Mode II fracture energy of laminated composites enhanced with micro-cork particles

One of the most crucial issues in using composite materials is the delamination phenomenon since it causes a drastic reduction in stiffness and strength of laminates. In this regard, this study is conducted to investigate the effects of micro-cork particles on the characteristics of the R-curve of end-notch-flexure (ENF) specimens made of E-glass/epoxy plain-woven laminated composites. To pursue this goal, Mode II fracture tests were conducted in compliance with the ASTM D7905 standard on ENF samples enhanced with different amounts of micro-cork particles (1 and 3 wt%). According to the experimental results, micro-cork particles showed remarkable potential in increasing the maximum bearable load of the tested composite specimens. The higher the weight ratio of the cork particles, the more stable crack growth. Furthermore, the presence of cork particles also causes a considerable increase in the initiation and propagation of the delamination toughness. The maximum improvement in the initiation fracture toughness and propagation ones were obtained as 127 and 31%, respectively, using 3 wt% of cork particles. To investigate the damage mechanisms at the delaminated surfaces, macroscale and microscopic images using scanning electron microscopy (SEM) were provided. The microscopic images showed that the cork particles hinder unstable crack growth. Various damage mechanisms such as cohesive fracture, fiber breakage, and shear hackles were observed at the delaminated interface.