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WO1994019176A1 - Method for manufacturing fibre composites - Google Patents

Method for manufacturing fibre composites Download PDF

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Publication number
WO1994019176A1
WO1994019176A1 PCT/SE1994/000136 SE9400136W WO9419176A1 WO 1994019176 A1 WO1994019176 A1 WO 1994019176A1 SE 9400136 W SE9400136 W SE 9400136W WO 9419176 A1 WO9419176 A1 WO 9419176A1
Authority
WO
WIPO (PCT)
Prior art keywords
injection channel
mould
cavity
during
resin
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.)
Ceased
Application number
PCT/SE1994/000136
Other languages
French (fr)
Inventor
Joakim Pettersson
Erik Sandlund
Anders STRÖMBECK
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.)
SWEDISH INSTITUTE OF COMPOSITES SICOMP
Original Assignee
SWEDISH INSTITUTE OF COMPOSITES SICOMP
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 SWEDISH INSTITUTE OF COMPOSITES SICOMP filed Critical SWEDISH INSTITUTE OF COMPOSITES SICOMP
Priority to AU61592/94A priority Critical patent/AU6159294A/en
Priority to EP94908546A priority patent/EP0686084A1/en
Publication of WO1994019176A1 publication Critical patent/WO1994019176A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/54—Component parts, details or accessories; Auxiliary operations, e.g. feeding or storage of prepregs or SMC after impregnation or during ageing
    • B29C70/546—Measures for feeding or distributing the matrix material in the reinforcing structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/40—Shaping or impregnating by compression not applied
    • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/46—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
    • B29C70/462—Moulding structures having an axis of symmetry or at least one channel, e.g. tubular structures, frames
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/40—Shaping or impregnating by compression not applied
    • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/46—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
    • B29C70/48—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs and impregnating the reinforcements in the closed mould, e.g. resin transfer moulding [RTM], e.g. by vacuum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2023/00—Tubular articles
    • B29L2023/22—Tubes or pipes, i.e. rigid

