Composite Bulkhead Skin Integration for Weight Reduction
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Solution Overview
Problem
Current composite aircraft fuselage construction methods require excessive fasteners and complexity, leading to weight and cost penalties, particularly in joining bulkheads to the skin, which can be mitigated by integrating the outer cap structural element into the skin to enhance strength and reduce weight.
Innovation Solution
The outer cap of the fuselage bulkhead is integrated into the skin by layering it to surround the cap, allowing for co-curing or secondary bonding, reducing the need for multiple fasteners and eliminating cutouts for stringers, thereby creating a continuous hoop for increased strength and reduced complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulkheads are joined to the skin with an intermediary clip and two rows of fasteners, then the joining effectiveness is improved, but the quantity of fasteners, weight, complexity, and cost increase significantly
Solution Approach 1:
The patent merges the intermediary clip with the bulkhead structure itself, creating an integrated design where the bulkhead extends to form the cap that directly engages with the skin. This eliminates the separate clip component and reduces the fastener system from two rows to one row, directly addressing the contradiction by combining functions into a unified structure.
Solution Approach 2:
The patent extracts and eliminates the intermediary clip from the assembly, removing the unnecessary component that caused the need for two rows of fasteners. By taking out this intermediate element, the design achieves direct connection between the bulkhead and skin, reducing complexity while maintaining joining effectiveness.
2Device complexity
If the outer cap of the bulkhead is integrated into the skin by layering, then the weight and complexity are reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-forming the outer cap as an integral part of the bulkhead before assembly. The cap is shaped and positioned in advance during bulkhead manufacturing, so that when the bulkhead is installed, the cap is already ready to engage with the skin layers, simplifying the overall assembly process despite the integrated design.
Solution Approach 2:
The patent implements nesting by placing the outer cap within the skin structure through layering. The cap is nested between skin layers or integrated into the skin laminate, creating a compact integrated structure that reduces overall complexity while requiring coordinated manufacturing steps.
3Ease of manufacture
If cutouts are made in bulkheads for stringers, then the stringer installation is facilitated, but the bulkhead strength and continuity are reduced
Solution Approach 1:
The patent applies inversion by reversing the traditional approach: instead of cutting openings in the bulkhead for stringers, the stringers are routed around the bulkhead or the bulkhead is designed to accommodate stringers without discontinuities. This maintains bulkhead continuity and strength while still facilitating stringer installation through alternative routing paths.
Data Source
AI summary
Aircraft fuselage structures have fuselage bulkheads in which the bulkhead outer caps are integrated with the skin, thereby reducing fastener count and weight. These outer caps and skin are preferably co-cured to form a strong structure. The outer caps can be advantageously constructed as continuous hoops of pultruded elements. The outer cap need not be interrupted by contours or cutouts for stringers, saving weight and reducing complexity. It is contemplated that by integrating the bulkhead outer caps into the skin, a bulkhead can still maintain equivalent stiffness and strength, while saving a significant number of rivets as compared to a comparable design without the outer cap.