Pyrotechnic Separation Device for Composite Assemblies
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Solution Overview
Problem
Existing devices for temporary connection and pyrotechnic separation in the aeronautical and space industries generate high shock levels and pollution when cutting composite materials, which can be detrimental to surrounding systems.
Innovation Solution
A device that uses a pyrotechnic expansion tube to detach only the outer layers of a composite material, with a bonding surface smaller than the internal layers, and incorporates an elastomeric material for shock absorption, reducing shock and pollution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pyrotechnic charge is used to cut the material forming the connection between two coupled assemblies, then the connection is separated, but very high shock levels are generated which are detrimental to neighboring elements such as floors, equipment and payload
Solution Approach 1:
The invention extracts only the outer layers (fusible plies) of the composite material for detachment, rather than cutting through the entire connection structure. This selective removal of material reduces the energy release and consequently the shock levels generated during separation, while still achieving reliable detachment of the assemblies.
Solution Approach 2:
The composite material is segmented into fusible outer layers and non-fusible inner layers. The pyrotechnic charge is designed to affect only the fusible layers, creating a segmented separation process where the harmful effects are contained to a smaller portion of the material, reducing overall shock transmission to surrounding elements.
2Object-affected harmful factors
If the pyrotechnic charge is reduced to lower shock levels, then neighboring elements are protected, but the separation force may be insufficient to detach the connection
Solution Approach 1:
The invention applies local quality by creating fusible layers with specific material properties (lower melting point, easier detachment) only in the regions where separation is needed. This localized material modification allows the pyrotechnic charge to generate sufficient separation force with reduced energy, as the fusible layers require less force to detach compared to the full composite structure.
3Object-affected harmful factors
If a strip is used to connect two sets and is detached by pyrotechnic expansion, then shock levels are reduced, but if the material is composite, there is a risk of tearing of layers causing pollution detrimental to surrounding systems
Solution Approach 1:
The invention changes the material parameters of the outer layers by making them fusible, which fundamentally alters their separation behavior. Instead of tearing (which generates pollution), the fusible layers melt and detach cleanly under the pyrotechnic expansion, eliminating fiber pollution while maintaining low shock levels.
4Object-affected harmful factors
If shock dissipating devices are provided to reduce shock levels, then neighboring elements are protected, but the mass of the assembly increases
Solution Approach 1:
The invention replaces the mechanical shock dissipation system with a material-based solution. Instead of adding mechanical devices to absorb or dissipate shock, the fusible layers are designed to separate with inherently lower shock generation, substituting a mechanical approach with a material property-based approach that reduces both shock and mass.
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
The solution effectively reduces shock levels and pollution by peeling off the outer layers of composite materials during separation, minimizing damage to surrounding systems and reducing the mass and size of the separation device.
Implementation Method 1
A pyrotechnic expansion tube is arranged in a housing provided at the level of the connection, and causing, due to the shock wave transmitted to the strip, the take-off of the strip from one of the sets.
Implementation Method 2
the bonding surface of the part of the layer(s) intended to be separated from the rest of the stack is lower than the bonding surfaces between the internal layers between them
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~4
AI summary
The invention relates to a device for temporary connection with a longitudinal axis (X) and for pyrotechnic separation, including a pyrotechnic expansion tube (14) mounted in a space (11) arranged in a connection area between a first (2) and a second (4) assembly to be separated, the second assembly (4) consisting of a stack of layers (12.1, 12.2) adhered to one another, the two assemblies (2, 4) being connected together by two metal parts (10.1, 10.2), said metal parts being attached to the first assembly and adhered to the outer layers (12.1) of the second assembly (4), wherein the adhesion surface between said outer layer (12.1) and the adjacent inner layer (12.2) is smaller than the adhesion surface between two inner layers (12.2) forming a fusible layer, such that, when the pyrotechnic expansion tube (14) is used, the outer layer (12.1) separates from the adjacent inner layer.