Effect of resin pocket area on the mechanical strength and crack propagation of tapered sandwich composites

Sandwich composites have been widely used in large parts of wind turbine blades, as they have high bending stiffness to weight ratio as well as bending strength to weight ratio. Despite many structural advantages, there are some noticeable weaknesses in the manufacturing of sandwich structures. For example, during production of turbine blades using vacuum infusion process (VIP) method, structural defects such as resin pocket area are inevitably created between the composite's face and core. In this paper, four-point bending tests are performed on tapered sandwich composites in order to examine the effect of resin pocket area on the mechanical strength. The results show that the defect area can arrest the crack, therefore, the crack moves in the opposite direction at the interface of face and core. Also this area does not have important influence on the flexural strength of the sandwich composite tapered specimen. Finally, a finite element model is introduced for simulation purposes which these results have good agreements with experimental results.