Synchrotron Laue microdiffraction and Digital Image Correlation measurements were coupled to track the elastic strain field (or stress field) and the total strain field near a general grain boundary in a bent bicrystal. A 316L stainless steel bicrystal was deformed in situ into the elasto-plastic regime with a four-point bending setup. The test was then simulated using finite elements with a crystal plasticity model comprising internal variables (dislocation densities on discrete slip systems). The predictions of the model have been compared with both the total strain field and the elastic strain field obtained experimentally. While activated slip systems and total strains are reasonably well predicted, elastic strains appear overestimated next to the grain boundary. This suggests that conventional crystal plasticity models need improvement to correctly model stresses at grain boundaries.
Polyetherketoneketone (PEKK) is of increasing interest
for the
manufacture of composites in the aeronautical field. It is essential
to evaluate the PEKK absorption of fluids, especially water, with
which it may come into contact during its processing and use. In this
work, we provide for the first time water transport parameters such
as water diffusivity and solubility for PEKK in amorphous and semicrystalline
states using water immersion as well as dynamic vapor sorption (DVS)
experiments. Water diffusion is modeled using Fick’s second
law with variable boundary conditions, taking into account possible
relative humidity variation during the DVS experiments. Based on similar
characterizations of PEEK, we discuss the fact that PEKK absorbs more
water than PEEK in terms of polarity.
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