Process for the manufacture of polymer and composite products

Details Process for the manufacture of polymer and composite products Process for the manufacture of polymer and composite products

1997-11-18

2002-12-17

Staicovici, Stefan (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Direct application of fluid pressure differential to...

With internal application of fluid pressure

C264S136000, C264S137000, C264S250000, C264S257000, C264S266000, C264S267000, C264S271100, C264S279100, C264S294000, C264S322000, C264S324000, C264S325000, C156S245000

Reexamination Certificate

active

06495091

ABSTRACT:

The present invention relates to a process for the manufacture of polymer and/or composite products and to the related equipments.
BACKGROUND OF THE INVENTION
Polymers and polymer composites have the advantages of weight saving, high specific mechanical properties and good corrosion resistance which make them indispensable materials. Nevertheless, manufacturing costs are sometimes detrimental, since they can represent a considerable part of the total costs. Furthermore, the production of complex shaped parts is still a challenge for the composite industry. Parts with relatively simple geometries are common place today for composites; pre-peg manufacturing, autoclave, filament winding, pultrusion, etc. are examples of well-developed technologies. But the production of complex 3-dimensional parts usually requires injection moulding or compression moulding of short fibre composites (“engineering composites”). The drawback of short fibre reinforced composites is their considerable lower intrinsic specific mechanical properties. Assembly technologies used to obtain complex geometry for advanced composites are sometimes inefficient and not cost-effective.
The proper selection of a material system and process for manufacture of composite parts depends on a number of factors including material processability, design, part performance, and manufacturing economics [see in particular J.-A. E. M{dot over (a)}nson, New demands on manufacturing of composite materials, in High-performance composites, Ed. K. K. Chawla, P. K. Liaw, S. G. Fishman, TMS, Warrendale, Pa., (1994)].
As shown in
FIG. 1
, which shows a mapping of composite processing techniques with respect to their ability for complex shaping and annual production volumes, the number of parts to be produced and the required part size and complexity influence the selection of a suitable manufacturing process [see in particular W. J. Lee and J.-A. E. M{dot over (a)}nson, “Factors Influencing Process Selection and Processing” (Proceedings: Polymer Composite Applications for Motor Vehicles, SAE International, Detroit, USA, Feb. 25, 1991) 35.]. For low number of parts to be manufactured, a process which requires lower investment in tooling and equipment costs but longer cycle times and more labour may be favoured.
The limited potential for complex shape forming offered by advanced composite materials leaves little scope for design freedom in order to improve mechanical performance and/or integrate supplementary functions. This has been one of the primary limitation for a wider use of advanced composites in cost-sensitive large volume applications. Contrary to most traditional composite applications, many applications in, for example, the mechanical industry are small and are of more complex three-dimensional shapes, which are normally produced by casting techniques.
Traditional injection moulding, provides almost unlimited possibilities for shaping. Here, considerably greater design freedom for mechanical performance is achieved with a considerably cheaper material. However, the intrinsic mechanical properties are also lower, given the short fibre materials used, and so the potential for both load bearing and weight saving is diminished.
In most cases performance improvement has been achieved by the development of material systems with improved intrinsic properties (fibre types, resin systems and fibre content). These developments have also driven up raw material costs and the interest in branches with cost-sensitive applications has been reduced, slowing down the introduction of composite applications.
Increased design freedom nevertheless opens many possibilities for engineering solutions which may considerably increase the interest for composite materials in structural applications.
FIG. 2
gives an indication of this dilemma. Most of the manufacturing techniques used today for composite materials may be placed on the exponentially-shaped band as indicated in the diagram.
Given the demands of many industries today, it is obvious that. the desired direction for future development is towards the upper right-hand corner of the diagram. The development of material systems with both high intrinsic properties and improved formability for complex shapes may only be ensured by close interaction during the development of the material preforms and of the processing techniques.
In this view, several material systems and manufacturing techniques are today under development, aiming to improved complex shape forming of advanced composites under attractive manufacturing conditions. Novel material systems using either pre-impregnated preforms or post-shaping impregnation are being closely studied by several research groups [see in particular A. G. Gibson and J.-A. E. M{dot over (a)}nson, “Impregnation Technology for Thermoplastic Matrix Composites,” Journal of Composites Manufacturing, 3 (4) (1992), 223-233, F. Neil Cogswell, Thermoplastic Aromatic Polymer Composites (Oxford: Butterworth-Heinemann, 1992) and J.-A. E. M{dot over (a)}nson, “Processing of Thermoplastic-based Advanced Composites”, Advanced Thermoplastics and their Composites, ed. H-H. Kausch (Munich: Carl Hanser Verlag Gmbh. 1992), 273]. Powder preform techniques have so far been the most explored route to improved complex formability with thermoplastic-based composites, but automated tape placement methodologies have also shown promise [see in particular K. V. Steiner, E. Faude, R. C. Don and J. W. Gillespie Jr., “Cut and Refeed Mechanics for Thermoplastic Tape Placement,” (Proceedings of the 39th International SAMPE Symposium, Anaheim, Calif., 1994), 2627].
The potential conversion routes for composites, from fibre and matrix to finished products are illustrated on FIG.
4
. Traditionally each processing steps (
FIG. 3
) are developed by separate companies and semi-products delivered to the next link of the processing chain.
It is by no means clear that an optimal matrix material for a composite, in terms of fibre-matrix adhesion, is suited for the other demands set upon a composite part. For instance, environmental resistance and tribological performance may not always be given by a typical matrix material. Furthermore, a high fibre content will normally have a negative influence on the surface finish of the product. The free-forming potential of neat polymers or short fibre systems will always be superior to that of continuous fibre materials. In addition, a well-known strategy to reduce cost is to reduce the number of sub-components in complex structures while integrating multiple functionality. To meet several of these requirements with one material or one processing technique may not be possible.
Considering these points it is clear that higher flexibility of the composite materials is required in many applications to increase the material's attractiveness to design engineers. A more integrated approach using complementary materials and processes in the fabrication of the part would be desirable.
The logical step seemed therefore to integrate as far as possible the individual processing operations illustrated on FIG.
4
.
SUMMARY OF THE INVENTION
The aim of the present invention is to propose novel processing techniques and equipments permitting to remedy to the disadvantages of the existing techniques and in particular to reduce manufacturing costs by the suppression of intermediate processing and assembly stages.
Therefore, the invention concerns a novel processing technique where neat polymers, reinforcements and/or preforms and/or composites are combined in a single operation, by combining several processes into a single step or as a sequence of steps in rapid succession, where simultaneous material and process integration is achieved.
As shown in
FIG. 7
this integrated processing technique offers larger design freedom, performance integration and multifunctionality in complex shaped composite parts.
An object of the present invention is an integrated processing unit allowing an automated combination of processing steps such as

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