Oriented Structural Adhesive Gap Bridging
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Solution Overview
Problem
Heat activatable structural adhesives face challenges in bridging gaps between components without introducing porosity, which reduces their strength and stiffness, and they struggle to bond dissimilar materials like steel and aluminum that cannot be welded.
Innovation Solution
A dry, heat-activatable structural adhesive formulation that utilizes orientable polymer systems capable of changing shape upon heating, allowing for thickness increase to bridge gaps and develop adhesive properties, eliminating the need for porosity and enabling bonding of dissimilar materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If foamable structural adhesives are used to fill gaps between members, then the adhesive can expand to fill the gap and bond the members together, but the foamed structure reduces the strength and stiffness of the structural adhesive by introducing porosity
Solution Approach 1:
The patent changes the physical state of the adhesive from a foamed structure to a dense solid structure by using a thermoplastic polymer that undergoes solid-to-solid phase transition when heated. This allows the adhesive to increase in thickness through solid-state expansion rather than foam formation, maintaining strength while achieving gap filling capability
Solution Approach 2:
The patent uses a composite formulation combining a thermoplastic polymer (for shape change and gap bridging) with a thermosetting polymer (for adhesive bonding). This composite approach allows the adhesive to achieve both thickness increase and high strength without porosity, resolving the contradiction between volume expansion and strength maintenance
2Strength
If conventional heat activatable structural adhesives are used, then they can bond dissimilar materials like steel and aluminum, but they cannot increase in thickness to bridge gaps between components
Solution Approach 1:
The patent introduces dynamic shape-changing capability to the adhesive by using a thermoplastic polymer that undergoes reversible solid-to-solid phase transition when heated. This allows the adhesive to dynamically increase in thickness in response to temperature changes, enabling gap bridging while maintaining bonding strength through the thermosetting polymer component
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 adhesive achieves significant thickness increase (25% to 500%) upon heating, providing strong, stiff bonds between dissimilar materials without porosity, reducing the need for welding and enhancing structural integrity in automotive and aircraft applications.
Implementation Method 1
A dry, heat-activatable structural adhesive formulation that utilizes orientable polymer systems capable of changing shape upon heating, allowing for thickness increase to bridge gaps
Implementation Method 2
which shrinks in at least one direction and increases in thickness in a transverse direction when heated to a temperature between the first and second temperatures
Data Source
AI summary
A solid, dry to the touch at ambient temperature, heat curable, generally non-foaming structural adhesive that exhibits shape memory characteristics. The adhesive can be cured at an elevated temperature and contains a high molecular weight polymeric constituent that can be oriented such that at an elevated temperature below the curing temperature the material will shrink in one plane while increasing its thickness at a temperature in the range of from above the elevated temperature to below the curing temperature.