, said surface comprising at least one resin receiving portion 204 and at least one resin depositing portion.
The feeding means are in the form of first and second continuous belt 200, 202. The first belt 200 is positioned above the second 202 with a spacing of between 0.05 to 5 mm between them depending on the amount of pressure that is to be exerted on the resin during contacting to impregnate the reinforcement material. Both belts 200,202 comprise a PTFE surface material. A resin film is deposited on the upward facing surface of the first belt 204 using a knife over roll process. A sheet of fibrous reinforcement 206 is unwound from a drum or from creels and is pressed into the surface of resin. The fibrous reinforcement may be heated using an infrared lamp for example, before it is pressed into the resin. The resin and fibrous reinforcement move with the belt in the direction labelled on the diagram as 205. As the resin moves over the top surface of the first belt it is heated by a hot plate 209 to lower the viscosity of the resin.
The resin then comes into contact with the second belt 202 which presses the fibrous reinforcement into the resin. Impregnation continues whilst the prepreg is in contact with both belts. The increased area of contact along the length of the belts ensures a high degree of impregnation can be achieved. Optionally the path taken by belts may deviate around rollers to further work the resin into the prepreg. Further heating is also provided by hot plates on both of the belts 208. Cooling plates 210 at the ends of the belts cool the resin to allow the prepreg to be removed from between the belts. The prepreg is then cured on line by the application of heat (not shown) or a protective sheet 211 is applied before being wound onto a drum 212.
EXAMPLE OF THE INVENTION
Prepreg was produced using a PTFE double belt press as described in Figure 2 using BB600 and LBB1200 glass fibre fabric and M9.6 resin (supplied by Hexcel Holding GmbH). The press had a first belt of approximately 12m length positioned above a second belt of similar length. The belts had a width of 1.4 m. The heating zone was 2.3m long in total and could heat with a power of 180kW achieving a maximum temperature of 220°C. The belts could achieve a pressure up to 50 N/cm2.
The water pick-up test was used to determine the degree of impregnation of the prepreg material produced using the method of this invention. In this test, a specimen of prepreg material was cut to 40mm by 10 mm. It was then initially weighed (wl) and clamped between two plates in such a way that a strip 5 mm wide protruded. This arrangement was suspended in a water bath at room temperature (21°C) for 5 minutes. The specimen was then removed from the plates and excess water was removed from the surface then weighed again (w2). The difference in weight provides a value for the degree of impregnation within the specimen. The smaller the amount of water picked up, the higher the degree of impregnation. WPU (water pick up, %) = (w2 - wl)/wl x 100.
Both prepregs were impregnated to have a resin content of 50%. TheBB600 prepreg had an average WPU of 0.4 % when produced with a line speed of 4 m/min and a WPU of 1.2% with a line speed of 7 m/min. The LBB1200 prepreg had a WPU of 1% with a line speed of 4 m/min.

Claims (12)

1. An apparatus for impregnating fibrous reinforcement materials with a resin matrix comprising means for feeding a reinforcement material between a surface for depositing resin and a member for contacting the reinforcement material with the deposit surface, wherein the deposit surface is continuous, said surface comprising at least one resin receiving portion and at least one resin depositing portion.
2. An apparatus of claim 1, wherein the resin receiving portion and the resin depositing portion are spaced in relation to one another.
3. An apparatus of claim 1 or claim 2, wherein the contact member may comprise a further deposit surface, said surface comprising at least one further resin receiving portion and at least one further resin depositing portion.
4. An apparatus according to any of the preceding claims wherein the deposit surface is cylindrical.
5. An apparatus according to any of the preceding claims wherein the deposit surface is located on a belt.
6. An apparatus according to any of the preceding claims, wherein the apparatus comprises means for conditioning the resin.
7. An apparatus according to any of the preceding claims, wherein the reinforcement material contacted with resin forms a prepreg.
8. A method for impregnating fibrous reinforcement materials with a resin matrix comprising feeding a reinforcement material between a contact member and a surface for depositing resin, and contacting the reinforcement material with the deposit surface, wherein the deposit surface is continuous, and said deposit surface comprises at least one resin receiving portion and at least one resin depositing portion.
9. A method according to claim 8, wherein the reinforcement material is resin impregnated directly without the use of an intermediate step or backing sheet material.
10. A method according to claim 8 or 9, wherein the resin matrix material is heated and pressed on to the fibrous reinforcement to form a prepreg.
11. A method according to any of claims 8 to 10, wherein a further deposit surface provides the step of contacting, said further deposit surface comprising at least one further resin receiving portion and at least one further resin depositing portion.
12. A method according to any of claims 8 to 11, wherein the method further comprises the step of curing the resin following impregnation. A method according to any of claims 8 to 12, wherein the method comprises an additional step of cleaning resin from the deposit surface.
GB1522516.2A 2015-12-21 2015-12-21 Apparatus and method of impregnating reinforcement material Withdrawn GB2546962A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1522516.2A GB2546962A (en) 2015-12-21 2015-12-21 Apparatus and method of impregnating reinforcement material

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1522516.2A GB2546962A (en) 2015-12-21 2015-12-21 Apparatus and method of impregnating reinforcement material

Publications (2)

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GB201522516D0 GB201522516D0 (en) 2016-02-03
GB2546962A true GB2546962A (en) 2017-08-09

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001090482A2 (en) * 2000-05-23 2001-11-29 Hoegfors Christian Process for manufacturing a fibre web comprising a thermosetting resin, such a fibre web, and a reinforced fibre web comprising a thermosetting resin composite
US20040062858A1 (en) * 2001-12-18 2004-04-01 Tetsuro Sato Prepreg production method and prepeg production device and prepreg obtained by the production method and production method for insulating layer attached copper foil and insulating layer attached copper foil obtained by the production method
EP3081368A1 (en) * 2015-04-14 2016-10-19 Leichtbau-Zentrum Sachsen GmbH Plastic composite fiber semi-finished product and method for preparation

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001090482A2 (en) * 2000-05-23 2001-11-29 Hoegfors Christian Process for manufacturing a fibre web comprising a thermosetting resin, such a fibre web, and a reinforced fibre web comprising a thermosetting resin composite
US20040062858A1 (en) * 2001-12-18 2004-04-01 Tetsuro Sato Prepreg production method and prepeg production device and prepreg obtained by the production method and production method for insulating layer attached copper foil and insulating layer attached copper foil obtained by the production method
EP3081368A1 (en) * 2015-04-14 2016-10-19 Leichtbau-Zentrum Sachsen GmbH Plastic composite fiber semi-finished product and method for preparation

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Publication number Publication date
GB201522516D0 (en) 2016-02-03

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