High strength composite structure
First Claim
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1. A composite structure comprising:
- a skin sheet;
a uniform repeating triangular pattern of first upstanding ribs integral with said skin, across at least a portion of said skin;
a circular node at each corner of each triangle surrounded by a circular second rib;
each of said first and second ribs having a narrow first flange along the upper edge, lying substantially parallel to said skin and a narrow second flange formed by a thickened portion of said skin adjacent to said first and second ribs, whereby said first and second ribs have a substantially I-beam cross-section;
a groove in the outer surface of each flange on said first ribs filled with a composite material strip comprising high-strength fibers embedded in a supporting matrix;
said fibers being oriented substantially parallel to each other and to the supporting first rib, at least some of said fibers extending inwardly of said second rib at each node; and
said fiber strips being tapered at each end to a lesser cross-sectioned fiber density.
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Abstract
An isogrid structure having inset strips of composite materials at the top and bottom of the grid webs. A preferably flanged isogrid basically consists of I-beam members arranged in an integral repeating pattern of substantially equilateral triangles. One flange may be integral with a skin sheet covering the structure. At least some of these flanges are provided with grooves running parallel to the beam webs, filled with advanced composite materials comprising high-strength fibers in a supporting matrix. Preferably, the fibers run parallel to the beam webs. Preferred arrangements of the fibers are described.
84 Citations
10 Claims
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1. A composite structure comprising:
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a skin sheet; a uniform repeating triangular pattern of first upstanding ribs integral with said skin, across at least a portion of said skin; a circular node at each corner of each triangle surrounded by a circular second rib; each of said first and second ribs having a narrow first flange along the upper edge, lying substantially parallel to said skin and a narrow second flange formed by a thickened portion of said skin adjacent to said first and second ribs, whereby said first and second ribs have a substantially I-beam cross-section; a groove in the outer surface of each flange on said first ribs filled with a composite material strip comprising high-strength fibers embedded in a supporting matrix; said fibers being oriented substantially parallel to each other and to the supporting first rib, at least some of said fibers extending inwardly of said second rib at each node; and said fiber strips being tapered at each end to a lesser cross-sectioned fiber density. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In an isogrid structure comprising:
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a uniform repeating triangular pattern of first upstanding ribs, each rib having an upper and a lower edge; a circular node at each corner of each triangle;
each node being surrounded by a circular second rib;narrow parallel upper and lower flanges along the upper and lower edges of each of said first and second ribs, respectively; a skin sheet integral with said lower flanges; the improvement comprising; wide, shallow grooves in the upper surface of each upper flange on each first rib, said grooves filled with a composite material strip comprising fibers having a composition selected from the group consisting of boron, graphite and mixtures thereof, embedded in a supporting matrix; said fibers lying substantially parallel to each other and to said first ribs; at least some of said fibers extending inwardly at said nodes beyond said second ribs; said fiber strip tapering at each end to a lesser cross-sectioned fiber density. - View Dependent Claims (8, 9, 10)
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Specification