Definitions

  • the invention relates to a method of manufacturing polymeric fibre composites by injecting a polymer material in a forming tool, a mould, comprising a prelocated fibre reinforcement which is usually called Resin Transfer Moulding (RTM) , Injection, Resinject or Liquid Composite Moulding.
  • RTM Resin Transfer Moulding
  • the invention relates to a method by means of which a good and ensured mould filling, without air inclu ⁇ sions or other unwanted inhomogeneities, is obtained while at the same time the fill time is considerably reduced.
  • RTM is used for manufacturing a large number of polymeric composite products.
  • the process can be used for both large and small objects, for products with high performance requirements and regardless of geometrical complexity. Further, the flexibility of the process is great with respect to the material choice for both fibre reinforcement and polymer matrix.
  • Common matrix materials are thermosetting resins such as unsaturated polyester and epoxy. All common fibre types which are used for the purpose of reinforcement, such as glass fibre, carbon fibre, thermoplastic polymeric fibre materials, ceramic whiskers materials and metallic fibres can be used during the process.
  • RTM process can be described to comprise the following steps:
  • the process places demands on the physical properties of the polymeric matrix material and on a good control of its change during the curing stage.
  • the mould filling requirement means that the liquid polymeric matrix material must exhibit a sufficiently low viscosity and maintain this until the whole forming tool (mould) is filled in spite of the fact that the curing sometimes is started as early as during the mould filling stage.
  • the formed part should rapidly reach a stiffness after completed mould filling, in that the curing reaches such a level that the part can be removed from the tool without any extended residence time and be stripped, thus obtaining a high productivity.
  • the RTM mould comprises two or more tool parts which during mould filling and curing define a cavity with the geometry of the part.
  • the mould is always adapted to comprise at least one gate for supply of the liquid polymeric matrix material and at least one deaeration port for evacuating air present in the mould during the mould filling.
  • the positioning and the design of the gate and the deaeration ports are comple ⁇ tely decisive for achieving a good mould filling. It is common to apply through the deaeration ports a ⁇ ubatmospheric pressure in the mould in order to increase the pressure difference between the gate and the flow front and hence reduce the time for the mould filling.
  • the use of vacuum, subatmospheric pressure normally also reduces the content of air inclusions, pores.
  • the polymeric matrix material is pressed in through the gate at a low pressure, injection pressure, of 0.1 - 1 MPa, which means that the force, the locking force, holding the mould together can be limited. At the same time, it means that the forces acting on the mould surfaces become low whereby good geometrical tolerances can be obtained also with relatively simple mould designs. Taken together, this means that the investment costs for the RTM process are low on a comparison with other processes for forming fibre composites, especially processes for forming high-performance fibre composites.
  • the mould filling is a very critical process step during which it is required that the fibre reinforcement placed in the cavity is filled up completely without air inclusions, pores, remaining in the formed part.
  • the mould fill time should be short to attain a high productivity.
  • Complete filling of the cavity and of the so-called free volume in the fibre reinforcement is achieved in the simplest way with simple and symmetrical geometries and with a fibre content in the whole fibre reinforcement which i ⁇ evenly distributed in the cavity.
  • Mould filling, pore content and fill time are thus influenced by a plurality of more or less cooperating parameters, such as injection pressure, subatmospheric pressure in the mould, the viscosity of the polymeric matrix material, its wetting properties relative to the fibre reinforcement, and the sur- faces of the mould, the injection distance, and the permea ⁇ bility of the fibre reinforcement.
  • mould filling and the mould fill time can be changed by the choice of mould filling strategy.
  • Two funda ⁇ mentally different strategies are normally used:
  • Point injection by which is meant that one or more gates is or are placed near the centre of the part and that the flow front propagates from the gate/s in all directions out towards the edges of the part where deaeration takes place through one or more deaeration ports.
  • Edge injection by which is meant that one or more gates is or are placed along one or more of the edges of the cavity via a runner or distribution channel.
  • the distribution channel i ⁇ adapted to supply polymer through gates which are essentially placed along an edge or a side surface
  • the flow front propagates during the form filling in a direction away from this edge or side surface towards the opposite side surface or surfaces where deaeration takes place.
  • the distribution channel and the gate are adapted to supply polymer from the edges or side surfaces which constitute the outer limiting surface or periphery of the part, the flow front propagates during the mould filling away from the periphery towards the centre where deaeration takes place.
  • edge injection provides a shorter fill time than point injection for the same part and with the same proce ⁇ parameters.
  • the permeability of the fibre reinforcement is of decisive importance for the mould fill time.
  • the permeability in the reinforcement i ⁇ primarily determined by the volumetric con- tent of fibre in the fibre reinforcement.
  • High fibre con ⁇ tents which occur in high-performance polymeric fibre com- po ⁇ ites, provide considerable resistance for the liquid poly ⁇ mer compound, the resin, to impregnate the fibre reinforce ⁇ ment whereby the fill time becomes unacceptably long.
  • the curing is influenced in a negative way since the curing process must be adapted to fulfil the requirement for a low resin visco ⁇ ity during e ⁇ entially the entire form fill time.
  • One object of the invented method is to offer a process during which a liquid polymer material with a minimized mould fill time is supplied and fills up a mould defined by a cavity in a forming tool and impregnates a preform of fibre reinforcement arranged in this mould. Further, the invented method provides a complete mould filling with a minimized pore content and a qualitatively repeatable mould filling under controllable conditions.
  • a forming tool (a mould) is adapted to define a cavity, whereupon a preformed fibre reinforcement is placed in the cavity before a liquid resin of a low-viscous polymer material is supplied to the cavity.
  • the cavity is filled essentially completely with polymer material whereby the fibre reinforcement is impregnated es ⁇ entially completely by the polymer material.
  • the viscosity of the polymer material has been increased by curing to impart to the formed fibre composite body a stiffne ⁇ s which permits the formed fibre composite body to be handled, it is stripped.
