Correlation between macroscopical viscoelastic behaviour and micromechanisms in strained alpha polyvinylidene fluoride (PVDF)

Links between macroscopical behaviour and micromechanisms of deformation (c onstrained amorphous shearing, crystalline lamellae slip or unfolding, micr o-voiding) are studied in uniaxial tension and creep tests performed on apo lar PVDF at different strain rates (tensile tests), stresses (creep tests) and temperatures. Volume changes are simultaneously measured to take into a ccount cavitation processes. The major influence of amorphous phase shearin g and its competition with cavitation are described for temperatures rangin g from ambient up to 100 degrees C. Concepts of crystallite unfolding are i ntroduced and used to understand particularities of high temperature deform ation. Unfolding processes are suggested to be responsible for the differen t long-term behaviour (creep kinetics and fracture). (C) 2000 Elsevier Scie nce S.A. All rights reserved.