High temperature wet filament winding arrangement

Abstract: In the embodiment described in the specification, a high temperature wet filament winding arrangement has a wet bath (20) containing a resin at a temperature above 500°F and filaments drawn from a spool rack are passed through the wet bath (20) and then through a heated comb (16) which maintains the temperature of the filaments (14) above 500°F, after which the filaments are passed through a heated passage controlled to maintain the temperature above 500°F. A winding eye (26), also heated to maintain the filament temperature above 500°F, directs the heated fibers (14) onto a mandrel (30) where they are wound in uniform layers into the form of a final product. A mandrel heater (32) heats the mandrel (30) to which the fibers are being applied so as to maintain a uniform temperature above 500°F.

Description: This invention relates to wet filament winding arrangements for manufacturing composite products. The wet filament winding process is a process in which a reinforcing fiber for a manufactured product is wetted with a molten or a liquid resin by passing the fiber through a liquid resin bath and then delivering it to a rotating mandrel in the wetted state. The wetted fiber is then placed precisely on and held in intimate contact with previously delivered wetted fibers so that when the winding process is complete the part has a very precisely controlled fiber arrangement and uniform fiber-to-resin ratio, producing a part that is constant in composition throughout its volume. The wet resin is then solidified in the manner required by the particular resin, i.e. by cooling a resin that is thermoplastic below its solidification temperature or by setting a settable resin using pressure, heat, ultraviolet light, or a curing agent, if necessary. Wet filament winding processes have been used to fabricate composite tubing, pressure vessels, and parts having varying cross-sectional areas as well as similar structures and, for specific structural arrangements, wet filament winding can accommodate the insertion of other materials in particular regions of the part such as the ends or intermediate sections. Conventional wet filament winding processes, however, have not been capable of using resins that require temperatures of at least 500°F to be maintained throughout the entire wet stage of the fabrication process because the resin cools quickly after leaving the liquid resin bath. Processes for coating fibers with liquid or molten resin to provide a resin reinforced fiber structure which is formed into a continuous fiber reinforced structure having a desired cross-sectional configuration are disclosed in Patents Nos. 4,168,194, 4,154,634, Re 30,770 and 4,285,749. The arrangements described in those patents, however, would not permit precise placement of wetted fiber on a mandrel as is required for wet filament winding. Patent No. 5,529,652 discloses the manufacture of fiber reinforced thermoplastic "pre-pregs" consisting of fibers which have been preimpregnated with resins and then solidified so that the product can be stored for later use in the manufacture of end products. Patent No. 5,096,645 describes the fabrication of extruded thermoplastic members that are reinforced by longitudinally extending prestressed elements which are fiber reinforced thermosetting resins that are partially cured in cylindrical dies. The prestressed elements are put in tension and encased in thermoplastic by an extrusion process to produce a solid final product. Patent No. 5,098,496 describes a process for making a postformable composite article containing a heat curable thermosetting polymer by introducing reinforcing fibers continuously into a heat hardenable thermosetting resin and then pulling the polymer composition fiber mixture continuously through a die having a desired shape to form the composite into a continuous product of desired cross-sectional configuration by controlling the pull rate and the die temperature. The polymer composition-fiber mixture is maintained in a gel state so that the formed article can then be cured in a different shape. Patent No. 5,425,829 discloses a conventional wet filament winding process for forming composite leaf springs containing glass fibers with a reduced spring rate and uniform stress by replacing a proportion of the glass fibers with plastic fibers. Patent No. 4,975,232 describes a process for manufacturing fiber-reinforced linear plastic material formed with a twisted groove on the outer surface to allow for accommodation of an optical fiber by heating a fully cured resin above its glass transition temperature and then inducing a twisted groove. Japanese Patent Abstract 02 220828 discloses a filament winding forming method, which discloses the steps of heating a bath of resin and passing the filament over a series of wheels to