  • the cavity is filled with resin through one or more injection channels centrally arranged in the fibre reinforcement.
  • the resin is inserted into the mould through a gate arranged on the gate side of the injection channel, and during the mould filling the injection channel is extended in a controlled manner to control the supply of resin such that the flow front of the resin, while filling the cavity and impregnating the fibre reinforcement with resin, propagates es ⁇ entially parallel to the axi ⁇ of the injection channel through the cavity as the injection channel is extended into the cavity.
  • the invented method is e ⁇ pecially ⁇ uitable for two type ⁇ of compo ⁇ ite product ⁇ for which the preformed fibre reinforce ⁇ ment comprise cavitie ⁇ which re ⁇ ult in hollow article ⁇ or parts compri ⁇ ing both reinforced and non-reinforced portion ⁇ , ⁇ o-called sandwich designs.
  • es ⁇ entially cylindri- cal injection channel ⁇ are arranged in the ⁇ e non-reinforced cavities.
  • the injection channel can be defined as a tube, a liner, with walls permeable to the resin, or be formed by the fibre reinforcement or as a cavity in a core permeable to the resin.
  • the injection channel can be straight or cylindrical but also be provided with contours which follow the geometry of the formed body.
  • the above-mentioned piston is divided into two parts, with one inner stationary shaft which remains in the cavity during the mould filling to minimize the volume of the injection channel, and one outer ⁇ leeve which i ⁇ arranged concentric with the above-mentioned ⁇ haft and which during the mould filling i ⁇ pressed out or withdrawn, in the manner described above, from a hole arranged at that end of the injection channel which i ⁇ oppo ⁇ ite to the gate.
  • the mould fill time is minimized in that during the entire mould fill time the distance from freely floating re ⁇ in in the injection channel to the flow front which propagate ⁇ through the fibre reinforcement i ⁇ ⁇ mall and constant, which on a compari ⁇ on with conventional RTM technique greatly reduces the mould fill time in connection with:
  • the invented method is very advantageous for the manufacture of long, hollow products such as high-performance tubes, tube ⁇ with integrated flange ⁇ and for drive ⁇ haft ⁇ , a ⁇ well a ⁇ for integrated manufacture of complex part ⁇ ⁇ uch as the manufacture of guide surface ⁇ , including ⁇ haft and attach ⁇ ment, in one ⁇ tep.
  • the invented method i ⁇ also very valuable for manufacturing composites with high-viscou ⁇ matrix ⁇ ystem ⁇ such as high- temperature resi ⁇ tant thermo ⁇ etting re ⁇ in ⁇ , high- ⁇ trength thermosetting re ⁇ ins and thermoplastic resins.
  • Figure 1 shows a method according to the invention where the propagation of the flow front is controlled with the aid of a piston arranged in the injection channel
  • Figure 2 shows an embodiment where the propagation of the flow front is controlled by turning a hose, arranged in the injection channel, inside out during mould filling and with ⁇ drawing it from the injection channel
  • a hose arranged in the injection channel
  • Figure 3 show ⁇ an embodiment through which the volume of the injection channel is minimized during the mould filling.
  • a preformed fibre reinforcement 11 is placed in a forming tool, a mould, 12.
  • a cylindrical injection channel 13 is arranged in the fibre reinforcement 11 .
  • a piston 14 i ⁇ in ⁇ erted into the injection channel 13 through a hole 15 in the mould 12.
  • the pi ⁇ ton 14 In in ⁇ erted position the pi ⁇ ton 14 e ⁇ entially fill ⁇ up all the volume of the injection channel 13 and can be freely moved in the injection channel 13.
  • a gate 16 is provided in the forming tool 12 and open ⁇ out at one end of the injection channel 13, the gate ⁇ ide 17, wherea ⁇ the outlet hole 15 of the pi ⁇ ton is provided at the other end 18 of the injection channel.
  • Deaeration point ⁇ in the form of ports (not ⁇ hown) are arranged, a ⁇ i ⁇ the ca ⁇ e with conventional manufacture according to the RTM technique, ba ⁇ ed on the geometry of the part. Re ⁇ in i ⁇ ⁇ upplied during the mould filling through the gate 16, provided on the gate side 17 of the injection channel 13, with a con ⁇ tant pres ⁇ ure and flow.
  • the pi ⁇ ton 14 take ⁇ up essentially all of the volume of the injection channel 13.
  • the piston 14 is then moved in a controlled manner such that a flow front 19 is formed which, during the mould filling, propagates with a constant and small advance, X, in relation to the extension of the injection channel 13 controlled by the movement of the piston.
  • the flow resistance in the injec ⁇ tion channel 13 is small and negligible relative to the flow re ⁇ i ⁇ tance in the preformed fibre reinforcement 11, which re ⁇ ults in a small pres ⁇ ure drop in the injection channel 13 during the mould filling.
  • the pre ⁇ ure difference between the injection channel 13 and the flow front 19 is all the time constant, which is equivalent to a situation where resin is supplied through a gate which e ⁇ entially follow ⁇ the flow front 19 during its propagation along the injection channel 13 during the mould filling. Thi ⁇ great pre ⁇ ure difference over a ⁇ hort di ⁇ tance is maintained during essentially the whole mould filling proces ⁇ .
  • the mould filling is terminated by retur- ning the piston 14 to its initial po ⁇ ition, which empties the injection channel 13 with a reversed flow out through the gate 16.
  • the curing stage sets in during which the stiffne ⁇ of the polymer material i ⁇ increa ⁇ ed u ⁇ ing a tech ⁇ nique which i ⁇ relevant for the polymer material in que ⁇ tion.
  • the formed compo ⁇ ite body ha ⁇ reached a sufficient stiffne ⁇ , it i ⁇ ⁇ tripped using conventional methods for ordinary manufacture by means of RTM technique.
  • the piston function can be achieved using a hose turned inside out.
  • a preformed fibre reinforcement 21 i ⁇ placed in a mould 22.
  • a hose 24 is in ⁇ erted through a hole 25 in the forming tool 22.
  • the ho ⁇ e 24, which at its inserted end 241 is turned inside out and clo ⁇ ed, essentially fill ⁇ up the entire volume of the injection channel 23 by applying an internal overpre ⁇ ure to the ho ⁇ e 24.
  • a gate 36 is arranged in the mould 32 and opens out at one end of the injection channel 33, the gate ⁇ ide 37, wherea ⁇ the outlet hole 35 of the ⁇ leeve i ⁇ arranged at the other end 38 of the injection channel. During the mould filling resin is supplied, with a controlled pre ⁇ sure and flow, through the gate 36 arranged on the gate side 37 of the injection channel 33.
  • the sleeve 34b essentially takes up the whole volume of the injection channel 33. Then the sleeve 34b is moved in a controlled manner such that a flow front 39 is formed, in the manner described above, and propagate ⁇ during the mould filling proce ⁇ in a controlled manner essentially parallel to the axis of the injection channel 33 through the cavity.
  • the mould filling i ⁇ completed by moving the ⁇ leeve 34b back to the initial po ⁇ ition, which empties the injection channel 33 with a rever ⁇ ed flow out through the gate 36. Thereafter, the formed compo ⁇ ite body i ⁇ cured and stripped in the manner described above.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Composite Materials (AREA)
  • Mechanical Engineering (AREA)
  • Moulding By Coating Moulds (AREA)
  • Reinforced Plastic Materials (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Abstract

