Single-piece propeller and method of making
A method for making a propeller product is disclosed. The propeller is formed using polyurethane cores adhered to a laminate hub to form a core assembly. An encapsulating structural laminate skin is then formed on the core assembly using a resin-transfer-molding process to create a single-piece composite propeller.
1. A method of making a propeller, said method comprising:
providing an already-cured composite propeller-shaped core, comprising:
providing an as-cured hub portion;
providing as-cured first and second blade portions; and
adhering the first and second blade portions to the hub portion to form the already-cured composite propeller shaped core;
introducing an uncured epoxy around the already-cured composite propeller-shaped core such that the core is at least partially encapsulated in the uncured epoxy; and
administering elevated temperatures to the uncured epoxy such that a substantially continuous covering is formed at a location where the propeller-shaped core transitions from the hub portion to one of the first blade portion or the second blade portion.
2. The method of claim 1 comprising: constructing said hub portion of the same material said first and second blade portions are constructed of.
3. The method of claim 2 comprising: constructing said hub portion of a first material which is more capable of withstanding compressive forces than is a second material used to construct said first and second blade portions.
4. The method of claim 3 comprising: selecting a polyurethane as said second material.
5. The method of claim 4 comprising: selecting an epoxy-based composite material as said first material.
6. The method of claim 1 , further comprising: enclosing said propeller-shaped core in a fibrous braid material before introducing the uncured epoxy.
7. The method of claim 1 wherein said administering step further comprises:
elevating temperature as a part of a resin-transfer-molding (RTM) process.
8. The method of claim 1 comprising: substantially immersing the already-cured composite propeller-shaped core in the uncured epoxy in the introducing step such that when the substantially continuous covering is formed in the administering step, the covering substantially encapsulates the core forming a single-piece propeller.
9. A method of fabricating a propeller, the method comprising:
providing a propeller-shaped foam core including a hub portion, a first blade portion and a second blade portion;
covering at least part of the foam core in a fibrous braid material by receiving the foam core within a sleeve of the fibrous braid material such that the fibrous braid covers the hub portion and at least a portion of each of the first and second blades;
placing the foam core in a mold;
saturating the fibrous braid material with uncured epoxy in the mold; and
curing the epoxy about the foam core to form a covering for the propeller.
10. The method of claim 9 comprising: forming the propeller-shaped foam core from separate first and second blade portions which are adhered about the hub portion.
11. The method of claim 9 comprising: drilling holes through the hub portion of the propeller to enable attachment to an aircraft.
12. The method of claim 9 comprising: covering and tacking the propeller-shaped foam core in the fibrous braid material before the saturating step.
13. The method of claim 12 , wherein an inner diameter of the fibrous braid material is greater than an inner diameter of any portion of the plurality of blade portions during said covering and wherein covering the propeller-shaped foam core in the fibrous braid material further comprises pulling opposing ends of the fibrous braid material from one another such that the fibrous braid material radially constricts onto the propeller-shaped foam core and substantially conforms to the external surface of at least a portion of the propeller-shaped foam core.