Delamination in UD-CFRP steel hybrid laminates - Part 2: Effect of damp-heat aging

Description

Steel/composite-hybrids with varying inter-plies were investigated. A unidirectional carbon fiber reinforced prepreg with a toughened epoxy matrix and a nominal fiber content of 60 v% was applied to a cold-rolled steel sheet. As inter-plies both, polar and non-polar polymers were used. Furthermore, the steel surface was modified, e.g. via phosphatization. After damp-heat aging in climate chambers at 60°C and 85% r.h. the laminates were characterized by monotonous tensile testing. Therefore, a novel fracture mechanics testing methodology was implemented and described in part 1 of this paper series. As specimen the double cantilever beam geometry was used with fluoropolymer insertion layer as crack-starters. Significant deterioration of interlaminar properties of hybrid, hybrid/phosphated and hybrid/polar inter-ply laminates by damp-heat exposure was found. After 2000 hours the hybrid laminates without inter-ply exhibited premature failure without additional mechanical loading. In contrast, the aging performance of the hybrid with phosphated steel surface was significantly better. The initial critical energy release rate of 0.1 kJ/m² was reduced slightly. The best performance was obtained for the hybrid laminates with non-polar inter-plies, which exhibited a factor of more than 5 higher critical energy release rate.

Period	20 Apr 2016
Event title	Euro Hybrid Materials and Structures 2016
Event type	Conference
Location	GermanyShow on map