Self-Piercing Rivet Joining Composite Parts
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Solution Overview
Problem
Composite materials like carbon fiber and glass fiber composites face challenges in joining due to limited ductility, leading to surface cracking and fiber exposure, which reduces joint durability and requires costly assembly methods like drilling for blind rivets.
Innovation Solution
A self-piercing rivet method using a riveting tool with a punch and die, where a composite part with a fiber-reinforced resin matrix layer and a non-fiber reinforced resin matrix layer are used, allowing the rivet to penetrate partially into the second layer without exposing the filler material, and a textured surface on the compression molding die prevents fiber exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If self-piercing rivet is used to join composite parts, then high-volume production and mechanical interlock are achieved, but surface cracking and fiber exposure occur due to limited ductility
Solution Approach 1:
A smooth button surface is formed on the composite part before the riveting operation by pre-forming a recess or cavity in the composite material at the location where the button will form. This preliminary action prepares the structure to accommodate the deformation without causing surface cracking or fiber exposure during the riveting process.
Solution Approach 2:
The physical state or geometry of the composite material is modified by creating a pre-formed recess or cavity that changes the local deformation characteristics. This parameter change allows the material to undergo the necessary deformation for mechanical interlock without exceeding its ductility limits and causing surface damage.
2Strength
If blind rivets are used to fasten parts to composite components, then joining is achieved, but assembly cost and tooling cost increase due to additional drilling and alignment operations
Solution Approach 1:
The drilling and hole preparation operations are eliminated from the joining process. The self-piercing rivet method extracts the unnecessary preliminary steps (drilling, alignment) while retaining the essential function of mechanical fastening, thereby reducing assembly cost and tooling requirements.
Solution Approach 2:
The self-piercing rivet performs its own installation function by piercing the composite material directly without requiring pre-drilled holes. The rivet serves both as the fastening element and the installation tool, eliminating the need for separate drilling and alignment operations.
3Strength
If adhesive is used to join composite parts, then joining is achieved, but production volume is limited and displacement occurs before curing
Solution Approach 1:
The chemical bonding mechanism of adhesive is replaced with a mechanical fastening system using self-piercing rivets. This substitution enables immediate structural integrity without curing time, allowing for high-volume production while eliminating the displacement issue that occurs with adhesive before curing.
Data Source
AI summary
A method of joining parts together with a self-piercing rivet that is inserted through a part and partially through a second part. The second part includes a fiber-filled layer and a resin matrix layer that together form a composite part. A self-piercing rivet extends into the second part, but does not penetrate completely through the matrix layer. An assembly, including a first part and a second part that includes a reinforced layer and a resin layer in which a fastener is inserted, but does not extend through the second layer. A composite part including a first layer of resin matrix reinforces the filler and a second layer of resin matrix that does not include a filler and is more than 3 microns thick.