Composite joint protection
The present invention relates to a joint between a laminar composite cover ( 12 ) and a second cover ( 15 ) (which may or may not be also formed from a composite material). The invention also relates to a method of manufacturing such a joint and a method of manufacturing a composite cover suitable for use in such a joint. The laminar composite cover ( 12 ) comprises a stack of layers, substantially all of the layers being shaped to form a joggle, each joggle comprising a first portion, a second portion where the layer extends substantially parallel with the first portion, and a ramp ( 33 ) between the first and second portions where the layer extends at an angle to the first and second portions, the number of layers being substantially the same on both sides of the ramp. The second cover ( 15 ) partially overlaps with the composite cover, and a clamp or fastener ( 31 ) holds the covers together where they overlap. The covers have external sides which are substantially aligned with each other so as to form a smooth aerodynamic surface.
1. A method of manufacturing an aircraft joint between a laminar composite cover and a second cover, the method comprising:
providing said laminar composite cover comprising a stack of layers, substantially all of the layers being shaped to form a joggle, each joggle comprising
a first portion having a plurality of said layers,
a second portion having a plurality of said layers where the second portion layers extend substantially parallel with the first portion layers, and
a ramp having a plurality of layers located between the first and second portions where the plurality of layers extend at an angle to the first and second portions, the number of layers in said first and second portions are substantially the same on both sides of the ramp;
partially overlapping said second cover with said composite cover;
holding the covers together where they overlap with a clamp or fastener;
substantially aligning external sides of the covers with each other so as to form a smooth aerodynamic surface;
pre-forming a protector with a tapered shape; and
attaching said pre-formed protector to one of the covers before the covers are overlapped, wherein said protector and said external sides of said covers form a substantially continuous external aerodynamic surface.
2. The method of claim 1 wherein the protector is cocured with the composite cover.
3. The method of claim 1 further comprising preforming the protector by pulling or extruding material through a die with a desired crosssectional shape.
4. A method of manufacturing a composite cover, the method comprising:
pre-forming a protector with a tapered shape, wherein the protector tapers gradually from a thick end to a thin edge;
mounting the protector on a mold tool such that the thick end of the protector is positioned adjacent to a step on a mold surface of the mold tool, the mold surface having a first portion adjoining a top of the step and a second portion adjoining a bottom of the step;
laying a stack of layers of composite material on the protector on the mold tool whereby at least one of the layers forms a ramp, the composite cover having an outer mold line and the outer mold line engaging the first portion of the mold surface, the protector and the second portion of the mold surface; and
curing the stack of layers of composite material.
5. The method of claim 4 , wherein the protector is co-cured with the stack of layers of composite material.
6. The method of claim 4 further comprising at least partially curing the protector before it is mounted on the mold tool.
7. The method of claim 4 wherein the protector is preformed by pulling or extruding material through a die with a tapered cross-sectional shape.
8. The method of claim 4 wherein substantially all of the layers are shaped to form a joggle, each joggle comprising:
a first portion,
a second portion where the layer extends substantially parallel with the first portion,
the ramp is between the first and second portions where the ramp extends at an angle to the first and second portions, and
the number of layers being substantially the same on both sides of the ramp.
9. A method to manufacture a cover formed of layers of a composite material, the method comprising:
pre-forming a protector strip having a tapered cross-sectional shape, wherein one edge of the protector strip is thick and an opposite edge of the protector is thin;
positioning the protector strip on a mold surface such that the thick edge of the protector is adjacent a step in the surface and the thin edge is adjacent a flat region of the mold surface, the mold surface having a first portion adjoining a top of the step and a second portion adjoining a bottom of the step;
laying the layers of composite material over the positioned protector strip and over the mold surface to form a stack of layers, wherein the stack of layers includes a ramp aligned with the protector strip, the composite cover having an outer mold line and the outer mold line engaging the first portion of the mold surface, the protector and the second portion of the mold surface, and
curing the stack of layers of composite material.