Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-03-26
2004-07-27
Weisberger, Rich (Department: 3624)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C156S148000, C156S149000, C028S107000, C028S114000, C028S206000, C028S206000, C028S206000, C442S273000, C442S319000, C442S406000
Reexamination Certificate
active
06767602
ABSTRACT:
The present invention relates to manufacturing brake disks out of composite material, and in particular to preparing fiber preforms for such manufacture. The field of application of the invention is more particularly that of brake disks made of thermostructural composite material. Thermostructural composite materials for brake disks are typically carbon-carbon or “C—C” composites constituted by a reinforcing preform of carbon fibers densified by a carbon matrix and optionally subjected to final siliciding treatment. Other suitable composite materials are ceramic matrix composites or “CMCs” constituted by a reinforcing preform of refractory fibers (carbon or ceramic) densified by a ceramic matrix, e.g. carbon-silicon carbide or “C—SiC” composites.
The use of thermostructural composite materials, in particular C—C composites, for making brake disks is well known, in particular for the multi-disk brakes of airplanes, and also for land vehicles, e.g. F1 racing cars.
The usual technique for manufacturing such disks consists in making annular fiber preforms and in densifying them with a matrix of carbon that fills the pores of the preforms.
The preforms are usually made by superposing layers of fiber fabric which are bonded together, in particular by needling, so as to give the preform the cohesion it requires to avoid any risk of a disk delaminating while it is in use. The fiber fabric layers are typically multidirectional two-dimensional layers formed at least in part out of continuous filaments, e.g. layers made by weaving or braiding or knitting threads made up of continuous or discontinuous fibers, or layers made up of a plurality of sheets of unidirectional cables disposed in different directions and bonded together by light needling. Fiber webs or layers of felt can be added to provide discontinuous fibers that are easily taken by the needles during needling to provide Z-direction bonding between layers (i.e. transversely relative to the faces of the layers). These fiber webs or felt layers also serve to recycle the fiber scrap that is produced when cutting the fiber fabric layers as is necessary to obtain annular preforms.
The use of fiber webs or felts made from such scrap material is described in particular in documents FR-A-2 626 294 and EP-A-0 530 741. According to the latter document, the layers of felt can be interleaved between the layers of fiber fabric in the core of a preform, or they can be added to the faces of the core in order to constitute surface layers of a preform that are designed to be eliminated in machining operations that take place during and/or after densification.
Preforms can be densified by chemical vapor infiltration or by using a liquid, both of which techniques are well known. Chemical vapor infiltration consists in placing the preforms that are to be densified in an enclosure into which a matrix-precursor gas is admitted that, under controlled conditions of temperature and pressure, diffuses within the preform and forms a deposit of matrix material on the fibers by reaction between its own components or by decomposition. When deposition takes place preferentially in the surface pores of the preform, tending to close them prematurely, it can be necessary to proceed with one or more intermediate surface-machining or “descaling” operations in order to recover surface pores and allow densification to proceed to the core of each preform.
Densification by means of a liquid consists in impregnating a preform with a matrix precursor in the liquid state, e.g. a resin, and then transforming the precursor, generally by heat treatment. Several consecutive impregnation cycles can be necessary in order to achieve the desired degree of densification. It is also possible to combine the techniques of chemical vapor infiltration and of liquid impregnation.
Compared with metal disks, brake disks made of thermostructural composite material, and in particular of C—C composite material, provide a considerable saving in mass while providing excellent tribological properties and low wear. They are also well adapted to the severe conditions of use encountered in airplanes and in F1 racing cars.
Extending the use of thermostructural composite brake disks to other types of vehicle, such as trains, heavy trucks, coaches, utility vehicles, or private cars is being slowed down specifically because of particular problems encountered in such use.
Thus, tests performed by the Applicant on a top-of-range private car with C—C composite brake disks made using a method analogous to that used for manufacturing airplane brake disks have demonstrated that they can sometimes give rise to undesirable vibration, and to braking torque that can be irregular. In those brake disks, the preforms were made by needling together layers of base texture, which texture was made up of a plurality of unidirectional sheets of cables disposed at different angles (e.g. three sheets at 0°, +60°, and −60° C.) that were themselves preneedled together. It is likely that the use of that base fabric gives rise to irregular wear of the friction faces of the disks that come into contact with the brake pads, which phenomenon gets worse over the lifetime of the brake disks and generates vibration.
An object of the present invention is to provide a method of preparing fiber preforms that enables brake disks to be made out of composite material that do not present those drawbacks.
A particular object of the present invention is to provide such a method enabling brake disks to be made of composite material that are suitable for use on industrial or private motor vehicles without generating undesirable vibration and regardless of braking conditions, while also delivering braking torque that is regular and without any wear that is abnormally fast.
Another object of the present invention is to obtain such performance at a cost price that is compatible with the brake disks being used in mass-produced industrial or private motor vehicles.
Such objects can be achieved by a method of the type comprising superposing and bonding together fiber layers comprising structural layers formed at least in part out of continuous filaments and out of at least one felt layer, in which method structural fiber layers are used to form at least a first preform portion that is to constitute the fiber reinforcement of the core of the brake disk, while the or each preform portion that is to constitute the fiber reinforcement of a friction portion of the brake disk is constituted by a felt, at least in its portion adjacent to the friction face.
The term “structural fiber layer formed at least in part out of continuous filaments” is used herein to mean a layer that is woven, braided, or knitted out of continuous threads, themselves made of continuous or discontinuous fibers, or a layer constituted by a sheet of unidirectional, continuous cables, twisted strands, or threads, the cables, strands, or threads, themselves being constituted by continuous or discontinuous fibers, or else a layer constituted by a plurality of such sheets superposed in different directions and bonded together, e.g. by preneedling, or indeed such a fiber layer associated with a thin web of fibers to which it is bonded, e.g. by light needling. Such structural fiber layers are used to constitute a preform portion that is suitable for conferring to the core of the brake disks the mechanical properties which are required for transmitting braking forces without rupturing or damaging the disks, in particular where the core is mechanically linked to the member with which the disk is bound in rotation. The structural fiber layers can be placed flat, parallel to the faces of the disks, or they can be wound around the axis of the disks. If they are wound, the portion of the preform corresponding to the core of the disk can be obtained by cutting slices from a sleeve obtained by rolling up a strip of structural fiber fabric on a mandrel to form layers that are superposed on one another.
The felt forming, at least a part of the or each portion of the preform that is to
Duval Renaud
Lherm Eric
Messier-Bugatti
Weingarten Schurgin, Gagnebin & Lebovici LLP
Weisberger Rich
LandOfFree
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