The adhesive bond is not the weakest link in current carbon fiber reinforced plastic stiffener to skin structures

A common design feature in aircraft to strengthen skin sections is adhesively bonding stiffeners to them. This has been successfully applied in metal aircraft for years. Those adhesive bonds are usually backed up by rivets, because we are not totally confident about adhesives. So it might be a surprise to learn, that while testing stiffeners made of carbon fiber reinforced plastics, Dr. Sofia Teixeira de Freitas discovered that the adhesive bonds were not the weakest link.Sofia Dr. Teixeira de Freitas is an assistant professor in the structural integrity and composites group at the Faculty of Aerospace Engineering of the Delft University of Technology. Her research is mainly on the structural performance of adhesively bonded structures. And she has discovered a flaw in the current method for designing carbon fiber reinforced plastic joints for aircraft structures.Figure 1: Pull off test setup.Figure 2: The different parts of the pull off test setup. A skin made of glare was used.Figure 3: The tests were carried out with three different spans (L): 100, 200 and 300 mm.Figure 4: Pull off test in process.