Multi-piece mandrel for building up airfoil structure
A mandrel includes a mandrel body upon which to build ceramic matrix composite (“CMC”) yarns to provide a shear tube for building up an airfoil from CMC fabric layers. The mandrel body formed of at least two mandrel parts interfitting to define a desired shape for the shear tube, and such that after formation of the airfoil the at least two parts of the mandrel body can be separately removed from the shear tube in order to facilitate removal. A method is also disclosed.
1 . A method of forming a gas turbine engine component having a airfoil including the steps of:
providing a mandrel formed of at least two mandrel parts, with interfitting structure to hold the at least two mandrel parts together;
forming a shear tube on an outer surface of the at least two parts of the mandrel by placing a ceramic matrix composite (“CMC”) yarn on the outer surface of the at least two mandrel parts;
forming additional CMC fabric layers on the shear tube to form the airfoil;
beginning densifying the CMC fabric layers and yarn;
removing one of the at least two mandrel parts; and
then removing an other of the at least two mandrel parts.
2 . The method as set forth in claim 1 , wherein a first of the at least two mandrel parts has a bowed profile such that a central portion is spaced closer to a second of the at least two mandrel parts than are upper and lower areas of the first mandrel part, and the second mandrel part has an outer shape which is closer to straight, and the second mandrel part being the one initially removed from the shear tube, and the first mandrel part then moved away from a bowed surface on an inner periphery of the shear tube, and the first mandrel part then being the other removed part.
3 . The method as set forth in claim 2 , wherein the mandrel has grooves on an outer surface to facilitate movement of gas during the densification step of the CMC yarn and fabric layers.
4 . The method as set forth in claim 2 , wherein the interfitting structure between is that the first and second mandrel parts have a tongue and groove connection.
5 . The method as set forth in claim 2 , wherein edges of each of the first and second mandrel parts are formed with chamfers to allow turning of the one of the at least two mandrel parts relative to the other to facilitate removal of the second mandrel part.
6 . The method as set forth in claim 1 , wherein the mandrel has grooves on the outer surface to facilitate movement of gas during the densification step of the CMC yarn and fabric layers.
7 . The method as set forth in claim 1 , wherein the interfitting structure is that the at least two mandrel parts have a tongue and groove connection.
8 . The method as set forth in claim 7 , wherein edges of each of the at least two mandrel parts are formed with chamfers to allow turning of the one of the at least two mandrel parts relative to the other to facilitate removal of the one of the at least two mandrel parts.