Composite Tube Node Co-Molding for Seamless Joints
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Solution Overview
Problem
Current methods for manufacturing composite tube nodes in vehicular applications, such as bicycles and motorcycles, are slow, expensive, and aesthetically unpleasing due to the use of connector elements that require additional tooling and result in weak connections with visible steps at joints.
Innovation Solution
A process involving a multi-part mandrel within a mold cavity, where the mandrel is used to form a composite node element, and tube-skeletons with foam cores and fiber-containing fabrics are inserted and bonded with resin material, eliminating the need for additional tooling and creating a seamless joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If connector elements are used to join composite tubes, then the tubes can be assembled, but the connection strength is reduced and visible steps are created at joints
Solution Approach 1:
The invention removes the connector element from the joint assembly by creating an integrated monolithic structure where the node and tube elements are formed as a single continuous composite piece, eliminating the need for separate connectors and their associated weaknesses
Solution Approach 2:
The node element and tube elements are merged into a single integrated composite structure formed through co-molding, where the resin and fibers continuously flow from the node into the tube elements, creating a unified structural component rather than assembled parts
2Ease of manufacture
If connector elements are used to join composite tubes, then the tubes can be assembled, but additional tooling is required and manufacturing cost increases
Solution Approach 1:
The molding process for the node element and tube elements is merged into a single co-molding operation, eliminating the need for separate molding and assembly tooling, and reducing the number of manufacturing steps and equipment required
Solution Approach 2:
The tube elements are pre-formed and positioned within the mold cavity before the final curing stage, allowing them to be integrated into the node element during the same molding cycle without requiring additional assembly tooling
3Ease of manufacture
If connector elements are used to join composite tubes, then the tubes can be assembled, but the manufacturing process becomes slower
Solution Approach 1:
The formation of the node element and tube elements is combined into a single co-molding process that occurs simultaneously in one continuous operation, eliminating the sequential steps of separate molding, curing, and assembly operations
Solution Approach 2:
The resin injection and fiber placement continue uninterrupted from the node element formation through the tube element formation, maintaining continuous material flow and curing without interruption to maximize manufacturing efficiency
4Strength
If an entire composite frame is fabricated as a single part, then connection strength is improved, but the process becomes labor intensive and requires complex specialized tooling
Solution Approach 1:
The frame is segmented into modular components (node elements and tube elements) that are formed as an integrated unit through co-molding, allowing for easier handling and assembly of smaller manageable pieces while maintaining the strength benefits of a monolithic structure
Solution Approach 2:
The mold cavity is designed with flexible or adjustable components that can adapt to different frame configurations, allowing the same basic tooling to produce various frame designs without requiring completely specialized molds for each application
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 reduces tooling requirements, strengthens the connections, and eliminates the need for adhesives, resulting in a more efficient and aesthetically pleasing manufacturing process for composite tube nodes.
Implementation Method 1
injecting a resin material into the mold cavity such that the resin material permeates through the fiber-containing fabric and into an interior of the node element
Implementation Method 2
curing the composite material with the multi-part mandrel in place
Data Source
AI summary
A process includes disposing a mandrel assembly within a mold cavity bounded by mold forming surfaces. The mold is closed, first portions of the mandrel assembly seal against mold forming surfaces, and a continuous volume shaped as a node element is defined between second portions of the mandrel and the mold forming surfaces. A composite material is injected into the mold cavity filling the continuous volume, and cured forming the node element. The mandrel assembly is removed in sections exposing a node element opening. Tube-skeletons are inserted one each into openings of the node element, each tube-skeleton comprises foam core supported glass or carbon fabric materials. A resin material is injected into the mold cavity, such that the resin material permeates through the fabric material into a node element interior via the openings. The injected resin material is cured, thereby forming tube elements joined to the node element.