Net-Shape Composite Stringer Joggle Forming with Interchangeable Shims
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Solution Overview
Problem
The production of composite stringers with out-of-plane features, such as joggles, is challenging due to stress concentrations that lead to undesired ply wrinkling and resin pooling, necessitating rework and material discard.
Innovation Solution
A method and apparatus using a punch, die, and interchangeable shims to form composite stringers to net shape, reducing wrinkling and resin pooling by simultaneously forming the stringer and out-of-plane features with a family of shims that adapt a single forming tool to produce various features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If out-of-plane features such as joggles are formed in composite stringers using a punch and die, then the stringer contains the required geometric features, but stress concentrations are generated that cause ply wrinkling and resin pooling
Solution Approach 1:
The invention applies preliminary action by forming the out-of-plane features during the initial stringer formation process rather than as a secondary operation. The punch is designed with varying thickness to pre-establish the required geometric features (such as joggles) while the stringer is being formed to its final cross-sectional shape, preventing stress concentrations and associated defects
Solution Approach 2:
The invention changes the parameter of the forming tool (punch) by varying its thickness along the length to match the desired out-of-plane features. This parameter change allows the punch to simultaneously form both the stringer's cross-sectional shape and the required geometric features like joggles, eliminating the need for secondary forming operations that cause stress concentrations
2Adaptability or versatility
If a single punch is used to form different out-of-plane features, then tooling versatility is improved, but the complexity of the punch design increases
Solution Approach 1:
The invention applies universality by designing a single punch that can form multiple different out-of-plane features through interchangeable components. The punch assembly includes a base punch and removable shim components that can be configured in different arrangements to create various geometric features, allowing one tool to perform multiple forming functions
Solution Approach 2:
The invention applies segmentation by dividing the punch into modular components - a base punch structure and separate shim elements that can be independently configured. This segmentation allows different shim arrangements to be used with the same base punch, providing versatility without requiring completely different punches for each feature type
Data Source
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AI summary
A tool is configured to form a composite charge into a stringer having a net shape with at least one out-of-place feature. The out-of-plane feature is formed by a shim removably attached to the tool. A family of the shims may be used to form a range of out-of-plane features having varying characteristics.