A method of manufacturing bodies of polymeric fibre composites, wherein a preformed fibre reinforcement (11, 21, 31, 41, 51) is placed in a cavity whereupon a liquid resin of a low-viscous polymer material is supplied to the cavity through one or more injection channels (13, 23, 33, 43, 53) provided in the fibre reinforcement, whereby the resin supply through the injection channel is controlled such that the flow front (19, 29, 39, 49, 59) of the resin during the mould filling propagates parallel to the axis of said injection channel through the cavity such that the fibre reinforcement is impregnated by the polymer material, the viscosity of the polymer material then being increased and the body being stripped.

Description

Method for manufacturing fibre composites
TECHNICAL FIELD
The invention relates to a method of manufacturing polymeric fibre composites by injecting a polymer material in a forming tool, a mould, comprising a prelocated fibre reinforcement which is usually called Resin Transfer Moulding (RTM) , Injection, Resinject or Liquid Composite Moulding. Herein- after, the designation RTM will be used in this application.
More specifically, the invention relates to a method by means of which a good and ensured mould filling, without air inclu¬ sions or other unwanted inhomogeneities, is obtained while at the same time the fill time is considerably reduced.
BACKGROUND ART
RTM is used for manufacturing a large number of polymeric composite products. The process can be used for both large and small objects, for products with high performance requirements and regardless of geometrical complexity. Further, the flexibility of the process is great with respect to the material choice for both fibre reinforcement and polymer matrix. Common matrix materials are thermosetting resins such as unsaturated polyester and epoxy. All common fibre types which are used for the purpose of reinforcement, such as glass fibre, carbon fibre, thermoplastic polymeric fibre materials, ceramic whiskers materials and metallic fibres can be used during the process.
In simplified terms, the RTM process can be described to comprise the following steps:
1) placing the fibre material in a forming tool, a mould, 2) locking all mould parts,
3) filling the mould by injecting a liquid polymer into the tool through one or more gates, whereupon the tool is dea- erated through one or more deaeration points,
4) curing the polymer material in the mould, and
5) opening the mould and stripping the formed part.
The process places demands on the physical properties of the polymeric matrix material and on a good control of its change during the curing stage. The mould filling requirement means that the liquid polymeric matrix material must exhibit a sufficiently low viscosity and maintain this until the whole forming tool (mould) is filled in spite of the fact that the curing sometimes is started as early as during the mould filling stage. At the same time, the formed part should rapidly reach a stiffness after completed mould filling, in that the curing reaches such a level that the part can be removed from the tool without any extended residence time and be stripped, thus obtaining a high productivity.
The RTM mould comprises two or more tool parts which during mould filling and curing define a cavity with the geometry of the part. The mould is always adapted to comprise at least one gate for supply of the liquid polymeric matrix material and at least one deaeration port for evacuating air present in the mould during the mould filling. The positioning and the design of the gate and the deaeration ports are comple¬ tely decisive for achieving a good mould filling. It is common to apply through the deaeration ports a εubatmospheric pressure in the mould in order to increase the pressure difference between the gate and the flow front and hence reduce the time for the mould filling. The use of vacuum, subatmospheric pressure, normally also reduces the content of air inclusions, pores.
Typically, the polymeric matrix material is pressed in through the gate at a low pressure, injection pressure, of 0.1 - 1 MPa, which means that the force, the locking force, holding the mould together can be limited. At the same time, it means that the forces acting on the mould surfaces become low whereby good geometrical tolerances can be obtained also with relatively simple mould designs. Taken together, this means that the investment costs for the RTM process are low on a comparison with other processes for forming fibre composites, especially processes for forming high-performance fibre composites.
The mould filling is a very critical process step during which it is required that the fibre reinforcement placed in the cavity is filled up completely without air inclusions, pores, remaining in the formed part. In addition, it is required that the mould fill time should be short to attain a high productivity. Complete filling of the cavity and of the so-called free volume in the fibre reinforcement is achieved in the simplest way with simple and symmetrical geometries and with a fibre content in the whole fibre reinforcement which iε evenly distributed in the cavity. For more complex geometries or with a fibre reinforcement with a varying fibre content or a fibre reinforcement unevenly distributed in the cavity, it is often difficult to achieve a good form filling and/or a low pore content.
Mould filling, pore content and fill time are thus influenced by a plurality of more or less cooperating parameters, such as injection pressure, subatmospheric pressure in the mould, the viscosity of the polymeric matrix material, its wetting properties relative to the fibre reinforcement, and the sur- faces of the mould, the injection distance, and the permea¬ bility of the fibre reinforcement.
Further, the mould filling and the mould fill time can be changed by the choice of mould filling strategy. Two funda¬ mentally different strategies are normally used:
A. Point injection, by which is meant that one or more gates is or are placed near the centre of the part and that the flow front propagates from the gate/s in all directions out towards the edges of the part where deaeration takes place through one or more deaeration ports.
