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Research of the load bearing capacity of shape-optimized metal inserts embedded in CFRP under different types of stresses

Mittwoch (05.07.2017)
14:00 - 14:20 Uhr
Bestandteil von:

An efficient implementation of lightweight design is the use of continuous carbon fiber reinforced plastics (CFRP) due to their outstanding specific mechanical properties. Embedded metal elements, so-called inserts, can be used to join attachments to structural CFRP parts. They differ from other mechanical fasteners and have distinctive benefits. In particular, drilling of the components to be joined can be avoided and fiber continuity can be maintained using such elements. Thus, no local bearing stress is anticipated. Previous work [1] dealt with a systematic research of the influence of different types of stresses on the load bearing capacity of welded inserts. This paper aims at the investigation of the performance of shape-optimized inserts under the same types of stresses to compare with the results of the welded inserts serving as a reference. For this, the respective load bearing capacities were evaluated after preinduced damages from impact tests and thermal-cycling. In addition, dynamic high-speed tensile tests (pull-out) were conducted under different loading velocities. It turned out that the load bearing capacities increased up to 100% for very high velocities (15 m/s) in comparison to quasi-static loading conditions (1.5 mm/min) showing an obvious strain rate dependency of the insert/laminate consisting of an epoxy resin. Quasi-static residual strength measurements under tensile loading identified the influence of the respective preinduced damages of the insert. Influence of the thermal loading condition was evaluated by placing the specimens in a climate chamber and exposing it to various numbers of temperature cycles from -40 °C to +80 °C with a duration time of 1.5 hours each. Here, it turned out that already 10 temperature cycles decreased the quasi-static load bearing capacity of both insert variants up to 20%. According to DIN EN 6038 the specimens were loaded with different impact energies and the residual strength were measured carrying out pull-out tests. It could be shown that the damage tolerance is significantly lower for the shape-optimized insert due to failure-critical delamination. The optimized insert also endured lower impact energies and the influence on the performance was higher.

Florentin Pottmeyer
Karlsruher Institut für Technologie (KIT)
Weitere Autoren/Referenten:
  • Markus Muth
    Karlsruher Institut für Technologie KIT
  • Prof. Dr. Kay André Weidenmann
    Karlsruher Institut für Technologie KIT