Composite Article Plydrop Machining for Stress Reduction
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Solution Overview
Problem
Existing composite laminates face issues with plydrops, which lead to resin-rich areas and local stress concentrations, damaging the mechanical properties of the composite article, especially when using multi-axial dry fibre fabrics.
Innovation Solution
The method involves stabilizing non-crimp fibre fabrics, machining the surface to create a smooth blended surface with chamfered plydrops, and positioning the machined article in a second mould for resin infiltration and curing, allowing for improved in-plane and torsional properties, and reducing the detrimental effects of plydrops on mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-axial dry fibre fabrics are used to form composite laminates, then formability and deposition speed are improved, but plydrop increases resulting in resin-rich areas and stress concentrations
Solution Approach 1:
The patent applies preliminary action by pre-machining the dry fibre preform article before resin infusion. The surface is machined to create a smooth blended surface with chamfered plydrops, eliminating binary plydrops in the interior. This preliminary machining action prepares the article for near-net shape moulding, reducing the need for post-curing machining and improving final geometric precision.
Solution Approach 2:
The patent changes the geometric parameters of the plydrops by machining them into chamfered shapes rather than leaving them as binary steps. This parameter change from vertical to chamfered transitions reduces stress concentration and eliminates resin-rich areas, while maintaining the productivity benefits of using multi-axial dry fibre fabrics.
2Ease of manufacture
If dry fibre based precursor materials are used instead of prepreg, then storage and handling requirements are simplified, but plydrop problems are enhanced
Solution Approach 1:
The patent applies preliminary action by performing surface machining on the dry fibre preform article before resin infusion. This eliminates binary plydrops in the interior and creates chamfered plydrops on the surface, thereby resolving the plydrop control issue while maintaining the ease of manufacture advantages of dry fibre materials.
Solution Approach 2:
The patent applies local quality by differentiating the treatment of plydrops based on their location. Interior binary plydrops are eliminated through machining, while surface plydrops are chamfered to reduce stress concentration. This localized quality control maintains the benefits of dry fibre materials while addressing plydrop issues differently in different regions.
3Manufacturing precision
If machining is performed on dry fibre composites, then surface geometry and leading/trailing edge accuracy are improved, but the flexible nature of fibre layers makes repeatable cutting difficult
Solution Approach 1:
The patent applies preliminary action by stabilizing the non-crimp fibre fabrics before machining. This stabilization creates a more rigid structure that enables repeatable cutting and machining operations, thereby improving ease of manufacture while maintaining the manufacturing precision benefits of machining dry fibre composites.
Data Source
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AI summary
A method of forming a composite article (100) involves the steps of: providing a formed article (43) , the formed article comprising a plurality of non-crimp fibre fabrics (120) with each non-crimp fibre fabric comprising at least two dry-fibre layers (122); stabilising the plurality of non-crimp fibre fabrics (120); machining a surface of the formed article having exposed ply terminations to provide a smooth blended surface with chamfered plydrops; positioning the machined formed article in a second mould (170); infiltrating the second mould (170) with a polymer matrix resin; and curing the machined formed article to form the composite article.