Thermoplastic Composite Panel Welded Stiffeners
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Solution Overview
Problem
Existing methods for manufacturing stiffened composite panels for aeronautics applications face challenges such as high manufacturing costs, quality defects, and increased mass due to the need for fasteners like rivets, which are not suitable for cross stiffening with continuous fibers and result in low peening resistance.
Innovation Solution
A double-sided stiffened composite panel made of thermoplastic matrix with continuous fiber reinforcement, where stiffeners are welded directly to the skin without fasteners, using a method that involves drape forming, integration of a miscible resin film, and consolidation to ensure strong bonding and resistance to buckling stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rivet type fasteners are used to assemble stiffeners to the skin, then cross stiffening can be achieved, but the mass of the panel increases and peening resistance decreases
Solution Approach 1:
The invention extracts and eliminates the fastening elements (rivets and cleats) from the assembly process. By using thermoplastic resin-impregnated continuous fibers that are co-cured with the skin, the stiffeners are integrated directly into the panel structure without requiring separate fastening components, thereby reducing mass while maintaining cross stiffening capability
Solution Approach 2:
The invention merges the stiffener assembly process with the skin manufacturing process. Both the skin and stiffeners are made from thermoplastic resin-impregnated continuous fibers and co-cured in a single autoclave cycle, creating an integrated monolithic structure that eliminates the need for separate fastening operations
2Strength
If multiple distinct assembly steps are used to manufacture the panel, then cross stiffening can be achieved, but manufacturing cost increases and quality defects increase
Solution Approach 1:
The invention combines multiple manufacturing operations into a single autoclave curing cycle. The skin and all stiffeners are pre-consolidated with thermoplastic resin and then co-cured together in one continuous process, eliminating separate assembly steps for attaching stiffeners and reducing opportunities for quality defects
Solution Approach 2:
The invention performs preliminary consolidation of the skin and stiffeners with thermoplastic resin before the final curing operation. This pre-consolidation step ensures that all components are properly positioned and bonded before autoclave curing, simplifying the overall manufacturing process and reducing the need for post-assembly operations
3Strength
If continuous orthogonal stiffeners are placed on both sides of the skin, then cross stiffening can be achieved without fasteners, but manufacturing quality defects increase due to handling non-consolidated pre-forms
Solution Approach 1:
The invention performs preliminary consolidation of the skin and stiffeners with thermoplastic resin before final curing. This pre-consolidation step stabilizes the pre-form structure, making it easier to handle during the turning and assembly operations while maintaining the ability to achieve cross stiffening with continuous fibers on both sides
Solution Approach 2:
The invention changes the physical state of the resin from a consolidatable pre-form state to a fully cured monolithic state through controlled heating in the autoclave. This parameter change (temperature and pressure application) transforms the material properties to enable easy handling during manufacturing while ensuring high-quality final bonding without defects
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 allows for a single-step assembly of double-sided composite panels with improved resistance to buckling and reduced manufacturing defects, while maintaining fire and impact resistance, and is suitable for aeronautics applications without the need for fasteners, thus reducing mass and increasing efficiency.
Implementation Method 1
raise the temperature of the material to a temperature that is at least equal to the melting temperature of the resin
Implementation Method 2
said stiffeners are closely joined to the skin by welding
Data Source
AI summary
A stiffened panel and method for producing such a panel comprising a laminated skin extending in two directions, made of a resin and a continuous fibers reinforcement. A first stiffener in the form of a beam is made of a resin with continuous fibers reinforcement and extends on a first side of the laminated skin in a first direction. A second stiffener in the form of a beam is made of a resin with continuous fibers reinforcement and extends on a second side of the laminated skin in a second direction. The resins which make up the skin and the stiffeners are thermoplastic in nature and the stiffeners are closely joined to the skin by welding.