Thermoplastic Composite Fastener Joining Without Fiber Drilling
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Solution Overview
Problem
Current methods for joining thermoplastic fiber composite components in aircraft construction, such as drilling and self-piercing rivets, face structural and manufacturing disadvantages, including fiber cuttings, delamination, and low mechanical behavior, which necessitate improved assembly efficiency and joint stability.
Innovation Solution
A method involving heating the thermoplastic fiber composite component to soften it, allowing a fastener with a thread to be inserted without drilling holes, which moves the fibers aside, providing increased strength and continuity, and can be applied to components made of thermoplastic materials reinforced with short fibers and nanoparticles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If drilling holes is used to insert fasteners, then assembly is possible, but fibers are cut and delamination risk increases
Solution Approach 1:
The patent changes the physical state of the thermoplastic composite material by heating it to above its melting point, transforming it from a solid rigid state to a softened viscous state. This parameter change allows the fastener to be inserted by displacement rather than cutting, maintaining fiber continuity and eliminating delamination risks associated with drilling.
Solution Approach 2:
The patent replaces the mechanical cutting action of drilling with a thermal-softening process followed by mechanical displacement. Instead of using a drill bit to cut through fibers, the softened material allows the fastener to push aside and displace the thermoplastic matrix and fibers without cutting them, substituting a destructive mechanical process with a non-destructive thermal-softening approach.
2Productivity
If self-piercing rivets are used, then assembly is possible, but crack formation risk increases and fatigue behavior deteriorates
Solution Approach 1:
The patent applies thermal softening to reduce the mechanical resistance of the thermoplastic composite material during fastener insertion. By heating the material above its melting point, the insertion process becomes less aggressive, avoiding the high-stress conditions that cause crack formation and fatigue degradation in self-piercing rivet methods.
Solution Approach 2:
The patent introduces thermal energy as an intermediary that facilitates the fastener insertion process. The heat acts as a mediator between the fastener and the composite material, softening the material to enable insertion without the aggressive mechanical action that causes cracking and fatigue issues in traditional self-piercing methods.
3Strength
If thermoplastic welding is used to join components, then connection is achieved, but mechanical behavior is low due to lack of fiber connection
Solution Approach 1:
The patent uses the softened thermoplastic material itself as an intermediary that fills the space around the fastener and creates a mechanical interlock. The displaced but continuous fibers and softened matrix work together to transfer loads effectively, providing both connection strength and fiber continuity that pure welding methods lack.
Solution Approach 2:
The patent creates a segmented structure where the fastener thread engages with the softened thermoplastic material in discrete regions along its length. This segmentation allows the fastener to create multiple anchor points within the material, distributing stresses and maintaining fiber continuity while achieving strong mechanical connection.
4Strength
If high pressure and high temperature are applied over complete joining area for thermoplastic welding, then joining is achieved, but manufacturing complexity and equipment requirements increase
Solution Approach 1:
The patent applies heat and pressure locally only at the fastener insertion point rather than distributing them over the entire joining area. This localized approach softens the material precisely where needed for fastener insertion, eliminating the need for complex equipment that would be required to apply uniform high pressure and temperature across large surfaces.
Solution Approach 2:
The patent applies heat to soften the thermoplastic material before fastener insertion, preparing the material in advance to facilitate easy insertion. This preliminary thermal softening action simplifies the overall process by eliminating the need for simultaneous high pressure and temperature application during the joining operation itself.
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 enhances joint strength by maintaining continuous fibers and reduces manufacturing complexities, offering improved mechanical behavior and assembly efficiency compared to traditional methods.
Implementation Method 1
heating at least the component which is a thermoplastic fiber composite material while a fastener is screwed into the component
Data Source
AI summary
A method for joining together different components or different sections of a single component, wherein at least one of the components is a thermoplastic fiber composite component, by using a threaded fastener. Heat is used for softening the thermoplastic fiber composite component to be joined together with the threaded fastener. A joined-together fiber composite component of a vehicle, aircraft or spacecraft, can be obtained by the disclosed method.