Improvements in the transverse properties of composites - Part 1 Fracture surface energy and mechanism of transverse fracture in glass fibre composites

Fracture surface energies of initiation (γ_I^c) for a transverse fracture process in glass-reinforced epoxy composites have been measured and the results calculated by three different treatments and are compared with the average fracture surface energies (γ_F^c) for the complete fracture process. Changes in these two fracture properties are studied as a function of the volume fraction of the fibres, and the relation between the surface energies is established as a factor which determines the nature of the fracture process. When γ_I{sic}-γ_F^c>0 a catastrophic failure is expected, whereas a controlled fracture is observed for γ_I^c-γ_F^c<0.