an eye which guides the filament on to a mandrel. The mandrel is then placed in an oven. EP-A-0 463 611 discloses a process involving pre-impregnated filaments. The pre-impregnated filaments are heated to a temperature within 10°C of their melt temperature to make them more flexible. The pre-impregnated filaments are then wound on to a mandrel. WO 99/12716 discloses a process and arrangement for producing a hollow body of fibre reinforced thermoplastic. A continuous fibre bundle is impregnated with a thermoplastic at a temperature at which the thermoplastic is molten and has a low viscosity. The bundle is then passed on to a heated press, maintained at the same temperature as the impregnation stage. The impregnated fibre is then cooled so that the thermoplastic is viscous during application to a core-moulding tool, which is situated in an oven. A problem observed with the prior wet filament winding arrangements for manufacturing composite products is obtaining a uniform resin/filament ratio throughout the volume of the product. According to the present invention, there is provided a high temperature wet filament winding arrangement for producing a composite product, the arrangement comprising a filament supply for supplying at least one filament, a wet bath, means for guiding the at least one filament through said wet bath, a mandrel on which the wetted filament is to be wound in a predetermined shape and an eye for guiding the wetted filament on to said mandrel, characterised in that the wet bath is maintained at a temperature above 260°C (500°F), the arrangement further comprising a heated enclosure for conveying the at least one wetted filament from the wet bath at a temperature above 260°C (500°F), and wherein said eye is heated and heating means is provided for heating at least the portion of the mandrel to which the wetted filaments are supplied by said eye to maintain the filaments at above 260°C (500°F). Preferably, the high temperature wet filament winding arrangement further comprises a heater for the eye to maintain the temperature of the at least one wetted filament passing through the eye at above 260°C (500°F). Advantageously, the high temperature wet filament winding arrangement further comprises a heated comb for guiding wetted filament from the wet bath to the heated passage and maintaining the temperature of the at least one wetted filament above 260°C (500°F). The present invention also provides a method for producing a composite product using a high temperature wet filament winding arrangement, the method comprising the steps of drawing at least one filament from a filament supply through a wet bath to produce a wetted filament, and guiding the at least one wetted filament on to a rotating mandrel in a predetermined shape using an eye, characterised in that the wet bath is maintained at a temperature above 260°C (500°F), the at least one wetted filament is conveyed through a heated enclosure from the wet bath at a temperature above 260°C (500°F), and through said eye which is heated and on to a heated portion of said mandrel maintaining the wetted filaments at above 260°C (500°F). Preferably, the method further comprises the step of passing the at least one wetted filament through a heated comb, said comb for guiding the at least one wetted filament from the wet bath to the heated passage and maintaining the temperature of the at least one wetted filament above 260°C (500°F). BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the invention will be apparent from a reading of the following description in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic plan view illustrating a representative embodiment of a high temperature wet filament winding arrangement for a composite part manufactured in accordance with the invention; and Fig. 2 is a side view of the arrangement shown in Fig. 1. DESCRIPTION OF PREFERRED EMBODIMENTS In the typical embodiment of the invention illustrated in the drawings, a wet filament winding system 10 has a stack of fiber spools 12 from which fibers 14 are pulled through a comb 16 and directed through a fiber impregnation assembly 18 which draws the fibers downwardly into a high temperature wet bath 20 in which the fibers are coated and impregnated with a resin maintained at a high temperature above 500°F. The fibers are then drawn through a heated outlet comb 22 with an independent temperature control, assuring maintenance of above 500°F, and are then passed through a heated enclosure 24 which also has an independent temperature control and maintains the temperature of the resin coated on the fibers at a level above 500°F. From the heated enclosure 24, the fibers are passed in the form of a band through a heated placement eye 26 which also has an individually controlled heater 28 to maintain the temperature of the wetted tow band above 500°F as it passes