B. Edge injection, by which is meant that one or more gates is or are placed along one or more of the edges of the cavity via a runner or distribution channel. When the distribution channel iε adapted to supply polymer through gates which are essentially placed along an edge or a side surface, the flow front propagates during the form filling in a direction away from this edge or side surface towards the opposite side surface or surfaces where deaeration takes place. When the distribution channel and the gate are adapted to supply polymer from the edges or side surfaces which constitute the outer limiting surface or periphery of the part, the flow front propagates during the mould filling away from the periphery towards the centre where deaeration takes place.
Generally, edge injection provides a shorter fill time than point injection for the same part and with the same proceεε parameters.
The permeability of the fibre reinforcement is of decisive importance for the mould fill time. The permeability in the reinforcement iε primarily determined by the volumetric con- tent of fibre in the fibre reinforcement. High fibre con¬ tents, which occur in high-performance polymeric fibre com- poεites, provide considerable resistance for the liquid poly¬ mer compound, the resin, to impregnate the fibre reinforce¬ ment whereby the fill time becomes unacceptably long. When the fill time is long, also the curing is influenced in a negative way since the curing process must be adapted to fulfil the requirement for a low resin viscoεity during eεεentially the entire form fill time. For many resin materials, the requirements for a retained low viscoεity during a long form fill time to enεure good filling and low pore content cannot be combined with the requirements for a rapid curing process in a subsequent curing stage, but usually it is necessary to compromise between theεe require¬ ments. At a constant injection pressure, this usually results in a reduction of the rate of the flow front such that the total form fill time is proportional to the square of the injection distance. In this way, the mould fill time will be unreasonably long for large parts unless a large number of gates can be arranged to shorten the necessary injection distances. However, a large number of gates render the moulds more complicated and expensive.
One object of the invented method is to offer a process during which a liquid polymer material with a minimized mould fill time is supplied and fills up a mould defined by a cavity in a forming tool and impregnates a preform of fibre reinforcement arranged in this mould. Further, the invented method provides a complete mould filling with a minimized pore content and a qualitatively repeatable mould filling under controllable conditions.
SUMMARY OF THE INVENTION
When manufacturing polymeric fibre composite bodies using the RTM technique, a forming tool (a mould) is adapted to define a cavity, whereupon a preformed fibre reinforcement is placed in the cavity before a liquid resin of a low-viscous polymer material is supplied to the cavity. The cavity is filled essentially completely with polymer material whereby the fibre reinforcement is impregnated esεentially completely by the polymer material. When the viscosity of the polymer material has been increased by curing to impart to the formed fibre composite body a stiffneεs which permits the formed fibre composite body to be handled, it is stripped. During the mould filling, the cavity is filled with resin through one or more injection channels centrally arranged in the fibre reinforcement. According to the invented method, the resin is inserted into the mould through a gate arranged on the gate side of the injection channel, and during the mould filling the injection channel is extended in a controlled manner to control the supply of resin such that the flow front of the resin, while filling the cavity and impregnating the fibre reinforcement with resin, propagates esεentially parallel to the axiε of the injection channel through the cavity as the injection channel is extended into the cavity.
The invented method is eεpecially εuitable for two typeε of compoεite productε for which the preformed fibre reinforce¬ ment comprise cavitieε which reεult in hollow articleε or parts compriεing both reinforced and non-reinforced portionε, εo-called sandwich designs. Preferably, esεentially cylindri- cal injection channelε are arranged in theεe non-reinforced cavities. The injection channel can be defined as a tube, a liner, with walls permeable to the resin, or be formed by the fibre reinforcement or as a cavity in a core permeable to the resin. The injection channel can be straight or cylindrical but also be provided with contours which follow the geometry of the formed body.
This is achieved in one embodiment of the invention by arranging a piston in the injection channel and when reεin during the form filling is supplied through a gate at one end of the injection channel, the piston is withdrawn or pressed out of its inserted position through a hole provided at the other end of the injection channel, whereby the injection channel is extended during the mould filling and the flow front of the resin propagates essentially parallel to the axis of the injection channel.
The same effect is achieved when the above-mentioned piεton in another embodiment of the invention iε arranged in the form of a hose which during the mould filling is turned inside out and is withdrawn from the injection channel through a hole arranged at that end of the injection channel which is oppoεite to the gate.
According to a further embodiment of the invention, the above-mentioned piston is divided into two parts, with one inner stationary shaft which remains in the cavity during the mould filling to minimize the volume of the injection channel, and one outer εleeve which iε arranged concentric with the above-mentioned εhaft and which during the mould filling iε pressed out or withdrawn, in the manner described above, from a hole arranged at that end of the injection channel which iε oppoεite to the gate.
When manufacturing polymeric fibre compoεiteε according to the invented method, the mould fill time is minimized in that during the entire mould fill time the distance from freely floating reεin in the injection channel to the flow front which propagateε through the fibre reinforcement iε εmall and constant, which on a compariεon with conventional RTM technique greatly reduces the mould fill time in connection with:
- large and/or long bodies,
- bodies with a high fibre content, and - matrix polymers with a high viscosity. In addition, because of the short distance from freely floa¬ ting resin in the injection channel to the flow front through the fibre reinforcement obtained with the invented method, a good control is obtained of the mould filling process, which is thereby controlled by the movements of the piston.
