FIELD OF THE INVENTION

The present invention is directed to hollow ceramic matrix composite (CMC) articles, mandrels for forming hollow CMC articles, and methods for forming hollow CMC articles. More particularly, the present invention is directed to hollow CMC articles, mandrels for forming hollow CMC articles, and methods for forming hollow CMC articles including a curve having a single turning point.

BACKGROUND OF THE INVENTION

Gas turbines are continuously being modified to provide increased efficiency and performance. These modifications include the ability to operate at higher temperatures and under harsher conditions, which often requires material modifications and/or coatings to protect components from such temperatures and conditions. As more modifications are introduced, additional challenges are realized.

One modification to increase performance and efficiency involves forming gas turbine components, such as, but not limited to, airfoils, buckets (blades), nozzles (vanes), combustion liners, and shrouds from CMC. However, CMC materials may be more susceptible to bending stresses and deformation than other structural materials such as superalloys. Therefore, for components which include hollow spaces, a wrap layer of CMC may be incorporated in order to stabilize the structure surrounding the hollow spaces. However, the CMC plies of the wrap layer may be susceptible to fraying prior to densification, particularly at each turning point of the CMC plies about the hollow spaces.

BRIEF DESCRIPTION OF THE INVENTION

In an exemplary embodiment, a hollow CMC article includes a ply-wrap layer defining a cavity disposed within the ply-wrap layer. The ply-wrap layer includes a first face, a second face, a root portion bridging the first face and the second face, and a plurality of CMC wrap plies. The root portion defines a terminus of the ply-wrap layer including a cross-sectional conformation, and the cross-sectional conformation consists of a curve having a single turning point. Each of the plurality of CMC wrap plies is disposed along the first face, wrap over the root portion, and extend along the second face. The hollow article further includes a plurality of CMC lateral plies disposed along at least one of the first face and the second face.

In another exemplary embodiment, a ply-support mandrel for forming a hollow CMC article includes a first face support, a second face support, and a root portion support bridging the first face support and the second face support. The root portion support defines a mandrel terminus, and includes a cross-sectional conformation. The cross-sectional conformation consists of a curve having a single turning point.

In another exemplary embodiment, a method for forming a hollow CMC article includes applying a plurality of CMC wrap plies to a ply-support mandrel. Applying the plurality of CMC wrap plies includes wrapping each of the plurality of CMC wrap plies along a first face support and a second face support of the mandrel and over a root portion support of the mandrel bridging the first face support and the second face support, and forming a ply-wrap layer supported on the mandrel. The ply-wrap layer includes a first face, a second face, and a root portion bridging the first face and the second face. The root portion support includes a cross-sectional conformation consisting of a curve having a single turning point. A plurality of CMC lateral plies is applied along at least one of the first face and the second face. The plurality of CMC wrap plies and the plurality of CMC lateral plies are consolidated, pyrolized, and densified. The mandrel is removed, forming a cavity disposed within the ply-wrap layer.

Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

