Multi-Hardness Joint Structure for Dissimilar Material Bonding
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Solution Overview
Problem
The bonding between members made of different materials, such as fiber reinforced plastic and metallic materials, experiences a decrease in strength due to cracks generated by the difference in deformation between the members, leading to reduced fatigue strength.
Innovation Solution
A joint structure is designed with a fit-in groove and an insertion section, featuring multiple bonding layers of varying hardness to mitigate the stress and deformation differences, including a softer bonding layer near the deepest section to suppress crack formation and a harder bonding layer for enhanced tensile strength, along with fiber-containing layers oriented differently to distribute loads effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If members made of different materials (fiber reinforced plastic and metallic materials) are bonded together, then the joint structure can achieve material complementarity and structural performance, but the bonding strength decreases due to cracks generated by deformation differences between the members
Solution Approach 1:
The bonding layer is divided into multiple regions with different hardness values. The region near the deepest section of the fit-in groove uses a softer bonding layer to accommodate deformation and suppress crack formation, while other regions use harder bonding layers to provide tensile strength. This local differentiation of material properties resolves the contradiction between material adaptability and bonding strength.
Solution Approach 2:
The bonding structure uses a composite of multiple bonding layers with different hardness characteristics. This composite bonding layer structure combines the advantages of both soft (crack suppression) and hard (tensile strength) materials, enabling the joint to simultaneously achieve adaptability to deformation differences and maintain high bonding strength.
2Ease of manufacture
If a single bonding layer is used between different material members, then the manufacturing process is simple, but cracks occur due to deformation differences reducing fatigue strength
Solution Approach 1:
The bonding layer is segmented into multiple regions with different hardness values based on their functional requirements. The softer region is positioned near the deepest section where deformation occurs, while harder regions are positioned elsewhere to provide strength. This segmentation approach maintains manufacturing feasibility while significantly improving fatigue strength by preventing crack propagation.
3Strength
If a harder bonding layer is used to increase tensile strength, then the bonding strength improves, but crack formation is promoted due to inability to accommodate deformation differences
Solution Approach 1:
Different regions of the bonding layer are assigned different hardness properties according to their specific functional needs. The softer bonding layer region is located near the deepest section of the fit-in groove where deformation occurs, allowing it to accommodate shape changes without cracking. Harder bonding layer regions are located in areas requiring tensile strength, providing structural integrity without promoting crack formation.
Data Source
AI summary
A joint structure includes a first member having a fit-in groove, a second member made of a material different from a material of the first member and having an insertion section to be inserted into the fit-in groove, and a plurality of bonding layers having different hardness and formed between the fit-in groove and the insertion section.