With the invented method, a supply of material is obtained which during the mould filling takeε place in a controlled manner from the injection channel or the channels in the interior of the body, which is favourable to avoid air incluεions and other inhomogeneities which may be due to a disturbed material flow through the fibre reinforcement.
The invented method is very advantageous for the manufacture of long, hollow products such as high-performance tubes, tubeε with integrated flangeε and for drive εhaftε, aε well aε for integrated manufacture of complex partε εuch as the manufacture of guide surfaceε, including εhaft and attach¬ ment, in one εtep.
The invented method iε also very valuable for manufacturing composites with high-viscouε matrix εystemε such as high- temperature resiεtant thermoεetting reεinε, high-εtrength thermosetting reεins and thermoplastic resins.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be explained in greater detail and be exemplified by means of a number of preferred embodiments with reference to the accompanying drawingε wherein
Figure 1 shows a method according to the invention where the propagation of the flow front is controlled with the aid of a piston arranged in the injection channel, Figure 2 shows an embodiment where the propagation of the flow front is controlled by turning a hose, arranged in the injection channel, inside out during mould filling and with¬ drawing it from the injection channel, and
Figure 3 showε an embodiment through which the volume of the injection channel is minimized during the mould filling.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
When manufacturing a polymer composite body uεing RTM technique according to one embodiment of the invented method shown in Figure 1, a preformed fibre reinforcement 11 is placed in a forming tool, a mould, 12. In the fibre reinforcement 11 a cylindrical injection channel 13 is arranged. A piston 14 iε inεerted into the injection channel 13 through a hole 15 in the mould 12.
In inεerted position the piεton 14 eεεentially fillε up all the volume of the injection channel 13 and can be freely moved in the injection channel 13. A gate 16 is provided in the forming tool 12 and openε out at one end of the injection channel 13, the gate εide 17, whereaε the outlet hole 15 of the piεton is provided at the other end 18 of the injection channel. Deaeration pointε in the form of ports (not εhown) are arranged, aε iε the caεe with conventional manufacture according to the RTM technique, baεed on the geometry of the part. Reεin iε εupplied during the mould filling through the gate 16, provided on the gate side 17 of the injection channel 13, with a conεtant presεure and flow. At the beginn¬ ing of the mould filling operation, the piεton 14 takeε up essentially all of the volume of the injection channel 13. The piston 14 is then moved in a controlled manner such that a flow front 19 is formed which, during the mould filling, propagates with a constant and small advance, X, in relation to the extension of the injection channel 13 controlled by the movement of the piston. The flow resistance in the injec¬ tion channel 13 is small and negligible relative to the flow reεiεtance in the preformed fibre reinforcement 11, which reεults in a small presεure drop in the injection channel 13 during the mould filling. The preεεure difference between the injection channel 13 and the flow front 19 is all the time constant, which is equivalent to a situation where resin is supplied through a gate which eεεentially followε the flow front 19 during its propagation along the injection channel 13 during the mould filling. Thiε great preεεure difference over a εhort diεtance is maintained during essentially the whole mould filling procesε. When eεεentially the whole free volume of the fibre reinforcement 11 has been replaced by polymer material, the mould filling is terminated by retur- ning the piston 14 to its initial poεition, which empties the injection channel 13 with a reversed flow out through the gate 16. Then, the curing stage sets in during which the stiffneεε of the polymer material iε increaεed uεing a tech¬ nique which iε relevant for the polymer material in queεtion. When the formed compoεite body haε reached a sufficient stiffneεε, it iε εtripped using conventional methods for ordinary manufacture by means of RTM technique.
As is clear from the embodiment shown in Figure 2, the piston function can be achieved using a hose turned inside out. A preformed fibre reinforcement 21 iε placed in a mould 22. Into an injection channel 23 arranged in the fibre rein¬ forcement 21, a hose 24 is inεerted through a hole 25 in the forming tool 22. At the beginning of the mould filling, the hoεe 24, which at its inserted end 241 is turned inside out and cloεed, essentially fillε up the entire volume of the injection channel 23 by applying an internal overpreεεure to the hoεe 24. A rod or line 242, arranged inεide the hoεe 24, iε attached to the end 241 turned inside out. Since the rod 242 during the mould filling is withdrawn from the hole 25, the hose 24 iε turned inεide and likewiεe withdrawn from the
Figure imgf000013_0001
εide the sleeve 34b. The sleeve 34b runs between this sealing layer 34c, which is stationarily secured to the piston 34a, and the piston 34a to presε out the εealing layer so that it seals off the injection channel 33. A gate 36 is arranged in the mould 32 and opens out at one end of the injection channel 33, the gate εide 37, whereaε the outlet hole 35 of the εleeve iε arranged at the other end 38 of the injection channel. During the mould filling resin is supplied, with a controlled preεsure and flow, through the gate 36 arranged on the gate side 37 of the injection channel 33. At the start of the mould filling procesε, the sleeve 34b essentially takes up the whole volume of the injection channel 33. Then the sleeve 34b is moved in a controlled manner such that a flow front 39 is formed, in the manner described above, and propagateε during the mould filling proceεε in a controlled manner essentially parallel to the axis of the injection channel 33 through the cavity. When esεentially the whole free volume of the fibre reinforcement 31 haε been replaced by polymer material, the mould filling iε completed by moving the εleeve 34b back to the initial poεition, which empties the injection channel 33 with a reverεed flow out through the gate 36. Thereafter, the formed compoεite body iε cured and stripped in the manner described above.

