Plasticity‐controlled failure of sintered and molded polyamide 12: Influence of temperature and water absorption

Abstract

The influence of stress, temperature, and relative humidity on plasticity-controlled failure of molded and laser-sintered polyamide 12 (PA12) has been investigated. Ree-Eyring's flow theory is employed and modified to take into account the effect of relative humidity on the deformation kinetics. By introducing the concept of critical strain, time to failure in plasticity-controlled regime is predicted starting from the yield kinetics. Creep test is performed to estimate the critical strain and to validate model predictions. The model predictions are in good agreement with the experimental results, showing that the model is a suitable and reliable tool to evaluate mechanical response as function of temperature and relative humidity. We demonstrate that, while, at high applied strain rates, a significant difference is found, the mechanical response under constant strain rate as well as the failure kinetics in plasticity-controlled regime of the sintered PA12 are comparable with those of the molded material.

Laser-based additively manufactured polymers: a review on processes and mechanical models

“…Beyond a certain number of layers, which is usually exceeded in the production of the final component, the transition from a mostly viscous liquid to a viscoelastic solid is initiated well before the beginning of the controlled cooling stage [46]. The effect of the crystalline phase of laser-sintered parts has been related to the temperature-and rate-dependent behaviour of polymeric materials [127], and the effect of inhomogeneous crystallisation was also linked to warping of the printed parts [91]. In general, the behaviour of semicrystalline polymers is complex because of different contributions during the deformation of the material, deeply affected by rate and temperature [176].…”

“…Paolucci et al [127] have recently focused on the ductile failure of PA12 laser-sintered specimens, using a modified form of Ree-Eyring activated flow theory [129,130] to describe the rate-and temperature-dependent yield stress, which is given as…”

“…where _ e is the strain rate, V Ã is the activation volume, _ e 0 is the rate factor and the subscripts 1,2 are related to intralamellar and interlamellar deformation, respectively [127]. In Fig.…”

“…. In practice, the effect in terms of mechanical properties is analogous to an increase in the ambient temperature [127].…”

Deformation and failure kinetics of polyvinylidene fluoride: Influence of crystallinity

“…In the present investigation, this approach, which was proven successful also for other semi-crystalline polymers, 16,[21][22][23][24][25] is applied on PVDF; in addition, the effects of crystallinity will be incorporated. The procedure followed in the present study is based on the mechanical characterization of PVDF with different thermal histories, complemented by the characterization of the microstructure through X-ray analyses.…”