Kinked Composite Structure With Cut Ply Load Path
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Solution Overview
Problem
Forming composite structures with kinks requires cutting and darting, which can degrade strength properties and lead to wrinkling of fibers.
Innovation Solution
A composite structure with a kink is formed using a stack of composite plies, where at least one ply is cut with an array of cuts, including a first and second row of cuts separated by a gap to provide a load path, and the cuts are arranged to minimize fiber wrinkling and maintain structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If cutting and darting is used to form kinks in composite structures, then the structure can be formed with angle changes, but the strength properties are degraded and fiber wrinkling occurs
Solution Approach 1:
The invention divides the continuous fiber ply into multiple segments by making an array of parallel cuts. This segmentation allows the ply to accommodate the kink geometry without requiring traditional darting, thereby maintaining fiber continuity and strength while enabling the desired angular change in structure shape.
Solution Approach 2:
The cuts are strategically positioned only at the kink location rather than throughout the entire structure. This localized modification allows the kink to be formed with proper fiber accommodation only where needed, preserving the continuous load path and strength properties in the non-kinked regions of the composite structure.
2Shape
If traditional cutting and darting is used to form kinks, then angle changes can be achieved, but fiber wrinkling occurs which degrades structural integrity
Solution Approach 1:
By segmenting the ply through parallel cuts at the kink location, the invention eliminates the need for darting that causes fiber wrinkling. The segmented structure allows fibers to follow the kink geometry smoothly without buckling or wrinkling, achieving angle changes while maintaining fiber integrity.
Solution Approach 2:
The invention transitions from traditional 2D darting (cutting patterns on a single plane) to a 3D array of parallel cuts that accommodate the kink in multiple dimensions. This dimensional approach allows fibers to bend smoothly through the kink without wrinkling, achieving the desired angular change while preserving fiber continuity.
3Shape
If an array of cuts is made in a ply to form a kink, then the ply can accommodate the kink geometry, but the load path may be disrupted
Solution Approach 1:
The invention uses a series of parallel cuts rather than a single cut or dart, creating multiple partial severances that collectively accommodate the kink geometry. This partial action approach maintains sufficient fiber continuity between cuts to preserve the load path, while still allowing the ply to bend smoothly through the kink without wrinkling.
Solution Approach 2:
The array of parallel cuts acts as an intermediary structure between the continuous fiber ply and the kink geometry. The cuts provide a transition zone that allows the fibers to follow the angular change while maintaining load transfer capability, effectively mediating between the conflicting requirements of shape change and load path continuity.
Data Source
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AI summary
A composite structure comprising: a stack of composite plies, each composite ply comprising a layer of fibres. The stack is formed with a kink with an inner side and an outer side. At least one of the plies is a cut ply with an array of cuts located at the kink. Each cut severs a group of the fibres of the cut ply; and the array of cuts comprises a first row of cuts and a second row of cuts separated by a gap. The first row of cuts is closer to the inner side of the kink than the second row of cuts. The gap provides a load path across the array.