Tapered Fuselage Splice Fitting Eliminates Shims
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Solution Overview
Problem
Current fuselage section joining methods using carbon fiber reinforced polymer (CFRP) require shims and fillers to align splice fittings, increasing assembly time and cost due to tolerance issues between mating components.
Innovation Solution
A fuselage structure splice system with a strap and stringer configuration, featuring a fitting with a stringer base portion and strap base portion connected by an intermediate base portion, allowing for angled orientations and uniform thickness, which facilitates a shimless joint by accommodating differences in thickness and orientation between the strap and stringer flanges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional splice fittings are used with flat configurations, then the structural joining function is achieved, but numerous shims and fillers are required to align the fittings, increasing assembly time and cost
Solution Approach 1:
The patent applies parameter changes by transitioning from flat splice fittings to tapered splice fittings. The tapered configuration changes the geometric parameter of the fitting, allowing it to self-align during assembly by tapering toward the centerline of the fuselage section, thereby eliminating the need for numerous shims and fillers while maintaining structural joining function
Solution Approach 2:
The tapered splice fitting design enables self-alignment during assembly. The fitting automatically positions itself relative to the stringer and strap components through its tapered geometry, eliminating the need for external alignment tools or additional shim components, thus reducing assembly complexity and time
2Manufacturing precision
If shims are used to compensate for tolerances between mating components, then alignment accuracy is improved, but assembly cost and time increase
Solution Approach 1:
The tapered geometry of the splice fitting is designed in advance to compensate for tolerances between mating components. The fitting configuration is pre-engineered with the appropriate taper angle and dimensions so that during assembly, the fitting naturally accommodates dimensional variations without requiring additional shim components, thereby maintaining alignment accuracy while reducing assembly time
3Strength
If flat splice fittings are used, then the structural strength is maintained, but the fuselage surface requires additional shimming to achieve smooth aerodynamic contours
Solution Approach 1:
The patent changes the geometric parameter of the splice fitting from flat to tapered configuration. This parameter change allows the fitting to maintain structural strength while enabling the fuselage surface to achieve smooth aerodynamic contours without additional shimming, as the tapered fitting naturally conforms to the curved surface geometry
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A fuselage structure splice (106) may include a panel (111) having an edge (113) and a strap (120) connected to the first panel along the panel edge (113). A strap surface (123) not in contact with the panel tapers toward the panel with distance from the panel edge. A stringer (114) is mounted on the panel and extends away from the edge of the panel and has a flange (126) mounted to the panel. A fitting (100) has a stringer base portion (132) and a strap base portion (131). The stringer base portion is connected to the stringer flange and extends along a first line (146) extending in a plane (P1) normal to the panel edge. The strap base portion of the fitting is mounted on the strap surface and extends along a second line (147) in the plane (P1). The second line is transverse to the first line and the strap base portion of the fitting has a constant thickness along the second line.