Composite Joint Structure With Dovetail Locking Under Tensile Load
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Solution Overview
Problem
Existing composite joint members fail to maintain a stable joined state under tensile loads, particularly when the fiber direction of reinforcement fibers aligns with the load direction, leading to potential breakage and complexity in adhesive application.
Innovation Solution
A joint structure comprising joint members with projecting and recessed parts having dovetail shapes, oriented anisotropically to withstand tensile loads, where the fitting direction differs from the load direction, and optionally incorporating energy directors or adhesives for enhanced strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If reinforcement fibers are oriented along the load direction to resist tensile loads, then the load-bearing capacity is improved, but the fibers become easily torn and the joined state cannot be maintained
Solution Approach 1:
The joint part is designed with asymmetric fiber orientation where reinforcement fibers are arranged perpendicular to the load direction rather than parallel. This asymmetric arrangement prevents fibers from being torn along the load direction while maintaining joint strength through the dovetail shape geometry that redirects stresses.
Solution Approach 2:
The dovetail shape incorporates curved surfaces and angled faces that redirect tensile loads into compressive and shear stresses on the joining surfaces. The curved geometry of the dovetail allows stress distribution that prevents concentrated loading on fibers oriented perpendicular to the load direction.
2Strength
If adhesive is used to secure the joined state against tensile load, then the joint strength is improved, but the complexity of adhesive application and pretreatment increases
Solution Approach 1:
The invention extracts and eliminates the adhesive component from the joining system. Instead of using adhesive to bond the joint parts, the design relies solely on the mechanical interlocking of the dovetail shape, where the projecting part fits into the recessed part with complementary geometries that provide inherent resistance to tensile loads.
Solution Approach 2:
The dovetail-shaped joint parts are designed to self-lock and self-support under load without requiring external adhesive application. The geometric configuration of the projecting and recessed parts creates automatic mechanical engagement that maintains the joined state through its own structure rather than requiring additional bonding materials or processes.
3Device complexity
If dovetail shape is used for physical engagement without adhesive, then the complexity of adhesive handling is reduced, but the ability to resist tensile load decreases when fiber direction aligns with load direction
Solution Approach 1:
The dovetail shape employs asymmetric fiber orientation with reinforcement fibers arranged perpendicular to the load direction. This asymmetric arrangement, combined with the dovetail geometry, creates a configuration where fibers are not subjected to tensile stresses along their length, eliminating the weakness that would otherwise exist in adhesiveless joints.
Solution Approach 2:
The invention shifts the load resistance mechanism from relying on fiber-tensile-strength alignment to utilizing fiber-compression-and-shear strength through the dovetail geometry. By changing the dimensional arrangement of fibers (orienting them perpendicular rather than parallel to load) and using the angled surfaces of the dovetail to redirect forces, the joint achieves tensile load resistance without adhesive.
Data Source
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AI summary
A joint member of a composite including reinforcement fibers and resin and to be joined to a joining part according to an aspect includes: a main body part; and a joint part connecting with the main body part and to be joined to the joining part. The joint part includes a bulging part bulging toward the joining part in an opposed direction in which the joint part is opposed to the joining part, and has an orientation pattern having anisotropy such that fiber directions of the reinforcement fibers included in the joint part include a fiber direction different from a load direction of a load applied to a joined portion of the joint part and the joining part.