Textiles: manufacturing – Textile product fabrication or treatment – Of thread interlaced article or fabric
Patent
1997-12-17
1999-11-30
Vanatta, Amy B.
Textiles: manufacturing
Textile product fabrication or treatment
Of thread interlaced article or fabric
28143, 28110, 28114, 28170, D04H 1300
Patent
active
059919876
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTIONS
The invention relates to methods and to apparatuses for producing annular parts of composite material and preforms for such parts, and also to the parts and to the preforms themselves. More particularly, the invention relates to methods and apparatus for producing preforms by winding a fibrous strip on a mandrel, the wound layer assembly being intended to be cut into rings either before or after densification by a matrix.
Conventional methods of producing preforms for composite material parts consist in stacking flat layers of fibrous material, cutting or machining the assembly to obtain a preform with the desired shape, and then densifying the preform. When the part to be produced is a brake disk or some other annular part, about half of the weight of the material is lost when producing annular preforms from an assembly of stacked layers.
A number of proposals have been put forward to reduce such waste. One proposal consists in assembling an annular preform to be densified from layers of fibrous material each in the form of juxtaposed sectors, the layers then being stacked. Such a method reduces waste but does not avoid it.
A further proposal made in French patent application FR-A-2 506 672 is described below with reference to FIGS. 1A to 1D. Annular or cylindrical elements are produced by winding a fibrous strip on a cylindrical mandrel (FIG. 1A) to produce a cylindrical sleeve (FIG. 1B). During winding, the superposed layers are connected together by needling. The cylindrical sleeve can be cut perpendicularly to its axis to obtain annular preforms to be densified (FIG. 1C).
A method similar to the above has also been described in French patent application FR-A-2 584 107.
That method avoids wasting material, but the parts made from preforms produced by that method have disadvantageous features which come to light during service. Brake disks are subjected to shear stresses in a tangential direction during use. The stresses are particularly high in the notches formed in the inner or outer border (FIG. 1D) to connect the disk with a moving or a fixed portion. Such shear stresses E can cause the part to delaminate, i.e., it is destroyed by the layers in the preform separating.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a method and apparatus for producing preforms for annular parts of composite material which have a high resistance to delamination, and which limit the loss of material caused by carrying out the method.
In the method and apparatus of the invention, a strip of fibrous material is wound around an elliptical mandrel to form an elliptical sleeve. The elliptical sleeve can be cut obliquely to produce annular preforms for densification or it can itself act as the preform for densification, cutting being delayed until the end of one or more of the densification steps. The cutting plane is inclined to the right cross section of the elliptical sleeve, i.e. the cutting plane is not perpendicular to the sleeve axis. The inner and outer portions of the cut rings are machined to obtain circular elements.
The method and apparatus described above exploit the fact that the projection of an ellipse onto a plane passing through its major axis and at an angle .alpha. to the plane of the ellipse is a circle of diameter equal to the major axis of the ellipse. The angle a can be calculated using the following formula:
The principle of this aspect of the invention is illustrated in FIGS. 2A to 2D.
FIG. 2A shows a strip of fibrous material being wound around an elliptical mandrel and FIG. 2B shows the cutting plane of the elliptical sleeve produced by the sleeve produced by the assembly of superposed layers. In this example, the ring cut from the sleeve is perfectly circular at its half-width, but elliptical at the inner and outer peripheries. The cutting plane can also be selected so that the ring is circular at its inner or outer periphery or at another distance from the peripheries of the ring. (In theory, a cutting plane could be selected which would render th
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Coupe Dominique
Jouin Jean-Marie
Olry Pierre
Societe Nationale D'Etude et de Construction de Moteurs D'Aviati
Vanatta Amy B.
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