Thermoplastic Composite Stiffener Integration Without Extra Thermal Cycling
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Solution Overview
Problem
Existing methods for integrating stiffeners into thermoplastic polymer matrix composite parts require additional thermal cycling and complex tooling due to mismatched melting temperatures of polymers, leading to inefficiencies and shape discrepancies, especially for complex and large panels.
Innovation Solution
A method involving non-consolidated preforms of substrate parts and stiffeners, using a first thermoplastic polymer miscible with a second polymer at a higher melting point, allowing consolidation at a temperature below the second polymer's melting point to weld the flange onto the substrate, eliminating thermal cycling and simplifying tooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermoplastic films with lower melting temperature are used to assemble stiffeners with the skin, then the assembly can be carried out without deconsolidating the skin or stiffeners, but the large difference in melting temperatures does not ensure polymer miscibility at the interface and the rigid consolidated state prevents shape adaptation
Solution Approach 1:
The invention changes the temperature parameter by heating the assembly to a temperature between the glass transition temperature and melting temperature of the skin matrix polymer. This temperature range is higher than the prior art, allowing the skin matrix to soften and adapt to shape differences while remaining below the stiffener matrix melting point to maintain stiffener rigidity. This resolves the contradiction by enabling shape adaptation without compromising assembly effectiveness.
Solution Approach 2:
The invention introduces dynamic temperature control during assembly, heating the skin matrix to a semi-solid state where it can flow and adapt to shape differences, then cooling it to restore rigidity. This dynamic approach allows the skin to transition from rigid to adaptable and back, resolving the contradiction between maintaining rigidity and enabling shape adaptation.
2Ease of manufacture
If additional thermal cycling is performed to carry out the assembly, then the stiffeners can be assembled with the skin, but the process complexity and time increase
Solution Approach 1:
The invention merges the assembly operation with the skin consolidation process by performing both simultaneously in a single heating cycle. The skin is heated to its glass transition temperature range, allowing it to flow and bond with the stiffeners while the stiffeners are positioned and pressed into place. This eliminates the need for separate thermal cycling steps, reducing both process complexity and time while maintaining assembly effectiveness.
3Reliability
If complex tooling is used to apply uniform pressure in all directions for co-consolidation, then the skin and stiffeners can be consolidated together, but the device complexity increases
Solution Approach 1:
The invention performs preliminary positioning of the stiffeners on the skin before consolidation, and uses a simple unidirectional pressing tool to apply pressure during heating. The skin's own viscosity and the heated state provide the necessary flow characteristics for consolidation without requiring complex multi-directional pressure application. This preliminary positioning combined with simple unidirectional pressing achieves reliable consolidation while minimizing tooling complexity.
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 method enhances productivity and simplifies tooling by eliminating thermal cycling and ensuring shape adaptation without deconsolidation, while maintaining structural integrity and rigidity of the stiffeners.
Implementation Method 1
heating under pressure up to a first temperature that is higher than the first melting temperature range but lower than the second melting temperature range in order to consolidate the preform of the substrate part and to weld the flange of the stiffener on the substrate part
Implementation Method 2
heating under pressure up to a first temperature that is higher than the first melting temperature range but lower than the second melting temperature range in order to consolidate the preform of the substrate part and to weld the flange of the stiffener on the substrate part
Implementation Method 3
the first thermoplastic polymer is miscible with the second thermoplastic polymer at the second melting point
Data Source
AI summary
The invention pertains to a composite part with a fibrous reinforcement and a thermoplastic polymer matrix, comprising:substrate part with a matrix of a first thermoplastic polymer having a first melting temperature;stiffener made of a composite material with a matrix of a second thermoplastic polymer having a second melting temperature; comprising the steps of:obtaining an unconsolidated preform of the substrate part;obtaining a preform of the stiffener;integrating a layer of the first thermoplastic polymer into the preform of the stiffener at a location configured to be in contact with the substrate part; andsubjecting the substrate part and the preform of stiffener to a thermomechanical cycle so as to consolidate the substrate part and weld the stiffener to the substrate part.