Method of producing a composite sine wave beam

A process for producing a composite structural sine wave beam which comprises the steps of

• providing a two part longitudinally extending mandrel formed of two like sections, said sections each having a front side of matching sine wave configuration, said sections capable of being nested together along said front sides, said sections each having a planar back side and top and bottom planar surfaces,
• placing graphite-epoxy tape plies in contact with the front sine wave configured side of each of said mandrel sections, so that said tape plies have a sine wave configuration,
• assembling said mandrel sections together in secured relation, with the planar back sides thereof in contact,
• passing said assembled mandrel sections through a braiding apparatus, and surrounding the entire circumference of said assembled mandrel sections including the top and bottom planar surfaces of said mandrel sections and the sine wave configured sides thereof containing said tape plies, with a braiding material in the form of a pre-preg tow of resin coated graphite fibers, said mandrel sections each having slightly rounded edges at the intersection of the sine wave configured sides thereof with the top and bottom surfaces thereof, to prevent cutting of said braiding material,
• heat setting the assembly of tape plies on the front sides of said mandrel sections and the braided material thereover, to compact such assembly,
• cutting the braided material along a prescribed center line on the top and bottom surfaces of the mandrel sections along the upper and lower edges of the back sides of said sections,
• separating and repositioning the mandrel sections, with the front sine wave configured sides containing said sine wave configured tape plies and the braided material thereon, nested together in face-to-face contact, to form the sine wave web of said beam,
• inserting a graphite-epoxy tape filler in the void formed along the adjacent sinuous rounded edges of said mandrel sections on the top and bottom surfaces thereof,
• placing a cap sheet formed of plies of graphite-epoxy resin over the braided material and over the sinuous tape filler on the top and bottom surfaces of said repositioned mandrel sections, to form the flanges of said beam, and
• curing the resulting assembly under heat and pressure to form a composite structural sine wave beam.

A process for producing a composite structural beam which comprises the steps of

• providing a longitudinally extending mandrel having four sides including a pair of opposite sides of like predetermined matching configuration and a pair of opposite flat sides,
• braiding the entire circumference of said mandrel with a tow material,
• cutting the braided material on the mandrel along a predetermined longitudinal line on each side of the mandrel, and forming four like quadrants of braided material, each having an L-shaped cross-section, one leg of said L-shaped quadrants extending longitudinally and having said predetermined configuration, the other leg of such L-shaped quadrants extending longitudinally in flat form,
• removing said quadrants from said mandrel,
• providing a tool formed of two like half portions, said half portions each having a side of the same predetermined configuration, and capable of being nested together along said predetermined configured sides, and including a first groove adjacent opposite edges of the configured side of each tool half portion and extending longitudinally in a predetermined configuration corresponding to the predetermined configuration of said one leg of said L-shaped quadrants, and a second flat groove communicating with said first groove and disposed at an angle thereto, said first and second grooves together forming a pair of L-shaped grooves extending along opposite longitudinal edges of said tool half portions,
• placing an L-shaped quadrant of braided material in each of said L-shaped grooves along opposite edges of each of said tool half portions, with said one configured leg of the L-shaped quadrants of braided material in contact with the first configured groove of said L-shaped groove of said tool half portions, and said other leg of the L-shaped quadrants in contact with the second groove of said L-shaped groove,
• placing a sheet of flexible composite material formed of fiber reinforced heat curable resin material in contact with the configured side of each tool half portion and overlying the configured leg of the L-shaped braided quadrants extending along opposite edges of each tool half portion, said flexible composite sheet thereby assuming the configuration of the configured side of said tool half portion and of the configured legs of said L-shaped quadrants,
• assembling the tool half portions, with the configured sides thereof containing said composite sheets and the braided quadrants thereon, nested together in face-to-face contact, and with the opposite edge portions of said composite sheets sandwiched between the adjacent configured legs of the L-shaped braided quadrants,
• placing a cap sheet of fiber reinforced partially cured resin over the other flat legs of said L-shaped braided quadrants disposed in the flat grooves extending along the opposite longitudinal edges of said tool half portions, and
• curing the composite sheets on the configured side of the tool half portions and the cap sheets under heat and pressure to form a composite structural beam, said braided quadrants being bonded to said composite sheets and to said cap sheets, said cured composite sheets and the bonded configured legs of said L-shaped quadrants adjacent opposite edges of said sheets forming the web of said composite beam, and said cured cap sheets and the bonded flat legs of said braided quadrants forming the flanges of said beam, said web and flanges connected at their junctures by said braided quadrants.