Radius filler for wet composite layup stiffness matching
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Solution Overview
Problem
Conventional methods for manufacturing composite structures with radius fillers are labor-intensive, time-consuming, and result in mismatched axial stiffness between the radius filler and the composite base member, leading to undesirable strength characteristics, particularly at the terminal ends of composite stringers.
Innovation Solution
A method involving the placement of a radius filler element made of dry fiber material into a composite base member's radius cavity, followed by infusion and chemical reaction with resin to create a hardened mixture that bonds the filler to the base member, ensuring a cured composite structure with improved strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual strips of prepreg composite material are laid up ply-by-ply into the radius cavity, then the radius filler can be manufactured, but the process becomes labor-intensive and time-consuming
Solution Approach 1:
The invention pre-fabricates the radius filler as a complete component before installation into the radius cavity. This preliminary action eliminates the need for on-site ply-by-ply assembly, significantly reducing labor intensity and manufacturing time while maintaining precise dimensional requirements for the radius filler.
2Manufacturing precision
If unidirectional reinforcing fibers are used in the radius filler, then the radius filler can be manufactured, but the axial stiffness of the radius filler becomes too high relative to the composite base member
Solution Approach 1:
The invention changes the fiber orientation parameter from unidirectional (0 degrees) to multi-directional arrangements including +45 degrees and -45 degree plies. This parameter change reduces the axial stiffness of the radius filler to better match the composite base member, preventing stress concentrations and improving overall structural strength while maintaining the required structural properties.
3Strength
If a laminating machine is used to laminate composite plies with non-zero degree fiber orientations, then the axial stiffness of the radius filler can be matched with the composite base member, but the capital expense for construction, operation, and maintenance increases significantly
Solution Approach 1:
The invention applies local quality by using different fiber orientations specifically in the radius filler component where stiffness matching is critical, rather than requiring expensive laminating machinery for the entire structure. The radius filler incorporates +45 and -45 degree plies locally to achieve proper stiffness characteristics, while the rest of the composite base member can be manufactured using conventional, more cost-effective methods.
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
This approach reduces the risk of cracking and enhances the strength and durability of the composite structure by matching the axial stiffness of the radius filler with the base member, while also being more efficient and cost-effective by eliminating the need for expensive laminating machines.
Implementation Method 1
infusing resin into the dry fiber material, and chemically reacting the resin with the radius filler material to create a mixture of resin and radius filler material
Implementation Method 2
allowing solvent in the resin to evaporate causing hardening of the mixture and bonding of the radius filler element to the composite base member
Data Source
AI summary
A method of manufacturing a cured composite structure includes placing a radius filler element into a radius cavity extending along a length of a composite base member formed of dry fiber material comprised of reinforcing fibers. The radius filler element is formed of a radius filler material. The method also includes infusing resin into the dry fiber material, and chemically reacting the resin with the radius filler material to create a mixture of resin and radius filler material along side surface interfaces between the radius filler element and the composite base member. The method additionally includes curing or solidifying the resin, and allowing solvent in the resin to evaporate causing hardening of the mixture and bonding of the radius filler element to the composite base member, and resulting in a cured composite structure.