Skew-angle radius filler reduces delamination in CFRP stringers
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Solution Overview
Problem
Carbon fiber reinforced plastic (CFRP) stringers in aircraft wing structures are prone to delamination due to excessive shear and moment forces, particularly at the noodle regions where ribs are bolted, despite the use of conventional rectangular radius fillers, which can lead to reduced joint capability and undesirable effects.
Innovation Solution
The implementation of skew-angle radius fillers with a radius contact side and non-parallel sides extending at acute angles, designed to match the web joint radius of the stringer, enhances joint capability by redistributing operational loads and reducing the risk of delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rectangular radius fillers are used at the web joint, then the joint provides some structural reinforcement, but delamination still occurs due to localized high shear loads and moments
Solution Approach 1:
The patent applies asymmetry by transitioning from conventional rectangular radius fillers to skew-angle radius fillers with non-parallel sides. The skew-angle configuration creates an asymmetric geometry that better matches the stress distribution pattern at the web joint, allowing the filler to more effectively resist localized high shear loads and moments that cause delamination.
Solution Approach 2:
The patent applies local quality by designing the radius filler with varying thickness across its geometry. The non-parallel sides create regions of different thickness that correspond to different stress concentrations at the web joint, providing enhanced reinforcement precisely where the highest shear loads and moments occur while maintaining appropriate reinforcement elsewhere.
2Reliability
If additional reinforcement is provided at the web joint to prevent delamination, then joint capability is improved, but aircraft weight increases which is undesirable
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the radius filler - specifically the angles and dimensions of the non-parallel sides. These parameter changes optimize the reinforcement efficiency, allowing the joint to achieve improved delamination resistance with a filler that does not significantly increase overall aircraft weight.
Data Source
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AI summary
Technologies are described herein for enhancing joint capability and reducing the risk of delaminating a stringer using skew-angle radius fillers. A skew-angle radius filler (302A, 302B) for enhancing joint capability includes a top surface (303A, 303B) and a bottom surface (305A, 305B) separated by a thickness. The radius filler also includes a radius contact (304A, 304B) side that has an edge radius (307A, 307B) that is sized to match a radius of a web joint of a stringer. The radius filler also includes a pair of opposing non-parallel sides (306A, 308A, 306B, 308B) that extend from the radius contact side at an acute angle, and a rear side (310A, 310B) that is shorter than the radius contact side.