Bladderless Hat Stringer Curing via Conformal Surface
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Solution Overview
Problem
The manufacturing of composite hat stringers for aircraft structures is complex and costly, with fiber-reinforced composite materials presenting challenges such as increased complexity, expense, and waste generation due to improper curing.
Innovation Solution
A method involving the use of a rigid mold line conformal surface for coupling and curing composite hat stringers with a skin, applying pressure to compress the skin against the stringer, and using a bladder for compressive pressure during curing to form a reinforced composite structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If fiber-reinforced composite materials are used to form structural members, then weight is reduced and mechanical strength is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The composite structure is divided into distinct modular components: hat stringers with rigid mold line conformal surfaces, skin panels, and adhesive bonding zones. This segmentation allows each component to be manufactured and cured independently before assembly, reducing overall manufacturing complexity while maintaining the weight and strength benefits of composite materials
Solution Approach 2:
The hat stringers are pre-cured to form rigid mold line conformal surfaces before the skin panels are applied. This preliminary action creates ready-to-bond surfaces with precise geometric features, eliminating the need for complex real-time shaping during assembly and reducing manufacturing complexity
2Strength
If pressure is applied to compress the skin against the hat stringer during curing, then bonding strength is improved, but additional equipment and process complexity are required
Solution Approach 1:
A bladder positioned within the hat stringer cavity is inflated with fluid pressure during the curing process. This pneumatic system applies uniform compressive force against the skin panel from the interior of the hat stringer, ensuring optimal bonding strength without requiring complex external mechanical pressing equipment
Solution Approach 2:
The bladder is nested within the hat stringer cavity, allowing the pressure application mechanism to be contained within the structure itself rather than requiring external equipment. This nested arrangement simplifies the overall system while maintaining effective bonding pressure
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 simplifies the manufacturing process, reduces costs, and integrates the stringer and skin structure more effectively, while minimizing waste and improving mechanical strength.
Implementation Method 1
applying pressure on the skin opposite the closed hat stringer to compress the skin against the closed hat stringer
Implementation Method 2
curing the skin to the rigid mold line conformal surface
Data Source
AI summary
Techniques for manufacturing structures that include composite hat stringers are disclosed. In one embodiment, a method of forming a composite structure includes placing a generally cured composite hat stringer on a tool, the hat stringer having a rigid mold line conformal surface for adjoining a generally uncured skin, positioning the skin adjacent to the rigid mold line conformal surface, coupling the skin to the rigid mold line conformal surface of the composite hat stringer, including applying a pressure to a surface of the skin to urge the skin into engagement with the composite hat stringer, and curing the skin.