Experimental investigation of load carrying mechanisms and failure phenomena in the transition zone of locally metal reinforced joining areas

In modern lightweight structures the use of fasteners is preferred to other joining techniques due to the simple disassembly. Because of the low bearing strength of carbon fibre reinforced plastics often a local increase of the thickness is necessary, what is accompanied by eccentricities. A different approach is the local metal hybridisation, where CFRP layers are substituted locally by metal sheets of the same thickness. The local replacement leads to a transition zone between the hybrid region and the pure CFRP region. The present work deals with an experimental investigation of different transition zone patterns and especially the damage behaviour of CFRP-steel hybrid specimens in static tension and bending tests. Digital image correlation is used to measure the strain state during the testing. It is revealed that a staggered pattern with centre endings leads to a high load carrying capacity and a robust transition zone.