Within Work Package 4, the Composite and Smart Materials Laboratory of the University of Ioannina evaluated the knockdown effect between 3R and conventional (RTM6) composites and the repair efficiency.
In terms of interlaminar shear strength and low velocity impact values, the 3R composites exhibited a very negligible knockdown effect of about 3-4%, proving that the 3R resin had similar mechanical properties to a typical aerospace grade resin (RTM6). The first repairing process was performed at IVW, using a hot-pressing process.
The repair efficiency concerning the ILSS geometry was evaluated at about 72%, while at LVI geometry, the initial values were recovered by 87% in terms of average maximum load and by 105% in terms of the absorbed energy at two energy levels (9 J and 15 J).
All the aforementioned results were confirmed using a variety of non-destructive techniques (IR thermography, phased array ultrasonics, etc.) simultaneously with the mechanical testing. In parallel, AEF is developing a methodology to model 3R composites repaired structure.