Study of the mode I delamination mechanisms of carbon-epoxy laminated composites

The combination of excellent mechanical behaviour and lightweight of composite materials has motivated research work towards a better understanding of their behaviour in order to arrive at the optimal efficiency. Despite the tremendous progress made in this field, the complex modes of damage are still difficult to comprehend, particularly the phenomenon of delamination. In order to characterize delamination in mode I, double cantilever beam (DCB) type specimens have been used in this study. These specimens fabricated of carbon-epoxy (C/E) with an area of 20 X 6:5 mm 2 , were machined in three configurations where the artificial defect, made of Teflon, was positioned at the midplane of the DCB specimens, i.e. it was situated between layers at (0/0), (0/90 o ) and (90 o /90 o ). The length of these defects varies from 30 mm to 75 mm. The aim of this work was to study the influence of the position of the crack on the delamination of the laminated composites, with different sequences, and particularly on the value of the tenacity. The application of fracture mechanics allows us: to define and to measure the tenacity; to measure the fracture energy during fracture propagation; and to monitor crack growth using R curves.

Keywords:

• Composite Materials
• Delamination
• Tenacity
• Photomicrography
• Crack Initiation
• Propagation