Co-curing Composite Stiffeners with Rigid and Flexible Mandrels
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Solution Overview
Problem
Existing methods for co-curing composite structures with stiffeners on both sides often result in defects due to pressure imbalances at stiffener intersections, leading to distortion or wrinkling of the center structure.
Innovation Solution
The use of substantially rigid mandrels on one side and flexible mandrels on the other side of the composite structure during co-curing, along with a rigid tool that defines troughs, helps to maintain even pressure and prevent distortion by providing dimensional constraints and flexibility, ensuring uniform pressure distribution at stiffener intersections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If co-curing is used to manufacture composite structures with stiffeners on both sides, then productivity is improved by consolidating multiple operations into one curing cycle, but manufacturing precision deteriorates due to pressure imbalances at stiffener intersections causing laminate distortion or wrinkling
Solution Approach 1:
The patent applies local quality by using different mandrel types (rigid vs. flexible) at different locations within the same structure. Rigid mandrels are placed at stiffener intersections where pressure control is critical, while flexible mandrels are used in panel areas where conformability is needed. This localized differentiation resolves the pressure distribution problem during co-curing while maintaining high productivity.
Solution Approach 2:
The patent changes the physical parameter of mandrel rigidity to control pressure distribution. By selecting mandrels with different rigidity parameters at different locations, the system achieves uniform pressure distribution across the structure during co-curing, eliminating distortion while maintaining the productivity benefits of consolidated manufacturing.
2Manufacturing precision
If rigid mandrels are used to maintain dimensional constraints during co-curing, then manufacturing precision is improved by preventing distortion, but device complexity increases due to the need for different mandrel types and configurations
Solution Approach 1:
The mandrel system is segmented into distinct rigid and flexible components that can be independently selected and positioned. This segmentation allows each mandrel type to perform its specific function optimally - rigid mandrels for dimensional control at critical intersections, flexible mandrels for conformability in panel areas - thereby achieving high precision without requiring a single complex mandrel design.
Solution Approach 2:
The system incorporates both static (rigid) and dynamic (flexible) mandrel elements. The rigid mandrels provide stable dimensional constraints, while the flexible mandrels can adapt their shape to accommodate curing shrinkage and pressure changes. This dynamic combination maintains dimensional accuracy while simplifying the overall system by allowing each mandrel type to be relatively simple in its own right.
Data Source
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AI summary
A method for manufacturing a cured composite structure from first stringers, second stringers and a panel comprising a first side and a second side, the method includes, for each first stringer, supporting the first stringer on the first side of the panel using a substantially rigid mandrel positioned within a first cavity defined between the first stringer and the first side of the panel, for each second stringer, supporting the second stringer on the second side of the panel using a flexible mandrel positioned within a second cavity defined between the second stringer and the second side of the panel, and co-curing the first stringers, the panel, and the second stringers while each of the one or more first stringers are supported by the respective substantially rigid mandrel and each of the one or more second stringers are supported by the respective flexible mandrel.