Strain Gauge Integration in Aircraft Composite Structures
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Solution Overview
Problem
Existing methods for producing aircraft structures do not effectively integrate deformation sensors, limiting the ability to measure structural deformations directly during testing or operation.
Innovation Solution
A method involving the use of a deformable tubular sack within a mould to create a closed-section aircraft structure, where a strain gauge is permanently fastened to a flat tape and adhered to the structure's wall using a vacuum and heating cycle, allowing deformation measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If deformation sensors are integrated into the aircraft structure during production, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The strain gauge is prepared and permanently fastened to a flat tape before insertion into the mould. This preliminary preparation allows the sensor to be integrated into the structure during the normal production process rather than requiring post-production installation, thus improving measurement capability without significantly increasing overall device complexity
Solution Approach 2:
The flat tape carrying the strain gauge is inserted within the tubular sack during the autoclave process. The tape becomes nested within the composite structure walls as the sack expands and presses against the mould walls. This nesting approach integrates the sensor into the structure without adding external complexity
2Measurement precision
If a strain gauge is permanently fastened to a flat tape and adhered to the structure wall, then deformation transmission is improved, but manufacturing process complexity increases
Solution Approach 1:
The strain gauge, flat tape, and adhesive layer are combined into a single integrated assembly that is applied to the structure wall in one operation. The tape serves both as a mounting substrate and as the element that transmits deformation to the gauge, merging multiple functions into a single component system
Solution Approach 2:
The manufacturing process utilizes changes in temperature and pressure during the autoclave heating cycle to control the adhesive curing and sack expansion. By leveraging these parameter changes, the tape adheres firmly to the structure wall without requiring separate fastening operations, thus improving deformation transmission while managing manufacturing complexity
3Strength
If the tubular sack expands during heating cycle, then composite material fusion is improved, but sensor integration difficulty increases
Solution Approach 1:
The flat tape with the strain gauge is prepared and positioned on the tool before the autoclave heating cycle begins. This preliminary action ensures the sensor assembly is in place before the sack expands, allowing the expansion process to simultaneously bond the composite materials and secure the sensor integration in one coordinated operation
Solution Approach 2:
The tubular sack acts as an intermediary element that transfers the heating and pressure effects uniformly to both the composite materials and the flat tape. As the sack expands during heating, it presses against both the composite layers and the tape, facilitating simultaneous fusion and sensor adhesion without requiring separate processes
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
Enables the direct measurement of structural deformations applied to aircraft components, enhancing monitoring capabilities during testing and operation without altering the structure's rigidity.
Implementation Method 1
creating a vacuum in an autoclave inside which the mould is arranged to allow expansion of the sack, which presses against the walls of the cavity during a heating cycle in which the sheets of composite material fuse with each other
Implementation Method 2
during a heating cycle in which the sheets of composite material fuse with each other
Implementation Method 3
depositing an adhesive layer on the second face of said tape; inserting said tool supporting said tape in said cavity; creating a vacuum and performing a second heating cycle to obtain the expansion of said vacuum sack, which performs the pressure gluing of said tape onto a wall of said cavity
Data Source
AI summary
A method for producing a closed-section portion of an aircraft wherein a strain gauge is glued on a first face of a flat tape that, in turn, is fastened on a face of a tool comprising a rigid elongated body covered by an extensible sack. The tool supporting the tape is arranged in a cavity of an aircraft structure. A vacuum is then created to obtain the expansion of the vacuum sack and perform the pressure gluing of the tape onto a wall of said cavity. The tool is subsequently extracted from the cavity. Upon conclusion of these operations, the tape is integrally fastened onto a wall of the cavity so that any deformation applied to this wall is transmitted to said strain gauge.