Variable-Stiffness Composite Radius Fillers for Cure Distortion
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Solution Overview
Problem
Traditional composite radius fillers lack the ability to vary mechanical properties along their length, leading to potential distortion and mismatch with the composite structure during formation and curing, necessitating a need for composite radius fillers with variable mechanical properties.
Innovation Solution
Composite radius fillers are designed with a main-portion and an end-portion having different stiffnesses, where the interface between them forms an angle relative to the longitudinal axis, allowing for varying mechanical properties along the filler's length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional composite radius fillers with uniform material properties are used, then manufacturing is simple, but distortion occurs during formation and curing due to mismatch with composite structure
Solution Approach 1:
The composite radius filler is divided into multiple sections along its length, with each section having different material properties (stiffness, fiber orientation, resin content) tailored to match the local requirements of the composite structure at that position. This local variation in quality allows the filler to conform to the curved geometry and mechanical property gradients of the composite structure, preventing distortion during formation and curing.
Solution Approach 2:
The filler is segmented into multiple discrete sections or layers, each with independently controlled material properties. This segmentation enables precise control over the mechanical behavior at different locations along the filler, allowing it to adapt to the varying constraints imposed by the composite structure's geometry and curing process.
2Manufacturing precision
If composite radius filler geometry is closely matched to void space shape, then structural fit is improved, but manufacturing complexity increases
Solution Approach 1:
The filler's cross-sectional geometry and material properties are locally adapted to match the void space configuration at each position along its length. This local customization achieves precise geometric fit while the modular segmented structure keeps manufacturing complexity manageable through systematic variation rather than completely custom designs.
3Ease of manufacture
If uniform stiffness is used throughout the filler, then manufacturing is easier, but distortion occurs during composite structure curing
Solution Approach 1:
The filler incorporates sections with varying stiffness values along its length, with each section's stiffness locally optimized to match the mechanical properties of the adjacent composite structure. This gradient in stiffness prevents stress concentrations and distortion during curing, while the segmented architecture maintains manufacturing feasibility through modular construction.
Data Source
AI summary
Composite radius fillers and assemblies comprising composite radius fillers are disclosed. An example of a composite radius filler comprises a body having a longitudinal axis. The body comprises a main-portion and an end-portion. The main-portion extends along the longitudinal axis and has a first stiffness. The body further comprises an end-portion that extends along the longitudinal axis, that is adjacent to the main-portion, that defines at least a portion of a terminal end of the body, and that has a second stiffness that differs from the first stiffness. At least a first portion of an interface between the main-portion and the end-portion is at an angle relative to the longitudinal axis. Methods for a composite manufacturing method comprise constructing a composite radius filler. Aircraft assemblies comprising a composite radius filler are further disclosed.