Hat-Stiffened Composite Skin Manufacturing With Tapered Preforms
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Solution Overview
Problem
Existing methods for manufacturing composite structures, particularly in aircraft, face challenges in efficiently producing stiffened composite skins using blade stiffeners, which require in-tool or pre-infusion compaction to achieve target fiber volumes and weight targets, and there is a need for improved methods that reduce tooling costs and facilitate easier removal of cured parts.
Innovation Solution
A method involving the use of dry, hat-shaped preforms applied into a recess in a lower mold tool, combined with skin-preform layers, followed by resin infusion and curing, where the preforms are slightly tapered to facilitate easy removal and utilize reusable tooling to reduce costs and improve handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If blade stiffeners are used with in-tool or pre-infusion compaction, then target fiber volumes and weight targets are achieved, but tooling costs increase and part removal becomes difficult
Solution Approach 1:
The hat-shaped preform is pre-formed with a tapered geometry before placement in the mold. This preliminary shaping action allows the preform to be self-contained and self-positioning, eliminating the need for complex in-tool compaction mechanisms while ensuring proper fiber volume and weight targets are met.
Solution Approach 2:
Instead of using complex in-tool compaction to achieve proper fiber volume, the invention inverts the approach by pre-forming the stiffener with a tapered geometry that naturally achieves the target fiber volume without requiring additional compaction equipment or processes.
2Manufacturing precision
If blade stiffeners are used with in-tool or pre-infusion compaction, then target fiber volumes and weight targets are achieved, but part removal becomes difficult
Solution Approach 1:
The hat-shaped preform is pre-formed with a tapered geometry before placement in the mold. This preliminary shaping action creates a self-contained component that can be easily removed from the mold after curing, eliminating the part removal difficulties associated with blade stiffeners and in-tool compaction.
Solution Approach 2:
The hat-shaped preform features an asymmetric tapered geometry that is slightly tapered from the first end to the second end longitudinally. This asymmetric shape allows the preform to be easily removed from the mold in the direction of the taper, solving the part removal difficulty while maintaining structural integrity.
3Ease of operation
If dry, hat-shaped preforms with taper are used, then part removal becomes easy and tooling costs are reduced, but manufacturing complexity increases
Solution Approach 1:
The stiffener is segmented into a hat-shaped preform with distinct flanges and web sections. This segmentation allows the preform to be manufactured separately with optimized tapered geometry for easy removal, then assembled with the skin preform layers, reducing overall manufacturing complexity despite the specialized preform shape.
4Ease of manufacture
If dry preform assembly is used without pre-infusion compaction, then tooling costs are reduced, but fiber volume control becomes challenging
Solution Approach 1:
The hat-shaped preform is pre-formed with a tapered geometry that is designed to achieve the target fiber volume directly during the resin infusion process, without requiring pre-infusion compaction. This preliminary design of the preform geometry ensures proper fiber volume is achieved while reducing tooling costs.
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 enables efficient production of stiffened composite skins with reduced tooling costs, easier part removal, and robust stiffener/skin joints, while maintaining structural integrity and reducing peel stresses.
Implementation Method 1
Resin is infused into the dry preform assembly to form a resin-infused preform
Implementation Method 2
Resin is infused into the dry preform assembly to form a resin-infused preform
Implementation Method 3
The resin-infused preform is cured in situ to form the stiffened composite skin
Data Source
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AI summary
Stiffened composite skin (200) and methods of manufacture. A dry, hat-shaped preform (214) is applied into a recess (222) in a lower mold tool (218). A first set of dry, skin-preform layers (216) is applied over the dry, hat-shaped preform (214) to form a dry preform assembly (204). Resin (207) is infused (206, 808) into the dry preform assembly to form a resin-infused preform (210). The resin-infused preform is cured (208, 810) in situ to form the stiffened composite skin (200).