Modular mandrel for monolithic composite fuselage
A method of manufacturing a self-supporting, monolithic fuselage body, including engaging peripheral mandrel sections around at least one central mandrel section, placing uncured composite material on the mold surface, curing the composite material on the mold surface, and sliding the central mandrel section(s) out of engagement with the peripheral mandrel sections and disengaging the peripheral mandrel sections from the cured composite material without collapsing the mandrel sections. The peripheral mandrel sections each include a shape-retaining core of a thermally insulating material and an outer layer on an outer surface of the shape-retaining core. The outer layer has a coefficient of thermal expansion within the range of variation of that of the coefficient of thermal expansion of the composite material. A mandrel for layup and cure of a predetermined composite material in the manufacture of a monolithic fuselage is also discussed.
1. A method of manufacturing a self-supporting, monolithic fuselage body, the method comprising:
engaging a plurality of peripheral mandrel sections around a central mandrel section, the peripheral mandrel sections each including a shape-retaining core of a thermally insulating material and an outer layer on an outer surface of the shape-retaining core, the outer layer of the peripheral mandrel sections cooperating to define a mold surface;
placing uncured composite material on the mold surface to form a skin of the monolithic fuselage;
curing the composite material on the mold surface by heating the composite material in a pressurized atmosphere, a coefficient of thermal expansion of the composite material varying within a predetermined range during the cure, the outer layer of the peripheral mandrel sections having a coefficient of thermal expansion within the predetermined range;
after the composite material is cured, sliding the central mandrel section out of engagement with the peripheral mandrel sections along a direction substantially perpendicular to a portion of the mold surface without collapsing the central mandrel section;
disengaging the peripheral mandrel sections from the cured composite material without collapsing the peripheral mandrel sections, the cured composite material forming the fuselage body,
wherein the central mandrel section includes a shape-retaining core of the thermally insulating material and an outer layer surrounding the shape-retaining core, the outer layer of the central mandrel section defining a part of the mold surface.
2. The method according to claim 1 , wherein the peripheral mandrel sections are engaged around a single central mandrel section.
3. The method according to claim 1 , wherein placing the uncured composite material on the mold surface further includes forming a plurality of structural elements in contact with the uncured composite material that forms the skin of the monolithic fuselage, and wherein curing the composite material includes co-curing the skin and the structural elements.
4. The method according to claim 1 , further comprising placing a plurality of cured structural elements in contact with the uncured composite material that forms the skin of the monolithic fuselage, and wherein curing the composite material further includes co-bonding the skin and the structural elements.
5. The method according to claim 1 , wherein the outer layer of the peripheral mandrel sections has a coefficient of thermal expansion corresponding to that of the composite material.
6. The method according to claim 1 , wherein the outer layer of the peripheral mandrel sections and the composite material both include carbon fibers in an epoxy resin.
7. The method according to claim 1 , wherein the thermally insulating material has a thermal conductivity of less than 1 W/m° K.
8. The method according to claim 1 , wherein the thermally insulating material is carbon foam.
9. The method according to claim 1 , wherein the monolithic fuselage body includes at least 80% of a sum of parts forming a finished fuselage of a rotorcraft.