Effect of hydrostatic pressure on the elastic work factor, ηel and fracture toughness determination of unidirectional composites using ηel

Previously, fracture toughness of graphite/epoxy composites in the hydrostatic pressure environment was determined using the compliance method. However, it requires four to five test specimens of different crack lengths in order to determine fracture toughness. In this work, the elastic work factor approach was applied to determine fracture toughness of unidirectional (0°) thick graphite/epoxy composites from a single fracture test in the hydrostatic pressure environment. First, the effect of hydrostatic pressure on the elastic work factor was studied. Second, the fracture toughness determined using the elastic work factor approach was compared with that determined from the compliance method at each hydrostatic pressure level. The results showed that the elastic work factor was not affected by hydrostatic pressure, and it decreased linearly with delamination length. The results also showed that the values of fracture toughness determined from both methods were comparable to each other at each hydrostatic pressure.