Claims

1. A method of manufacturing bodies of polymeric fibre compo¬ site in a forming tool, a mould, which is adapted to define a cavity, wherein a preformed fibre reinforcement is placed in the cavity whereupon a liquid resin of a low-viscous polymer material is supplied to the cavity such that the cavity is eεsentially filled with polymer material and said fibre reinforcement is impregnated essentially completely by the polymer material during the mould filling whereafter the viscoεity of the polymer material is increased such that the body is given a stiffnesε where the formed fibre compoεite body can be stripped, wherein said resin is supplied to the cavity through one or more injection channels (13, 23, 33, 43, 53) provided in the fibre reinforcement (11, 21, 31, 41, 51) , characterized in that said resin is inserted into the mould through a hole, a gate, (16, 26, 36) provided on the gate side (17, 27, 37) of the injection channel and that the injection channel, during the mould filling, is extended in a controlled manner to control the supply of resin such that the flow front (19, 29, 39, 49, 59) of the resin during the form filling propagates esεentially parallel to the axiε of εaid injection channel through the cavity.
2. A method according to claim 1, characterized in that a piston (14, 24, 34) iε arranged in εaid injection channel,, whereby εaid piston during the mould filling is withdrawn from or presεed out through a hole (15, 25, 35) arranged at that end (18, 28, 38) of the injection channel which iε opposite to the gate side, whereby the extension of the injection channel is controlled and the supply of the resin is controlled such that the flow front (19, 29, 39) of the resin during the mould filling propagates esεentially parallel to the axis of said injection channel through the cavity.
3. A method according to claim 2, characterized in that εaid piston is arranged in the form of a hose which, during the mould filling, is turned inside out and withdrawn from that end of the injection channel which is opposite to the gate side.
4. A method according to claim 2, characterized in that εaid piεton iε arranged in two parts with one inner εtatio- nary shaft (34a) , which remains in the cavity during the mould filling, and one outer sleeve (34b) which iε concentric with εaid shaft and which during the mould filling is presεed or withdrawn through a hole (35) arranged at that end (38) of the injection channel (33) which iε opposite to the gate side
(37) .
PCT/SE1994/000136 1993-02-25 1994-02-18 Method for manufacturing fibre composites Ceased WO1994019176A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU61592/94A AU6159294A (en) 1993-02-25 1994-02-18 Method for manufacturing fibre composites
EP94908546A EP0686084A1 (en) 1993-02-25 1994-02-18 Method for manufacturing fibre composites

