Abstract

Abstract

Abstract

Today’s merchant and passenger vessels are complex structures that operate in harsh environments with respect to static and cyclic loads and corrosion. Depleting funds for fleet renewal and increasing through-life cost of maintenance and repair are the principal factors that lead to the need to implement new solutions that are easy to apply and low cost. All this added to the growing need for lightening in the transport sector turn the FRP materials into the main candidates as drivers for this change.

This present study within RAMSSES is focused on the compare a damage steel structures to repair composite patches. A representative structural detail of a cruise vessel was selected and designed as a demo case. The best patch solution was selected by FEM calculations, which have been fed from the mechanical test results of the composite material combinations, steel, surface treatments and adhesion joint of the one-shot dissimilar joints without adhesive.

Fatigue tests have been carried out and monitoring by strain gauges and FBGs positioning and distribution in the high stress areas along the demonstrator. Fatigue tests have been carried out in the six demos to compare crack evolution in cracked Patched and Un-Patched demonstrators.

As conclusion after the fatigue tests, composite patch works as crack arrested. Therefore, this behaviour represents an improvement of the 2.6 times of the fatigue life comparing UnPatched and Patched damaged steel.

Abstract

Epoxy adhesives films were doped by spraying an aqueous dispersion of carbon nanotubes. Sensing capability of carbon fiber reinforced composite coupons with bonded patch repairs was evaluated; several single lap shear and Mode-I fracture energy tests were conducted and their electrical responses were characterized. It was observed that electrical resistance increases with mechanical strain due to tunnelling effect on CNT percolating networks and increases of electrical resistance associated to crack propagations could be also detected. Once the smart behaviour if the adhesive joints was identified by means of mechanical tests in normalized adhesive joined specimens, panels (400 x 400mm) with square co-bonded patches, made using the same curing cycle based on the repaired material one, were prepared using CNT doped adhesive films. These panels were mechanical tested to determine the effect of the doping treatment on the mechanical behaviour of the repairs, at the same time that electric measurements were carried out to identified local failures during testing. Obtained results showed that structural film adhesives could be surface doped with CNT providing sensing capabilities to be used in structural health monitoring of adhesive repairs in composite structures.