Method Fabricating Load-Bearing Composites Free From Microbuckling Deformation Up to a Predetermined Load.
Patent, Filed 3 Jul 91, patented 13 Oct 92,
DEPARTMENT OF THE NAVY WASHINGTON DC
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A continuous filament is selected from among a group of appropriate types of filaments, and selection of the filament length and the filament thickness is made as well. A matrix material is selected from a group of appropriate types of matrix materials. Filaments of the selected type, length and thickness are undirectionally imbedded in the selected matrix to provide a uniaxial continuously reinforced composite. The Youngs modulus, Ec, and the shear modulus Gc, are calculated for the composite. Mathematical formulas are provided for calculation of upper and lower bounds of transverse stiffness, B, A mathematical formula is provided for calculation of critical comprehensive stress, Pc. Transverse stiffness, B, is involved as one of the factors in this formula. Either one or the other of the upper bound of B or the lower bound of B are alternatively applied in calculating Pc, depending upon a consideration related to the shape of a cross section of the structural member into which the composite is to be formed. If the shape of the outline of such cross section includes at least one angular break, then the lower bound of B is applied in calculating Pc. If the shape of the outline of such cross section is curvilinear in its entirety, then the upper bound of B is applied in calculating Pc. A structural member subjected to load values below P, will be free from load-induced microbuckling with a high degree of certainty.
- Laminates and Composite Materials