Connecting elements for composite design
The key challenges for affordable lightweight design based on carbon fiber reinforced plastic materials include the reduction of material costs, design and simulation, recycling, damage detection, and also the technologies employed to make reliable connections to other materials.
The direction-dependent properties of composites ("anisotropy") and the complex interactions between fibers and polymer matrix differ significantly from the mechanisms encountered when using metallic structures. Currently available and recognized connecting technologies include adhesive bonding and the additional securing by means of bolts and rivets.
However, adhesive bonds cannot be quantified to a sufficient extent and vary in their joint strength depending on ambient conditions. Besides, it is very costly to assure their quality. In the case of bolting and riveting, there is no way to avoid local transection of load-bearing fibers.
We at TEUFELBERGER developed T-Igel®, an innovative connection technology, all the way to market readiness. It is superior to the above-mentioned technologies, both technologically and economically:
- The resulting adhesive bond via the RTM epoxy resin in combination with a form fit (between pins and fibers) helps achieve connection strengths of up to 60N/mm2 and high safety factors.
- Structurally quantifiable connection due to known scaling of shear strengths of the individual pins. Virtually independent of ambient conditions. This makes shorter connection lengths in combination with simpler designs possible.
- The fully automated process used to apply the pins works with stainless steels and aluminum. It permits a flexible pin geometry (thickness, length, shape). Hence, this connection can be attuned exactly to the load specification. Also, because of its great ease of integration into the fiber composite, it is considerably less expensive than structural adhesive bonding.
- Predictable and more plastic failure behavior.
T-Igel® was developed by TEUFELBERGER especially for closed end piece cross sections (circles, polygons) and has been patented internationally for integration with braiding and winding processes. Areas of application for this one-of-a-kind connection technology can be found in all segments of lightweight engineering. Depending on the field of use, T-Igel® is designed with internal or external threads, as tab, eye, sheet, fork finger (etc.)
Another development of TEUFELBERGER are grid frame nodes of composite design. In this case, special adhesive-bonded gusset plates or clamped structural collars are used to connect the various CFRP sections. Of course, we at TEUFELBERGER also use adhesive bonding and riveting for specific applications – depending on the needs of our customers!