Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1996-12-05
1999-11-09
Aftergut, Jeff H.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156 91, 156250, 156264, B29B 1116, D04H 1800
Patent
active
059806699
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to manufacturing structural parts of complex shape out of composite material.
In well known manner, a method of manufacturing a part out of composite material comprises making a fiber reinforcement structure or "preform", and then densifying the preform with a matrix that fills the accessible pores of the preform, at least in part.
For example, the fiber preform is made from fibers that are in the form of felts, mats, threads, cables, twisted strands, yarns, . . . Threads or cables may be wound on reels, or disposed in unidirectional sheets, or woven to form sheets of woven cloth, braids, or three-dimensional woven structures.
The preform is given a shape that corresponds to that of the composite material part that is to be made. This can be done by winding filaments, from unidirectional elements, or by superposing plies that are stacked flat or wound or draped over a former. In which case, the superposed plies can be bonded together by implanting threads or by needling.
The preform can be densified using a liquid method or by chemical vapor infiltration.
The liquid method consists in impregnating the preform or in making it from pre-impregnated threads or plies, with the composition of the impregnation constituting a precursor of the matrix. The precursor, e.g. a resin, is generally transformed by heat treatment.
Chemical vapor infiltration is performed by placing the preform in an enclosure into which a gas is admitted containing at least one precursor of the matrix. Under the conditions, in particular of temperature and pressure, that are established within the enclosure, the gas diffuses into the preform within which a matrix-forming deposit is formed by decomposition of a gaseous precursor, or by a reaction between gaseous precursors, on coming into contact with the fibers of the preform.
The materials constituting the preform and the matrix are selected as a function of the application envisaged for the composite material part. For structural parts that are subjected in operation to high temperatures, it is advantageous to make use of thermostructural composite materials. Such materials are characterized by mechanical properties that make them suitable for constituting structural elements, and also by their ability to conserve such mechanical properties at high temperatures. By way of example, such materials comprise carbon--carbon or C--C composite materials (a carbon fiber preform densified by a carbon matrix), or ceramic matrix composite materials or CMCs (carbon or ceramic fiber preform densified with a ceramic matrix).
Making composite material structural parts of complex shape poses special problems. The term "complex shape" is used herein to designate a shape that it is difficult or impossible to obtain by simple operations of winding or of draping or stacking plies, i.e. shapes other than plane, parallelepipedal, cylindrical, or bodies of revolution.
One known technique for making composite material parts of complex shape consists in making components therefor which are simple in shape, and then in assembling the components together. However, that inevitably gives rise to discontinuities in the assembled parts, which can affect their mechanical properties. In addition, it is necessary to make use of assembly elements that are themselves made of composite material, in particular screw fasteners, and these are expensive to make.
To avoid the above drawbacks, at least in part, proposals have been made to assemble together a plurality of parts that are simple in shape while they are still in the form of preforms, prior to being densified. Assembly can be performed by juxtaposing preform portions and by holding them in place by means of tooling for densification purposes. The tooling can be removed after a consolidation stage, i.e. after an initial densification stage that is sufficient to bond the preform portions together so that the preform can be handled while still retaining its shape. The use of tooling gives rise to significant drawbacks. When densification is
REFERENCES:
patent: 4966802 (1990-10-01), Hertzberg
patent: 5112422 (1992-05-01), Takahashi
patent: 5114762 (1992-05-01), Bontems et al.
patent: 5310434 (1994-05-01), Vives et al.
Martin Guy
Maumus Jean-Pierre
Aftergut Jeff H.
Societe Nationale D'Etude et de Construction de Moteurs D'Aviati
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