André Chrysochoos

Influence of Relative Humidity on the Thermomechanical Behavior of PA6.6

An experimental protocol was developed to achieve complete energy balances associated with low cycle fatigue (LCF) of a polyamide 6.6 matrix (PA6.6). The protocol involves quantitative infrared techniques (IRT), and digital speckle image correlation (DIC). IRT data were used with a local heat diffusion equation to estimate strain-induced heat sources, namely dissipation and coupling sources, while DIC enabled strain and stress assessments. Both techniques were then successfully combined to quantify deformation, dissipated and stored energies and then to estimate the Taylor-Quinney ratio that is widely used in plasticity.

Thermomechanical Analysis of the Yield Behaviour of a Semicristalline Polymer

The cold drawing of semi crystalline polymer has been observed in the early 1930s by Carothers and Hill [1]. Ever since, various attempts were made to explain this phenomenon in terms of crystallinity modification. This behaviour, usually related to a rearrangement of the crystallites, depends on the nature of the stretched materials. In some materials, during necking, part of chains in crystalline blocks are unfolded and transfer into amorphous phase with more or less orientation (see Peterlin and Olf [2], Gent et al. [3]). In other polymers, Strauch and Schara [4] exhibit realignment of crystallite. Other authors, Waddon and J., Karttunen [5], emphasize solid-solid phase transition. Nevertheless, everyone agree that a local rise of temperature occurs in the neck shoulders.