Abstract: Structurally tunable cores are described that can be implemented, for example, in aircraft components. An example flex beam for coupling a rotor blade to a rotor hub includes a first composite laminate, a second composite laminate, a third composite laminate, first resilient core members and second resilient core members. The first composite laminate forms a first skin of the flex beam. The second composite laminate is located opposite the first composite laminate and forms a second skin of the flex beam. The third composite laminate is located between the first composite laminate and the second composite laminate. The first resilient core members extend between the first composite laminate and the third composite laminate. The second resilient core members extend between the second composite laminate and the third composite laminate.

Abstract: Structurally tunable cores are described that can be implemented, for example, in aircraft components. An example flex beam for coupling a rotor blade to a rotor hub includes a first composite laminate, a second composite laminate, a third composite laminate, first resilient core members and second resilient core members. The first composite laminate forms a first skin of the flex beam. The second composite laminate is located opposite the first composite laminate and forms a second skin of the flex beam. The third composite laminate is located between the first composite laminate and the second composite laminate. The first resilient core members extend between the first composite laminate and the third composite laminate. The second resilient core members extend between the second composite laminate and the third composite laminate.

Abstract: Typical composite panels are brittle and unable to support transverse pressure loads that might be imposed on the panels. For example, the use of typical panels around fuel tanks of a vehicle are unable to support transverse pressure loads that might be imposed on the fuel tanks during a crash of the vehicle or a ballistic impact to the fuel tanks. In the embodiments described herein, panels include face sheets that are bonded to a foam core. The foam core includes a corrugated core sheet that is formed from a highly ductile material, such as Polyethylene or Aluminum. When a transverse pressure load is imposed on the panel, core crush of the foam occurs as the core sheet elongates from its original corrugated shape to a curve shape during deformation. This allows the panel to dissipate the energy of the transverse pressure load applied to the panel.

Abstract: Typical composite panels are brittle and unable to support transverse pressure loads that might be imposed on the panels. For example, the use of typical panels around fuel tanks of a vehicle are unable to support transverse pressure loads that might be imposed on the fuel tanks during a crash of the vehicle or a ballistic impact to the fuel tanks. In the embodiments described herein, panels include face sheets that are bonded to a foam core. The foam core includes a corrugated core sheet that is formed from a highly ductile material, such as Polyethylene or Aluminum. When a transverse pressure load is imposed on the panel, core crush of the foam occurs as the core sheet elongates from its original corrugated shape to a curve shape during deformation. This allows the panel to dissipate the energy of the transverse pressure load applied to the panel.

Abstract: A method and apparatus are presented. The apparatus comprises a first unitary structure, a second unitary structure, and a number of joints between the first unitary structure and the second unitary structure. The first unitary structure has a plurality of T-shaped cross-sections. The second unitary structure has a plurality of T-shaped cross-sections.

Abstract: A composite stiffener is provided with an integral conductive element extending longitudinally through an entire length of the composite stiffener to form a portion of an electrical ground/return system in a composite structure. The integral conductive element provides both structural strength and conductivity, and may be formed from graphite nanotube filaments, carbon nanofibers or nanoparticles, or a metallic filler material. The integral conductive element is disposed in a terminal portion of the composite stiffener and may include a terminal tab for connecting to the ground/return system.

Abstract: A method and apparatus for manufacturing a sandwich structure. A cavity is formed in a core of the sandwich structure. A structural insert is placed into the cavity. The structural insert comprises a first number of parts configured to receive a load and a second number of parts assembled with the first number of parts to form the structural insert.

Abstract: A method and apparatus are presented. The apparatus comprises a first unitary structure, a second unitary structure, and a number of joints between the first unitary structure and the second unitary structure. The first unitary structure has a plurality of T-shaped cross-sections. The second unitary structure has a plurality of T-shaped cross-sections.

Abstract: A composite stiffener is provided with an integral conductive element extending longitudinally through an entire length of the composite stiffener to form a portion of an electrical ground/return system in a composite structure. The integral conductive element provides both structural strength and conductivity, and may be formed from graphite nanotube filaments, carbon nanofibers or nanoparticles, or a metallic filler material. The integral conductive element is disposed in a terminal portion of the composite stiffener and may include a terminal tab for connecting to the ground/return system.

Abstract: Methods and systems for balancing helicopter rotor blades are disclosed. In some examples, density data of a rotor blade may be acquired by scanning the rotor blade. In some examples, surface contour data of a rotor blade may be acquired by scanning the rotor blade. In some examples, simulations may be performed to predict flight data associated with a modeled rotor blade. In some examples, a database may be referenced to predict a desired weight balance and/or a desired aerodynamic balance of a rotor blade.

Abstract: A method and apparatus for manufacturing a sandwich structure. A cavity is formed in a core of the sandwich structure. A structural insert is placed into the cavity. The structural insert comprises a first number of parts configured to receive a load and a second number of parts assembled with the first number of parts to form the structural insert.

