Aircraft Window Frame Composite Design for Fiber Wrinkling
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Solution Overview
Problem
Aircraft window frames made from continuous fiber reinforced composites face challenges with wrinkling of reinforcing fibers due to tight radii of curvature and require additional parts in window pane retention systems, affecting strength and complexity.
Innovation Solution
A window frame configuration using a ring-shaped base of continuous fiber reinforced thermoplastic composite with a circumferential flange and non-planar skirt portion, featuring overmolded protrusions and an aero filler to reduce curvature and simplify the structure, along with a method of stamp-forming and overmolding to integrate these features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If continuous fiber reinforced composite window frames are formed with tight radii of curvature to follow the window aperture and support the window pane, then the window frame can be made lighter and maintain structural integrity, but the reinforcing fibers wrinkle during manufacture which reduces the strength of the window frame
Solution Approach 1:
The window frame is divided into multiple sections with different radius of curvature values. The first section has a first radius of curvature and the second section has a second radius of curvature that is greater than the first radius of curvature. This segmentation allows the frame to follow the window aperture contour while avoiding tight curves that cause fiber wrinkling, thus maintaining both weight efficiency and structural strength.
2Shape
If continuous fiber reinforced composite window frames are formed with tight radii of curvature, then the window frame can support the window pane at the correct position, but additional parts are required in the window pane retention system
Solution Approach 1:
The window frame integrates multiple functions into a unified structure. The first and second sections with different curvatures collectively perform both the aperture-following function and the window pane support function. This merging eliminates the need for additional separate retention parts, simplifying the overall system while maintaining the required geometric precision for proper window pane positioning.
3Weight of moving object
If the window frame is formed from continuous fiber reinforced composite with complex doubly-curved geometry, then weight is reduced compared to metal alloys, but fiber wrinkling occurs during manufacture affecting strength
Solution Approach 1:
The complex doubly-curved geometry is segmented into two distinct sections, each with controlled radius of curvature values. The first section handles the aperture contour following with a smaller first radius, while the second section provides structural support with a larger second radius. This segmentation simplifies the manufacturing process by avoiding extremely tight curves, thereby preventing fiber wrinkling and improving fiber layout precision while maintaining the weight advantages of composite materials.
Data Source
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AI summary
Aircraft window assemblies and methods. The aircraft window assemblies comprise a window frame (102) configured to support a window pane (126) on an aircraft skin (12) about a window aperture (14) defined in an aircraft skin (12). The window frame (102) includes a base (104) formed of a continuous fiber reinforced thermoplastic composite and at least one overmolded feature molded to the base. The base (104) defines a central aperture (106) and includes circumferential flange portion configured to support the base (104) on the aircraft skin (12) surrounding the window aperture and a skirt portion (110) extending inwardly from the circumferential flange portion (108) and surrounding the central aperture (106). The skirt portion (110) is non-planar with the circumferential flange portion (108) and comprises a support surface for the window pane (126). The methods comprise forming the window frame (102), which comprises stamp-forming the base of the window frame from a continuous fiber reinforced thermoplastic composite sheet and overmolding the at least one overmolded feature to the base.