β Scribed by V. E. Malpass
No coin nor oath required. For personal study only.
The applicability of time-temperature superposition to tensile stress relaxation of ABS plastics has been verified a t strains from 0.5 to 5% for temperatures in the range of l&50Β°C. Master curves have been compiled to predict the long-term stress relaxation at 23Β°C. and a stress-strain-reduced time surface has been constructed. A comparison of relaxation times and activation energies has confirmed that a strain increase facilitates stress relaxation up to yield. Thedecay of relaxation modulus at linear viscoelastic strains was shown to be equivalent to that of tensile creep modulus. By normalizing the master curves to originate at yield stress and then converting them into multiaxial form the strain which gives the best data fit with long-term hydrostatic pipe-burst strength was shown to be at yield or beyond. The ABS yield-strain master curves at 23Β°C. were shown to match satisfactorily the long-term pipe-rupture data. Activation energies for ABS relaxation have been compared below and above the rigidmatrix T,, to assess the degree of stiffening of the polymer in the solid state.
π SIMILAR VOLUMES
After a brief introduction, where the question of durability related to composite materials is raised concerning the type of applications and the constituents of the composite material, some considerations are given about the interaction between physical and chemical ageing and its eect on the long-