Curved composite frames and method of making the same
A curved composite aircraft frame comprises a multi-ply composite laminate having a generally Z-shaped cross section. At least certain of the laminate plies include unidirectional reinforcing fibers that are substantially tangent at substantially all points along the curvature of the frame.
1. A method of fabricating a curved one-piece frame for an aircraft having an integrated shear tie, comprising:
defining a curvature of the curved one-piece frame using a polar coordinate reference system;
assembling a composite layup, including:
laying up multiple plies of composite material including resin reinforced unidirectional fibers, each of the multiple plies having an angular fiber orientation, and
using the polar coordinate reference system to orient each of the multiple plies relative to the curvature as the multiple plies are being laid up, laying down composite fibers on a tool such that the composite fibers are substantially tangent to the curvature at substantially all points along the curvature, and wherein orienting each of the multiple plies relative to the curvature using the polar coordinate reference system further includes varying a quantity or composition of the multiple plies within the curved one-piece frame, along an arc length or a width of the curved one-piece frame;
placing the composite layup on a tool;
drawing the composite layup down onto the tool; and
after drawing the composite layup down onto the tool, curing the composite layup.
2. The method of claim 1 , further comprising: laying down composite fibers on the tool using a computer controlled automatic fiber placement machine.
3. The method of claim 1 , further comprising: the tool comprising a first surface, a second surface, and a third surface.
4. The method of claim 1 , further comprising bending edges of the layup over the tool.
5. The method of claim 1 , further comprising: vacuum bag forming the composite layup on the tool.
6. The method of claim 1 , further comprising: drawing the composite layup down on a first surface of the tool to form an inner chord, drawing the composite layup down on a second surface of the tool to form an outer chord, and drawing the composite layup down on a third surface of the tool to form a web connecting the inner chord and the outer chord.