Filament reinforced structural shapes
AssigneeGeneral Dynamics Corporation
InventorsJimmie W. Cogburn, Billie E. Chitwood, Marvin S. Howeth
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Abstract
Strong, lightweight structural shapes or structures adapted for anistropic load bearing useful as structural beams or stiffeners for other structures, e.g., aircraft and which prevent or have improved resistance to forces tending to peel apart the structures, i.e., incipient peel. The shapes are fabricated from plicated laminates of strips or sheets of resinous, filament reinforced, composite materials having high strength and low weight. Fabrication of the shapes is carried out in such manner that upon curing of the resin the resultant stiffener shapes are capable of distributing loading forces so as to reduce localization of stresses.
Claims14
A structural beam formed from a plurality of plies of composite material each containing high tensile strength filaments in a resin matrix laid up together and cocured around a plurality of reinforcing strips of unidirectionally arranged high modulus filaments to form a unitary beam structure combining high strength and low weight with resistance to internal peel forces and crack propagation comprising:
- a. an upper member extending in the longitudinal direction of the beam;
- b. a lower cap member extending in the longitudinal direction of the beam and spaced from said upper cap member;
- c. said upper and lower cap members each having at least one strip-like stiffener means therein containing a plurality of high modulus of elasticity stiffening filaments generally unidirectionally arranged generally parallel to the length of the beam for providing resistance to bending and compression forces at upper and lower or basal portions of said structure;
- d. substantially planar shear web means containing a plurality of layer of high tensile strength filaments integrally connecting said upper and lower cap members for transmitting loading forces therebetween, the filaments of each of said layers being generally transverse with respect to the filaments of said stiffener means;
- e. said filaments held in a resin matrix material for bonding the filaments in the desired configuration and transmitting of loading forces between filaments;
- f. said web means at least at said lower cap member having generally oppositely directed flange portions extending generally transverse to said web means and integrally connected therewith for distributing the loading forces in said shear web means to the lower cap member along oppositely directed paths and to opposite sides of said web means;
- g. said upper cap member stiffener means extending to substantially the full width of the upper cap member;
- and
- h. said lower cap member stiffener means having a prism-like configuration of generally triangular cross-section and disposed longitudinally of the beam between said oppositely directed flange portions of the web means, upper outer-directed surfaces of said lower cap member stiffener means prism-like configuration being formed to a radius-like concave curvature and bonded to inner-directed surfaces of said web means flange portions along said concavely curved surfaces and the lower surface of said configuration being substantially flat and bonded to lower or basal portions of said lower cap member;
- and
- i. the filaments of said stiffener means having a higher modulus of elasticity (Young's modulus) than the filaments of said web member to provide resistance to bending and compression forces;
- whereby a strong, lightweight beam structure is produced in which shear forces tending to separate said flanges from basal portions of the beam act simultaneously in opposite directions distributed over the full upper-directed area of said concavely curved surfaces, thereby decreasing the tendency for peeling forces to separate said web from said lower cap member when loading forces are acting on said beam.
Dependencies are inferred from the claim text.