Variable-Radius Laminated Composite Radius Filler for I-Beam Cracking
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Solution Overview
Problem
Existing radius fillers for composite structures suffer from cracking during manufacturing, low pull-off strength, and hinder non-destructive inspection due to residual stress and geometry issues, particularly in I-beam shapes.
Innovation Solution
A variable-radius laminated composite radius filler with a base, keyway, and tip portion, formed from stacked composite plies with varying widths, is developed, allowing for a variable cross-sectional shape that minimizes cracking and improves inspectability by maintaining a constant stiffener inner radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If existing radius fillers are used to fill the notch regions in composite I-beams, then the structural completeness is improved, but cracking occurs due to residual stress during manufacturing
Solution Approach 1:
The radius filler is divided into multiple discrete plies (e.g., 3-5 plies) stacked together to form the filler structure. Each ply can independently accommodate stress variations, preventing crack propagation through the entire filler thickness. This segmentation approach directly addresses the cracking issue while maintaining structural completeness.
Solution Approach 2:
The radius filler is constructed using composite material plies (e.g., carbon fiber reinforced polymer) that match the surrounding I-beam structure. These composite plies provide both structural integrity and compatibility with the host structure, ensuring stress distribution that minimizes residual stress-induced cracking while completing the structural form.
2Stability of the object's composition
If existing radius fillers are used to complete the I-beam structure, then the structural integrity is improved, but pull-off strength at the bond between I-beam and skin panel remains low
Solution Approach 1:
The radius filler plies are oriented and configured to concentrate bonding strength at the critical interface regions where the I-beam meets the skin panel. The local ply arrangement creates enhanced adhesion zones that specifically target the bond line, improving pull-off strength without compromising overall structural integrity.
3Ease of manufacture
If unidirectional fiber radius fillers are used, then the manufacturing process is simplified, but non-destructive inspection of the inner radii is prevented due to adverse effects on acoustic transmission
Solution Approach 1:
The radius filler uses composite plies with fiber orientations specifically designed to be acoustically transparent to ultrasonic inspection waves. By selecting appropriate fiber directions (e.g., alternating +/- 45 degree orientations) and material properties, the filler maintains structural function while allowing acoustic signals to pass through for effective non-destructive inspection of the inner radii.
4Strength
If localized increases in composite thickness are added to improve stiffness characteristics, then the stiffness-to-weight ratio is improved, but variations in the contour of inner radii complicate acoustic inspection
Solution Approach 1:
The radius filler incorporates localized thickness variations that precisely match the varying contour of the inner radii created by localized stiffener thickness changes. This local adaptation ensures constant bond line thickness and uniform acoustic path length, simplifying inspection despite the overall complexity of the stiffened structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces cracking and enhances pull-off strength while enabling effective non-destructive inspection of composite structures, reducing tooling costs and manufacturing complexity.
Implementation Method 1
a variable-radius laminated composite radius filler may include a base portion, a keyway portion, and a tip portion. The base portion may be formed of a plurality of variable width composite plies defining a variable cross-sectional shape of the base portion. The keyway portion may be stacked on the base portion and may be formed of a plurality of substantially constant width composite plies defining a substantially constant cross-sectional shape of the keyway portion.
Data Source
AI summary
A variable-radius laminated composite radius filler may include a base portion, a keyway portion, and a tip portion. The base portion may be formed of a plurality of variable width composite plies defining a variable cross-sectional shape of the base portion. The keyway portion may be stacked on the base portion and may be formed of a plurality of substantially constant width composite plies defining a substantially constant cross-sectional shape of the keyway portion. The tip portion may be stacked on the keyway portion and may be formed of composite plies.