Abstract: Systems and methods are provided for septa for acoustic cells. One embodiment is a method that includes fabricating a septum of a cell of an acoustic panel, by heating a material into a molten material, depositing the molten material to form a lower chamber of the septum that extends vertically upwards and includes an entry, iteratively depositing layers of the molten material, each layer comprising a filament at the entry that includes overhangs with respect to vertically adjacent layers, and forming openings at locations of the overhangs.

Abstract: Systems and methods are provided for septa for acoustic cells. One embodiment is a method that includes fabricating a septum of a cell of an acoustic panel, by heating a material into a molten material, depositing the molten material to form a lower chamber of the septum that extends vertically upwards and includes an entry, iteratively depositing layers of the molten material, each layer comprising a filament at the entry that includes overhangs with respect to vertically adjacent layers, and forming openings at locations of the overhangs.

Abstract: A forming system includes a femtosecond laser and a control unit that includes one or more processors operatively connected to the femtosecond laser. The femtosecond laser is configured to emit laser pulses onto an inner surface of a face sheet of an acoustic inner barrel. The acoustic inner barrel includes an acoustic core comprising an array of hexagonal cells attached to an outer surface of the face sheet that is opposite the inner surface. The control unit is configured to control the femtosecond laser to laser drill a plurality of perforations in the face sheet via emitting laser pulses at pulse durations between about 100 femtoseconds and about 10,000 femtoseconds and at frequencies over 100,000 Hz.

Abstract: A forming system includes a femtosecond laser and a control unit that includes one or more processors operatively connected to the femtosecond laser. The femtosecond laser is configured to emit laser pulses onto an inner surface of a face sheet of an acoustic inner barrel. The acoustic inner barrel includes an acoustic core comprising an array of hexagonal cells attached to an outer surface of the face sheet that is opposite the inner surface. The control unit is configured to control the femtosecond laser to laser drill a plurality of perforations in the face sheet via emitting laser pulses at pulse durations between about 100 femtoseconds and about 10,000 femtoseconds and at frequencies over 100,000 Hz such that the perforations are formed without burning portions of the face sheet or the acoustic core surrounding the perforations.

Abstract: Systems and methods are provided for septa for acoustic cells. One embodiment is a method that includes fabricating a septum of a cell of an acoustic panel, by heating a material into a molten material, depositing the molten material to form a lower chamber of the septum that extends vertically upwards and includes an entry, iteratively depositing layers of the molten material, each layer comprising a filament at the entry that includes overhangs with respect to vertically adjacent layers, and forming openings at locations of the overhangs.

Abstract: A forming system includes a femtosecond laser and a control unit that includes one or more processors operatively connected to the femtosecond laser. The femtosecond laser is configured to emit laser pulses onto an inner surface of a face sheet of an acoustic inner barrel. The acoustic inner barrel includes an acoustic core comprising an array of hexagonal cells attached to an outer surface of the face sheet that is opposite the inner surface. The control unit is configured to control the femtosecond laser to laser drill a plurality of perforations in the face sheet via emitting laser pulses at pulse durations between about 100 femtoseconds and about 10,000 femtoseconds and at frequencies over 100,000 Hz such that the perforations are formed without burning portions of the face sheet or the acoustic core surrounding the perforations.

Abstract: Systems and methods are provided for septa for acoustic cells. One embodiment is a method that includes fabricating a septum of a cell of an acoustic panel, by heating a material into a molten material, depositing the molten material to form a lower chamber of the septum that extends vertically upwards and includes an entry, iteratively depositing layers of the molten material, each layer comprising a filament at the entry that includes overhangs with respect to vertically adjacent layers, and forming openings at locations of the overhangs.

Abstract: A windshield wiper arm is provided on an outside of an aircraft and positioned to directly engage an air flow while the aircraft is traveling. The wiper arm includes an arm portion coupled to the aircraft and having an arm exterior surface, the arm portion extending along an arm axis and defining an arm length. A bead extends outwardly from the arm exterior surface and defines a bead exterior surface, the bead being sized sufficiently to engage a boundary layer of the air flow. A wiper blade is coupled to the arm portion. The bead prevents separation of the boundary layer from the arm exterior surface, thereby to attenuate shedding of vortices and associated vibrations and noise.

Abstract: A windshield wiper arm is provided on an outside of an aircraft and positioned to directly engage an air flow while the aircraft is traveling. The wiper arm includes an arm portion coupled to the aircraft and having an arm exterior surface, the arm portion extending along an arm axis and defining an arm length. A bead extends outwardly from the arm exterior surface and defines a bead exterior surface, the bead being sized sufficiently to engage a boundary layer of the air flow. A wiper blade is coupled to the arm portion. The bead prevents separation of the boundary layer from the arm exterior surface, thereby to attenuate shedding of vortices and associated vibrations and noise.