Triangular Braided Radius Filler for Composite Structures
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Solution Overview
Problem
Existing radius fillers for composite structures suffer from cracking due to residual stress during manufacturing and sub-optimal pull-off strength under structural loading, which affects the durability and strength of composite structures like aircraft components.
Innovation Solution
A braided radius filler with a plurality of fibers encapsulated in resin, formed into a triangular shape with concave side surfaces and a planar base surface, and a sleeved radius filler with a core covered by a braided sleeve, both designed to minimize cracking and enhance pull-off strength by matching the thermal expansion of adjacent laminates and distributing loads effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing radius fillers are used to fill radius filler regions in composite structures, then the radius filler regions are filled to improve strength and stiffness, but cracking occurs due to residual stress during manufacturing and pull-off strength is sub-optimal under structural loading
Solution Approach 1:
The patent applies parameter changes by modifying the coefficient of thermal expansion (CTE) of the radius filler material to match that of the adjacent composite laminates. This is achieved by formulating the resin system and fiber composition to achieve a CTE match, thereby eliminating residual stresses during cooling from cure temperature and preventing cracking while maintaining pull-off strength
Solution Approach 2:
The patent uses composite materials by creating a radius filler composed of fibers embedded in a resin matrix specifically designed to match the thermal and mechanical properties of the surrounding composite structure. This composite approach allows simultaneous optimization of strength, stiffness, and thermal expansion characteristics
2Reliability
If the coefficient of thermal expansion of the radius filler does not match the adjacent composite laminates, then manufacturing is simplified, but residual stress occurs during cool-down from curing causing cracking
Solution Approach 1:
The patent modifies the CTE parameter of the radius filler through material formulation, adjusting resin composition and fiber content to achieve thermal expansion matching with the composite laminates. This eliminates the harmful residual stresses that cause cracking during cool-down from cure temperature
Solution Approach 2:
The patent directly addresses thermal expansion by designing the radius filler material to have a coefficient of thermal expansion that matches the adjacent composite laminates. This thermal matching prevents differential expansion and contraction during temperature changes, eliminating the root cause of manufacturing-induced cracking
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 braided and sleeved radius fillers significantly reduce crack initiation and growth, improving the pull-off load capability and durability of composite structures by matching thermal expansion and distributing loads, thereby enhancing the structural integrity of components like aircraft stabilizers.
Implementation Method 1
both designed to minimize cracking and enhance pull-off strength by matching the thermal expansion of adjacent laminates
Implementation Method 2
distributing loads effectively, improving the pull-off load capability and durability of composite structures
Data Source
AI summary
A radius filler includes a plurality of fibers encapsulated in resin and braided into a braided radius filler. The braided radius filler has a substantially triangular shape with concave radius filler side surfaces and a substantially planar radius filler base surface.