to a mandrel 30 on which it is wound by oscillating motion of the placement eye 26 as the mandrel rotates so as to provide uniform layers of filament on the mandrel. A separate heating arrangement 32 is provided to heat the mandrel assuring placement of the tow band on a heated region so that the temperature of the adjacent portion of the fibers previously wound on the mandrel is maintained at a temperature of at least 500°F. The resin in the high temperature wet bath 20 may be any resin, whether thermoplastic or otherwise, which can be maintained at a temperature above 500°F without degradation and which can be cured or solidified conveniently either by cooling or by curing with pressure, heat, ultraviolet light or the like. By maintaining the entire wet filament winding system from the wet bath 20 to the mandrel 30 at a temperature above 500°F, it has been found that the uniformity of coating of the fibers and resin on a mandrel is substantially improved compared with conventional wet filament winding systems for composite manufacture. In such conventional systems, partial solidification of the filaments previously wound on the mandrel is interrupted by application of an overlying wet filament at a higher temperature, producing irregularities in the final product. Moreover, solidification of the resin on the filament can occur prior to winding on the mandrel, likewise producing irregularities in the finished product and possible gaps in the resin layers provided by the winding. Moreover, if a resin has partially solidified or cured before winding, it is subject to settling in the product after winding, resulting in deformation of the product. This is avoided in accordance with the invention by maintaining the wet filaments at a temperature in excess of 500°F both prior to and during the winding of the mandrel until the winding has been completed and then solidifying the resin uniformly on the mandrel. Although the invention has been described herein with reference to specific embodiments, many modifications and variations therein would readily occur to those skilled in the art. Accordingly, all such variations and modifications are included within the intended scope of the invention.

Claims: A high temperature wet filament winding arrangement for producing a composite product, the arrangement comprising a filament supply (12) for supplying at least one filament, a wet bath (20), means for guiding the at least one filament through said wet bath, a mandrel (30) on which the wetted filament is to be wound in a predetermined shape and an eye (26) for guiding the wetted filament on to said mandrel (30), characterised in that the wet bath (20) is maintained at a temperature above 260°C (500°F), the arrangement further comprising a heated enclosure (24) for conveying the at least one wetted filament from the wet bath (20) at a temperature above 260°C (500°F), and wherein said eye (26) is heated and heating means (32) is provided for heating at least the portion of the mandrel (30) to which the wetted filaments are supplied by said eye (26) to maintain the filaments at above 260°C (500°F). A high temperature wet filament winding arrangement as claimed in Claim 1, further comprising a heater (28) for the eye (26) to maintain the temperature of the at least one wetted filament passing through the eye at above 260°C (500°F). A high temperature wet filament winding arrangement as claimed in Claim 1 or 2, further comprising a heated comb (22) for guiding wetted filament from the wet bath (20) to the heated passage (24) and maintaining the temperature of the at least one wetted filament above 260°C (500°F). A method for producing a composite product using a high temperature wet filament winding arrangement, the method comprising the steps of drawing at least one filament from a filament supply through a wet bath to produce a wetted filament, and guiding the at least one wetted filament on to a rotating mandrel in a predetermined shape using an eye, characterised in that the wet bath is maintained at a temperature above 260°C (500°F), the at least one wetted filament is conveyed through a heated enclosure from the wet bath at a temperature above 260°C (500°F), and through said eye which is heated and on to a heated portion of said mandrel maintaining the wetted filaments at above 260°C (500°F). A method as claimed in Claim 4, further comprising the step of passing the at least one wetted filament through a heated comb, said comb for guiding the at least one wetted filament from the wet bath to the heated passage and maintaining the temperature of the at least one wetted filament above 260°C (500°F).

Inventors: SMITH MITCHELL D, VAN DINE PIETER, SMITH, MITCHELL D., VAN DINE, PIETER
Applicants: ELECTRIC BOAT CORP, ELECTRIC BOAT CORPORATION
Application year: 1999
Main classification: B29C53
IPC codes: B29C53, B21F99