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9300639-3 1993-02-25
SE9300639A SE501085C2 (en) 1993-02-25 1993-02-25 Method for manufacturing bodies of fiber composites

Publications (1)

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WO2000056515A1 (en) * 1999-03-19 2000-09-28 Dag Thulin Apparatus for facilitating extraction of supply conduits for thermosetting resin from a mould cavity
DE10023208A1 (en) * 2000-05-12 2001-11-15 Alstom Power Nv Insulation of stator windings by injection molding
DE102013215384A1 (en) * 2013-08-05 2015-02-26 Wobben Properties Gmbh Process for producing a composite molding, composite molding, sandwich component and rotor blade element and wind turbine
DE102014205803A1 (en) * 2014-03-28 2015-10-01 Bayerische Motoren Werke Aktiengesellschaft Apparatus and method for producing a fiber composite component with pure resin geometry arranged thereon
DE10155537B4 (en) * 2001-01-05 2016-02-11 Continental Teves Ag & Co. Ohg Method and injection mold for the production of motor vehicle sensors
FR3059934A1 (en) * 2016-12-14 2018-06-15 Safran Aircraft Engines A NEEDLE IMPREGNATION MOLD FOR PRODUCING A WORKPIECE FROM A WOVEN PREFORM
CN115256796A (en) * 2022-09-27 2022-11-01 四川纤谷塑业有限公司 A kind of molding process of basalt fiber composite material

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Publication number Priority date Publication date Assignee Title
WO2000056515A1 (en) * 1999-03-19 2000-09-28 Dag Thulin Apparatus for facilitating extraction of supply conduits for thermosetting resin from a mould cavity
DE10023208A1 (en) * 2000-05-12 2001-11-15 Alstom Power Nv Insulation of stator windings by injection molding
US6645416B2 (en) 2000-05-12 2003-11-11 Alstom Ltd. Insulation of stator windings by injection molding
DE10155537B4 (en) * 2001-01-05 2016-02-11 Continental Teves Ag & Co. Ohg Method and injection mold for the production of motor vehicle sensors
EP3150363A2 (en) 2013-08-05 2017-04-05 Wobben Properties GmbH Method for producing a composite moulding, composite moulding, sandwich component and rotor blade element and wind power plant
DE102013215384A1 (en) * 2013-08-05 2015-02-26 Wobben Properties Gmbh Process for producing a composite molding, composite molding, sandwich component and rotor blade element and wind turbine
EP3150363A3 (en) * 2013-08-05 2017-08-09 Wobben Properties GmbH Method for producing a composite moulding, composite moulding, sandwich component and rotor blade element and wind power plant
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DE102014205803A1 (en) * 2014-03-28 2015-10-01 Bayerische Motoren Werke Aktiengesellschaft Apparatus and method for producing a fiber composite component with pure resin geometry arranged thereon
FR3059934A1 (en) * 2016-12-14 2018-06-15 Safran Aircraft Engines A NEEDLE IMPREGNATION MOLD FOR PRODUCING A WORKPIECE FROM A WOVEN PREFORM
US11648740B2 (en) 2016-12-14 2023-05-16 Safran Aircraft Engines Impregnation mould having needles for producing a part from a woven preform
CN115256796A (en) * 2022-09-27 2022-11-01 四川纤谷塑业有限公司 A kind of molding process of basalt fiber composite material
CN115256796B (en) * 2022-09-27 2022-12-09 四川纤谷塑业有限公司 Forming process of basalt fiber composite material

Also Published As

Publication number Publication date
EP0686084A1 (en) 1995-12-13
SE9300639D0 (en) 1993-02-25
AU6159294A (en) 1994-09-14
SE9300639L (en) 1994-08-26
SE501085C2 (en) 1994-11-07

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