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)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20389036

Family Applications (1)

Country Status (4)

Cited By (7)

Citations (6)

• 1993
  • 1993-02-25 SE SE9300639A patent/SE501085C2/sv unknown
• 1994
  • 1994-02-18 EP EP94908546A patent/EP0686084A1/en not_active Ceased
  • 1994-02-18 WO PCT/SE1994/000136 patent/WO1994019176A1/en not_active Application Discontinuation
  • 1994-02-18 AU AU61592/94A patent/AU6159294A/en not_active Abandoned

Patent Citations (6)

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