Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1998-11-13
2000-10-24
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264 405, 264257, 425145, 425149, 700 50, B29C 4576
Patent
active
061362360
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical field
The invention concerns a manufacturing process for composite material parts, using the resin transfer moulding technique, otherwise known as RTM.
More precisely, the process of the invention is designed to manufacture large composite material parts on an industrial scale, with a high fibre content, which is to say over 58%.
This objective makes the process of the invention particularly attractive for the aviation industry. Consequently, parts manufactured using this process may be used in the construction of aeroplanes, helicopters, launchers, missiles, etc.
2. State of the Technique
The aviation industry has used composite materials for a number of years now. These materials allow, in particular, significant reductions in weight to be made whilst providing rigidity and mechanical properties that are comparable to those of metal parts.
Given this background, various techniques are used, depending on the nature and dimensions of the part to be manufactured. Amongst these techniques, we can especially mention filament winding, injection and stamping of thermoplastic materials and above all the autoclave moulding of textiles pre-impregnated with thermosetting resin.
In the particular case of the production of large parts such as the aerofoil or fuselage, the mechanical stresses specific to the aviation field make a high fibre content necessary, which is to say over 58%. In the current status of the technique, such material composite parts are made from textile that is pre-impregnated with thermosetting resin. The manufacturing process consists of draping the textiles onto a shape then compressing the textiles by covering them with a sealed vessel in which a vacuum is created. The assembly is then placed in an autoclave where it undergoes a heat treatment cycle to polymerise the resin.
In other fields such as the automobile industry, capital goods industry, etc., the resin transfer moulding, or RTM, technique, has been used for a lot of years to manufacture parts with a relatively low fibre content, which is to say less than 54%. This moulding technique consists of inserting a dry, fibre pellet into a mould, then injecting a liquid organic resin into the mould in a vacuum and at low pressure, so that the pellet is impregnated. Heating the resin-impregnated pellet polymerises the resin before it is removed from the mould.
At present, this RTM technique is relatively well controlled for the production of parts with a low fibre content, which is to say with a fibre content of less than 54%.
In comparison with other techniques which use composite materials, the RTM technique has many advantages, such as the reduction in the overall implementation time involved, the low level of investment for the production system (no chilling system or autoclave), the high dimensional accuracy of the parts produced, especially in terms of thickness, the very good surface finish, the exceptionally good health and safety conditions, etc.
However, when parts with a high fibre content are to be produced, which is to say with a fibre content of more than 58%, as demanded by the aviation and space industries for example, the resin must be injected into the mould containing the dry fibre pellet when the pellet is strongly compressed. Within its known implementation procedures, the RTM technique does not allow large parts to be produced with this degree of compression.
In fact, the high loss of load introduced by the highly compressed textile fibres of the pellet slows the resin's penetration into it.
Furthermore, the pressure at which the resin is injected must remain sufficiently low so that the direction of the textile fibres is not altered during injection. It is known that the mechanical properties of the part produced are essentially defined by the direction of the textile fibres in the resin matrix.
Consequently, when the volume of the part to be produced increases, the time required for the resin to penetrate the entire mould exceeds the time required for the resin to start polymerising (usually ca
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Boccard Alexis
Chevassus Nicolas
Aerospatiale - Societe Nationale Industrielle
Silbaugh Jan H.
Staicovici Stefan
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