Strain-controlling mechanical behavior in noncrystalline materials: II: Fracture behavior

A new critical strain criterion controlling the onset of plastic deformation presented in a companion paper (part I) is extended to elaborate peculiar fracture behavior in noncrystalline metallic solids and carbon fiber-reinforced plastic composites. The strain criterion enables one to account for a reason why shear band-induced brittle fracture behavior in Zr-base metallic glasses can more readily proceed in uniform tension than in notched and precracked specimens where the local stress and strain is localized. It is suggested that in noncrystalline alloys environmental effects cause a transition from strain-controlled to stress-controlled fracture particularly under cyclic loading. The strengthening of amorphous polymers by carbon fibers results in strain-controlled brittle fracture, which strongly depends on the strain rate and temperature due to the viscoelastic behavior of matrix amorphous polymers.