Multi-Material Joint Sealant for Galvanic Insulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The joining of dissimilar materials in vehicle body structures, such as steel and lightweight metals, poses challenges due to galvanic corrosion and the brittleness of traditional structural adhesives, which lack flexibility and elongation, making them unsuitable for multi-material joints with fasteners.
Innovation Solution
A multi-material joint is created using a sealant comprising liquid elastomers and foaming agents, optionally with epoxy resins, that expands by 15-35% post-cure, providing tensile shear strength of less than 1 MPa and galvanic insulation between steel and lightweight metal or metal alloy components, allowing for flexible and corrosion-resistant bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If structural adhesives are used to produce load-bearing joints between dissimilar materials, then the joints achieve high tensile shear strength, but the adhesives become brittle and offer little flexibility or elongation, requiring additional safeguards against environmental penetration and corrosion
Solution Approach 1:
The patent changes the physical and chemical parameters of the adhesive material by incorporating liquid elastomers (providing flexibility and elongation) combined with foaming agents (creating cellular structure). This transforms the adhesive from a brittle solid into a flexible, expandable material that maintains bond strength while providing environmental protection through its elastic properties and ability to accommodate thermal expansion and contraction.
Solution Approach 2:
The invention creates a composite sealant material combining liquid elastomers with foaming agents and optionally epoxy resins. This composite structure integrates the flexibility and adhesion of elastomers with the structural properties of foam, producing a material that simultaneously achieves tensile shear strength greater than 1 MPa while maintaining elongation and flexibility to protect against environmental penetration.
2Weight of moving object
If lightweight materials are substituted for steel in vehicle body structures, then vehicle mass is reduced, but additional processes are required to inhibit galvanic corrosion at dissimilar material joints
Solution Approach 1:
The expandable sealant acts as an intermediary material between dissimilar metals (steel and lightweight metals). The sealant contains corrosion inhibiting additives that form protective barriers at the metal interface, electrically isolating the dissimilar materials and preventing galvanic corrosion currents. This single intermediate layer eliminates the need for additional corrosion protection processes such as galvanizing or anodizing.
Solution Approach 2:
The patent applies local quality by concentrating corrosion protection exactly where needed—at the joint interface between dissimilar materials. The sealant formulation includes corrosion inhibitors and rust preventatives that are locally applied at the critical interface zone, providing targeted protection without requiring complex multi-step surface treatment processes on the entire vehicle body.
3Reliability
If traditional sealants are used in multi-material joints with fasteners, then the joints lack sufficient flexibility and elongation, but the patent's sealant achieves tensile shear strength greater than 1 MPa with improved flexibility and elongation
Solution Approach 1:
The patent fundamentally changes the rheological parameters of the sealant by using liquid elastomers as the base material. This provides inherent flexibility and elongation properties. The addition of foaming agents creates a cellular structure that further enhances elasticity and ability to deform without breaking, while the liquid state before curing allows for easy application and penetration into joint gaps.
Solution Approach 2:
The composite formulation combines liquid elastomers (for flexibility and elongation) with foaming agents (for cellular structure and cushioning) and optionally epoxy resins (for adhesion and strength). This composite achieves the synergistic effect of maintaining tensile shear strength greater than 1 MPa while providing superior flexibility and elongation compared to traditional rigid sealants.
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 inhibits galvanic corrosion and maintains structural integrity by providing flexible insulation and improved corrosion protection in multi-material joints, outperforming traditional structural adhesives in salt spray tests.
Implementation Method 1
The sealant comprises one or more liquid elastomers, one or more foaming agents, and optionally one or more epoxy resins. Optionally, the sealant has a post-cure volume that is 15-35% greater than a pre-cure volume of the sealant.
Implementation Method 2
A sealant is positioned between the first member and the second member that galvanically insulates the first member from the second member.
Data Source
AI summary
A multi-material joint and a method of making thereof. The multi-material joint includes a first member comprising a first metal or metal alloy that is secured to a second member comprising a second metal or metal alloy that is different than the first metal or metal alloy. A sealant is positioned between the first member and the second member that galvanically insulates the first member from the second member. The sealant comprises a liquid elastomer and a foaming agent.