# US 2019/0315451 A1 · Propeller blade spar > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0315451 A1 - Document ID: US20190315451A1 - Status: Published application - Kind: A1 - Application number: 16/384,079 - Filed: 2019-04-15 - Published: 2019-10-17 - Earliest claimed: 2018-04-17 - Assignees: Ratier-Figeac SAS - Applicants: Ratier-Figeac SAS - Inventors: Bruno Seminel; Stanislas Tutaj - Web page: https://patentgrep.com/patent/US20190315451A1 ## CPC - B29C 70/48: and impregnating the reinforcements in the closed mould, e.g. resin transfer moulding [RTM] {, e.g. by vacuum} - B64C 11/20: Constructional features - B29C 70/446: {Moulding structures having an axis of symmetry or at least one channel, e.g. tubular structures, frames} - B29D 99/0025: {Producing blades or the like, e.g. blades for turbines, propellers, or wings} - B29D 99/0028: {hollow blades} - B64C 3/185: {Spars} - F01D 5/147: {Construction, i.e. structural features, e.g. of weight-saving hollow blades (F01D5/148, F01D5/16 and F01D5/20 take precedence; blade shape F01D5/141; blades with cooling or heating channels or cavities F01D5/18; heating, heat-insulating or cooling means on blades F01D5/18)} - B29K 2063/00: Use of {EP, i.e.} epoxy resins {or derivatives thereof}, as moulding material - B29K 2105/089: {fabric} - F05D 2230/31: Layer deposition - B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00) - B64C: AEROPLANES; HELICOPTERS - B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00) - F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D) - B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS ## Abstract A method of manufacturing a spar for a propeller blade comprises forming a hollow inner core from a composite material, and then braiding carbon fibres around the inner core to form an outer spar structure. The hollow inner core may be formed using an inflatable bladder and a mould defining an outer shape of the spar. This construction avoids the need for a foam core to be provided within the spar. ## Claims ### Claim 1 A method of manufacturing a spar for an airfoil, comprising: forming an inner spar structure comprising a rigid body formed around at least one inflatable bladder or a removable core and mounted to an airfoil root, the rigid body being formed from a composite material; and forming an outer spar structure about the inner spar structure, the outer spar structure being formed from a composite material. ### Claim 2 (depends on 1) A method according to claim 1, wherein forming the inner spar structure comprises applying a plurality of fibres around the at least one inflatable bladder or the removable core, wherein the fibres are applied as fabric sheets. ### Claim 3 (depends on 1) A method according to claim 1, wherein forming the inner spar structure comprises applying a first layer of fibres, applying a structural core outside of the first layer of fibres, and applying a second layer of fibres outside of the structural core, such that a wall of the inner spar structure has a sandwich construction. ### Claim 4 (depends on 1) A method according to claim 1, wherein the rigid body is formed using a mould defining a shape of the inner spar structure. ### Claim 5 (depends on 1) A method according to claim 1, wherein the composite material of the rigid body has been only partially cured when forming the outer spar structure. ### Claim 6 (depends on 1) A method according to claim 1, wherein forming the outer spar structure comprises braiding a plurality of fibres around the inner spar structure. ### Claim 7 (depends on 1) A method according to claim 1, wherein the rigid body is formed around at least one inflatable bladder. ### Claim 8 (depends on 6) A method according to claim 6, wherein the rigid body is formed around a removable core, which is formed from a chemically destructible material. ### Claim 9 (depends on 8) A method according to claim 8, wherein the airfoil root comprises a through-hole to permit removal of the removable core from the rigid body. ### Claim 10 (depends on 1) A method according to claim 1, wherein forming the inner spar structure comprises forming one or more reinforcement members internal to the rigid body, wherein the reinforcement members are formed from the same composite material as the rigid body and are formed integrally with the rigid body. ### Claim 11 (depends on 10) A method according to claim 10, wherein the at least one inflatable bladder or the removable core comprises a first, axially-extending portion on a first side of at least one of the reinforcement members and a second axially-extending portion on a second side of the at least one of the reinforcement members, the first and second portions being configured to engage with one another around at least one of the reinforcement members. ### Claim 12 (depends on 1) A method of manufacturing an airfoil comprising: manufacturing a spar according to claim 1; attaching one or more airfoil forms to the spar; and forming an airfoil surface from a composite material around the spar and the one or more airfoil forms. ### Claim 13 A spar for an airfoil, comprising: an inner spar structure having a rigid body mounted to an airfoil root, the rigid body being formed from a composite material, and the rigid body defining a hollow internal cavity or an internal cavity filled by at least one inflatable bladder or a removable core; and an outer spar structure formed about the inner spar structure, the outer spar structure being formed from a composite material. ### Claim 14 (depends on 13) A spar according to claim 13, wherein the inner spar structure comprises one or reinforcement members internal to the rigid body, the reinforcement members being integral with the rigid body. ### Claim 15 (depends on 13) An airfoil, comprising: a spar according to claim 13, wherein the rigid body comprises a hollow internal cavity; one or more airfoil forms mounted to the spar; and an airfoil surface formed from a composite material that surrounds the spar and the airfoil forms.