The incremental moduli, DELTA G(t), for a concentrated polyisobutylene solution and for a PMMA glass have been determined from step strain experiments in which a small deformation was superimposed on a large deformation gamma //1. DELTA G(t) was found to decrease with increasing gamma //1 and to decrease with time, t//e, after the imposition of the large deformation. In addition, the 'apparent relaxation spectrum' associated with DELTA G(t) narrows and shifts to shorter times when compared to the spectrum associated with the linear viscoelastic modulus, G(t). The results for the PIB solution agree well with the BKZ elastic fluid theory. The BKZ constitutive theory over-predicts the amount of softening observed for the PMMA glass.
|Pages||1. 1-1. 4|
|State||Published - 1985|