Abstract: A hub joint for supporting bearings adapted to rotatably receive a shaft. The joint includes an upper annular portion having a radially inner boundary and an upper bearing mount attached to the inner boundary of the upper annular portion. The upper bearing mount has a radially inner surface forming a conical upper bearing seat. The joint further comprises a lower bearing mount attached to and positioned below the upper bearing mount. The lower bearing mount has a radially inner surface forming a conical lower bearing seat. The joint also comprises a lower annular portion having a radially inner boundary attached to the lower bearing mount.

Abstract: A hub joint for supporting bearings adapted to rotatably receive a shaft. The joint includes an upper annular portion having a radially inner boundary and an upper bearing mount attached to the inner boundary of the upper annular portion. The upper bearing mount has a radially inner surface forming a conical upper bearing seat. The joint further comprises a lower bearing mount attached to and positioned below the upper bearing mount. The lower bearing mount has a radially inner surface forming a conical lower bearing seat. The joint also comprises a lower annular portion having a radially inner boundary attached to the lower bearing mount.

Abstract: A method of fabricating a damage tolerant shaft is provided in which a plurality of lobes are initially formed and are then positioned relative to one another to define an annular body and a plurality of ribs extending within the annular body. The plurality of lobes are formed of a plurality of reinforcing fibers extending at least partially about a respective lobe. Once the lobes have been positioned relative to one another, interstices between portions of adjacent lobes may be filled. Additionally, the plurality of lobes may be surrounded by an outer layer, also formed of reinforcing fibers extending at least partially about the plurality of lobes. The plurality of lobes may be impregnated with resin and cured, either prior to being positioned relative to one another or thereafter.

Abstract: The damage tolerant shaft and associated method of fabricating a damage tolerant shaft provide a drive shaft that is tolerant of accidental and projectile damage to a portion of the drive shaft. The damage tolerant drive shaft is designed with internal ribs or lobes, such that a closed portion of the drive shaft will likely remain after the drive shaft is partially damaged. Thus, the damage tolerant drive shaft is able to continue proper operation after being partially damaged because the closed portion of the shaft creates a closed path around which the internal shear stresses that correspond to the required torque loads flow. In addition, the damage tolerant shaft and associated method provide damage tolerance without increasing the radius, wall thickness and/or weight of the drive shaft.

Abstract: A hollow core composite assembly 10 is provided, including a hollow core base 12 having an open core surface 14, a polyetherketoneketone film 22 applied to the hollow core base 12, and an adhesive layer 24 positioned between the polyetherketoneketone film 22 and the open core surface 14. The resultant hollow core composite assembly 10 can be cured to provide a structure suitable for use within a liquid molding process.

Abstract: A hollow core composite assembly 10 is provided, including a hollow core base 12 having an open core surface 14, a polyetherketoneketone film 22 applied to the hollow core base 12, and an adhesive layer 24 positioned between the polyetherketoneketone film 22 and the open core surface 14. The resultant hollow core composite assembly 10 can be cured to provide a structure suitable for use within a liquid molding process.

Abstract: The damage tolerant shaft and associated method of fabricating a damage tolerant shaft provide a drive shaft that is tolerant of accidental and projectile damage to a portion of the drive shaft. The damage tolerant drive shaft is designed with internal ribs or lobes, such that a closed portion of the drive shaft will likely remain after the drive shaft is partially damaged. Thus, the damage tolerant drive shaft is able to continue proper operation after being partially damaged because the closed portion of the shaft creates a closed path around which the internal shear stresses that correspond to the required torque loads flow. In addition, the damage tolerant shaft and associated method provide damage tolerance without increasing the radius, wall thickness and/or weight of the drive shaft.

Abstract: The damage tolerant shaft and associated method of fabricating a damage tolerant shaft provide a drive shaft that is tolerant of accidental and projectile damage to a portion of the drive shaft. The damage tolerant drive shaft is designed with internal ribs or lobes, such that a closed portion of the drive shaft will likely remain after the drive shaft is partially damaged. Thus, the damage tolerant drive shaft is able to continue proper operation after being partially damaged because the closed portion of the shaft creates a closed path around which the internal shear stresses that correspond to the required torque loads flow. In addition, the damage tolerant shaft and associated method provide damage tolerance without increasing the radius, wall thickness and/or weight of the drive shaft.

Abstract: A heat sealable, adhesive-free seam and closure fabrics and clothing comprising the combination of a fabric scrim and a heat sealable water and vapor resistant coextruded laminations which provides a barrier against liquid substances and vapors. The coextrusion laminations are in abutment or overlap and comprise a film layer with an outer and inner layer of low density polyethylene and an intermediate layer of a copolymer of ethylene and vinyl alcohol. The laminations are fusion bonded to a portion of the scrim in a manner whereby the polyethylene flows from said lamination, encapsulates the ends of the intermediate layer of the laminate and forms weld points with the said scrim to prevent penetration by liquid substances and vapors.