Out-of-Autoclave Adhesive Shear Bonding for Composite Structures
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Solution Overview
Problem
Adhesive bonding of composite structural members in aerospace structures often requires heat and pressure, which is not feasible in all cases due to size or geometry constraints, and can be undesirable for heat-sensitive materials, limiting the use of autoclave curing methods.
Innovation Solution
A shear bonding method that uses conductive heating tiles to control adhesive viscosity and apply mechanical pressure through a bayonet-type tool, allowing for bonding in an out-of-autoclave environment by translating frames relative to a tapered tailboom skin to create a uniform adhesive bondline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If autoclave curing is used to achieve adhesive bonding, then bond quality is improved, but applicability deteriorates due to size and geometry constraints
Solution Approach 1:
The patent replaces the autoclave mechanical system with a combination of conductive heating elements and vacuum bagging system. The heating elements are positioned in direct contact with the adhesive bondline, eliminating the need for autoclave chamber while achieving equivalent curing temperatures and pressures through localized thermal and vacuum application.
Solution Approach 2:
The patent applies heating elements specifically at the adhesive bondline locations rather than heating the entire structure uniformly. This localized heating approach allows curing of large or complex geometries that cannot fit in an autoclave, as only the critical bonding areas require elevated temperature and pressure.
2Reliability
If autoclave curing is used to achieve adhesive bonding, then bond quality is improved, but process complexity deteriorates due to vacuum bag installation requirements
Solution Approach 1:
The patent positions conductive heating elements and applies adhesive to the bond surfaces before assembly, preparing the bonding interface in advance. This preliminary preparation simplifies the actual bonding process, as the heating elements are already in place to provide localized thermal energy during curing.
3Reliability
If autoclave curing is used to achieve adhesive bonding, then bond quality is improved, but suitability deteriorates for heat-sensitive materials
Solution Approach 1:
The patent applies heating elements only at the adhesive bondline locations rather than heating the entire structure uniformly. This localized heating approach allows curing of large or complex geometries that cannot fit in an autoclave, as only the critical bonding areas require elevated temperature and pressure.
Solution Approach 2:
The patent uses conductive heating elements as intermediaries to transfer thermal energy directly to the adhesive bondline through thermal conduction. This intermediary approach allows precise temperature control at the bondline while minimizing heat exposure to adjacent heat-sensitive materials, enabling curing of adhesives with lower temperature requirements.
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 achieves autoclave-quality bonds without an autoclave, utilizing high-temperature cure adhesive films and generating pressure through shearing angles and interfering fits, enabling bonding of large composite structures efficiently.
Implementation Method 1
A shear bonding method that uses conductive heating tiles to control adhesive viscosity
Implementation Method 2
generating pressure through shearing angles and interfering fits
Data Source
AI summary
The shear bonding method is configured to facilitate bonding of structures in an out-of-autoclave environment. The shear bonding method includes bonding a plurality of frame members to the interior of a tapered tailboom. The frames are located on a bayonet type tool. An adhesive pack is applied to each frame. The bayonet type tool is inserted into the tailboom until the adhesive packs come into contact with the interior walls of the tailboom. Conductive heating tiles are applied to the tailboom. The conductive heating tiles are controlled to achieve and maintain viscosity of the adhesive packs. During this period the bayonet tool is actuated so that the frames are translated in relation to the tailboom. The heating tiles are then controlled to achieve and maintain the adhesive at a requisite curing temperature.