Reversible connections for CFK and metal substrates

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The idea and goal of this work is to investigate different reversible techniques to joint CFK and metal substrates in order to detach and recycle them separately at the end of their lifespan. The work will explore:Epoxy adhesives with embedded iron particles for fast debonding via electromagnetic induction heatingNon-reactive high strength hotmelts adhesivesElastically deforming connectors for reversible joining inspired by the press-fit technologyUltrasonic rivet-welding using thermoplastic pins Since boundary conditions for joints differ according to the application, we want to investigate different joining techniques regarding their suitability for material reduction and especially for debonding and recycling after the product’s end-of-life to generate knowledge in the form of a modular design system.Accordingly, we propose the closer investigation of the following concepts:First laboratory tryouts showed that it is possible to break an epoxy adhesive bond between aluminum and CFK substrates via electromagnetic induction if fine iron particles are mixed into the adhesive beforehand. Within seconds, the iron particles heat up and the adhesive degrades so that the substrates can easily be debonded. Advantage is that the type of bonding and the adhesive do not need to be changed. During a project, the ideal type (powder/chips/mesh), size and amount of the metallic particles and the required duration and magnitude of the energy input for adhesive degradation can be explored. Moreover, it needs to be proven that the added particles do not alter the properties of the bond significantly.As another option for detachable adhesives, we suggest investigating the use of high-strength non-reactive hotmelts and thermoplastic adhesives, which could replace epoxy adhesives in specific applications. An increase in temperature (e.g., via infrared heating, induction, or convection) acts as trigger for the debonding. The challenge here is to find and test adhesives suitable for aluminum/titanium and CFK substrates possessing the desired mechanical and thermal properties.Rivets deform plastically during the joining process and join the substrates irreversibly. In contrast, press-fit connectors for PCB-boards deform elastically during insertion and can therefore be easily removed by pressing the pins in the reverse direction. This concept can be transferred to the connection of metal-CFK substrates. Suitable pin geometries can be proposed, designed manufactured using additive manufacturing and tested.Ultrasonic welding machines can be used for joining plastic and metallic substrates via ultrasonic riveting. Usually, a thermoplastic pin sticking up from the lower plastic substrate through a drilled hole in the metal substrate is deformed in a timespan of a few seconds. Here, we suggest altering this technique using a thermoplastic pin protruding both substrates. By locally heating up the connection, the substrates can be detached at the product’s end-of-life.

Project Idea Metadata

• Project Idea Name: Reversible connections for CFK and metal substrates
• Date: 10/13/2022 7:00:50 AM
• Administrators:

Project Idea Description

Since boundary conditions for joints differ according to the application, we want to investigate different joining techniques regarding their suitability for material reduction and especially for debonding and recycling after the product’s end-of-life to generate knowledge in the form of a modular design system.

Accordingly, we propose the closer investigation of the following concepts:

• First laboratory tryouts showed that it is possible to break an epoxy adhesive bond between aluminum and CFK substrates via electromagnetic induction if fine iron particles are mixed into the adhesive beforehand. Within seconds, the iron particles heat up and the adhesive degrades so that the substrates can easily be debonded. Advantage is that the type of bonding and the adhesive do not need to be changed. During a project, the ideal type (powder/chips/mesh), size and amount of the metallic particles and the required duration and magnitude of the energy input for adhesive degradation can be explored. Moreover, it needs to be proven that the added particles do not alter the properties of the bond significantly.

• As another option for detachable adhesives, we suggest investigating the use of high-strength non-reactive hotmelts and thermoplastic adhesives, which could replace epoxy adhesives in specific applications. An increase in temperature (e.g., via infrared heating, induction, or convection) acts as trigger for the debonding. The challenge here is to find and test adhesives suitable for aluminum/titanium and CFK substrates possessing the desired mechanical and thermal properties.

• Rivets deform plastically during the joining process and join the substrates irreversibly. In contrast, press-fit connectors for PCB-boards deform elastically during insertion and can therefore be easily removed by pressing the pins in the reverse direction. This concept can be transferred to the connection of metal-CFK substrates. Suitable pin geometries can be proposed, designed manufactured using additive manufacturing and tested.

• Ultrasonic welding machines can be used for joining plastic and metallic substrates via ultrasonic riveting. Usually, a thermoplastic pin sticking up from the lower plastic substrate through a drilled hole in the metal substrate is deformed in a timespan of a few seconds. Here, we suggest altering this technique using a thermoplastic pin protruding both substrates. By locally heating up the connection, the substrates can be detached at the product’s end-of-life.

The idea and goal of this work is to investigate different reversible techniques to joint CFK and metal substrates in order to detach and recycle them separately at the end of their lifespan. The work will explore:

• Epoxy adhesives with embedded iron particles for fast debonding via electromagnetic induction heating
• Non-reactive high strength hotmelts adhesives
• Elastically deforming connectors for reversible joining inspired by the press-fit technology
• Ultrasonic rivet-welding using thermoplastic pins