Variable Gage Composite Structure with Tapered Drop-off Plies
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Solution Overview
Problem
Existing composite structures with variable gages face issues such as large resin pockets and increased risk of delamination and ply kinks due to blunt-end shaped drop-off ply tips arranged in clusters, which reduce laminate strength and increase material handling costs.
Innovation Solution
The use of tapered-shaped drop-off plies arranged in a monotonically-inward or outward pattern, separated by continuous plies, to minimize resin pockets and prevent ply kinks, enhancing interlaminar strength and load-bearing properties while simplifying tooling and reducing material handling costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If blunt-end shaped drop-off ply tips are arranged in clusters to achieve variable gage, then the composite structure can be formed with different thicknesses at different ends, but large resin pockets and increased risk of delamination and ply kinks occur, reducing laminate strength
Solution Approach 1:
The invention changes the geometric parameter of drop-off ply tips from blunt-end shape to tapered shape. This parameter change eliminates the formation of large resin pockets and reduces the risk of delamination and ply kinks, thereby maintaining laminate strength while achieving variable gage composite structures
Solution Approach 2:
The invention introduces asymmetry in the arrangement of drop-off ply tips by using a monotonically-inward pattern where tips are offset from the central portion toward one end. This asymmetric arrangement prevents clustering and distributes resin pockets uniformly, improving interlaminar strength and load-bearing properties
2Shape
If blunt-end shaped drop-off ply tips are arranged in clusters to achieve variable gage, then the composite structure can be formed with different thicknesses, but material handling costs increase due to reduced laminate strength and quality issues
Solution Approach 1:
Changing the tip shape parameter to tapered reduces manufacturing defects and improves quality, thereby reducing material handling costs and improving ease of manufacture while maintaining variable gage capability
Solution Approach 2:
The invention segments the drop-off plies into different subsets (first subset between first outer surface and central portion, second subset between central portion and second outer surface) with different tip arrangements. This segmentation allows optimized handling and reduced quality issues, lowering material handling costs
3Strength
If drop-off plies are arranged in a monotonically-inward pattern with tapered tips, then interlaminar strength and load-bearing properties are enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The monotonically-inward pattern creates an asymmetric arrangement where drop-off ply tips are offset from the central portion. While this improves interlaminar strength, it does increase manufacturing complexity. However, the complexity is manageable through systematic arrangement rules
4Shape
If symmetric arrangement of drop-off plies is used, then structural symmetry is achieved, but resin pockets and delamination risks increase
Solution Approach 1:
The invention deliberately introduces asymmetry in the drop-off ply arrangement through the monotonically-inward pattern, offsetting tips from the central portion. This asymmetric arrangement prevents resin pocket accumulation and reduces delamination risk, improving reliability while maintaining acceptable structural symmetry
Data Source
AI summary
In an example, a composite structure having a variable gage is described. The composite structure includes a first end having a first gage, a second end having a second gage, which is less than the first gage, a plurality of continuous plies, and a plurality of drop-off plies. Each continuous ply extends from the first end to the second end. Each drop-off ply includes a tip having a tapered shape. Each drop-off ply extends from the first end to a respective position of the tip of the drop-off ply between the first end and the second end. The tips of the plurality of drop-off plies are arranged in a monotonically-inward pattern.