Composite Sandwich Edge Joint for Higher Line Loads
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Solution Overview
Problem
Existing composite fluted core sandwich shell wall assemblies for space launch vehicles face challenges in carrying higher line loads due to lighter load shell edge joints, which require larger openings for tooling extraction, limiting the spacing of fasteners and forcing load into face sheets, necessitating additional doubler structures not originally designed for such loads.
Innovation Solution
A composite wall assembly edge joint design featuring a first composite buildup pad with a tapered section and an integrally formed composite flute core member, allowing for closer fastener spacing and enhanced load distribution without significant weight increase, by positioning tapered portions of the flute core member between buildup pads and face sheets, and using a bridge composite structure for securement with barrel nuts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lighter load shell edge joints with larger openings are used, then tooling extraction is enabled, but fastener spacing is limited and load capacity is reduced
Solution Approach 1:
The edge joint is divided into multiple reinforcement pads (first and second buildup pads) with tapered sections, allowing the structure to be segmented in a way that provides both openings for tooling extraction and sufficient load-bearing areas for fastener spacing
Solution Approach 2:
The reinforcement pads extend in multiple directions (first direction away from first end, second direction away from second end) to create a three-dimensional load distribution network that accommodates both tooling access and high load capacity requirements
2Ease of manufacture
If larger openings are provided between spaced shell edge reinforcements, then tooling can be extracted, but fasteners cannot be closely spaced
Solution Approach 1:
The edge joint construction is segmented into multiple reinforcement pads that create distinct zones: larger openings for tooling extraction and smaller zones for fastener installation, allowing both requirements to be satisfied simultaneously
3Strength
If load is forced into face sheets at flute ends, then joint connection is achieved, but additional doubler structures are needed
Solution Approach 1:
The doubler function is extracted and integrated into the tapered sections of the buildup pads themselves, which provide the necessary load-bearing capacity and geometric transition without requiring separate doubler components
Solution Approach 2:
The buildup pads are merged with the flute core member through integral formation and tapered section bonding, combining the reinforcement and load-bearing functions into a unified structure that eliminates the need for additional doublers
4Strength
If more closely spaced fasteners are used, then load capacity increases, but weight increases
Solution Approach 1:
Composite buildup pads with tapered sections are used to create a lightweight yet high-strength reinforcement structure that enables closely spaced fasteners without proportionally increasing weight, as the composite material provides high strength-to-weight ratio
Data Source
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AI summary
A composite wall assembly edge joint, includes a first composite buildup pad secured to a first composite face sheet with the first composite buildup pad having a first tapered section with a first inclined surface which extends in a first direction and having a second section which extends from the first tapered section with a second surface which extends in a second direction, different from the first direction, toward a first end of the first composite face sheet. The assembly further includes a composite flute core member, having a tapered first portion secured to the first tapered section; a second portion secured to the first composite face sheet; and a third portion which extends in the second direction, away from the tapered first portion, toward the first end of the first composite face sheet secured to the second section.