The issue of impact simulation results from the fact that the impact load is unique and the designed system or element is requested not to fail only once or a small number of loadings. Tests for assessments of the degree of impact protection are expensive and numerous because they require a high probability of impact resistence. In the literature, there are models at the micro level (at fiber level), at the meso level (multi-fiber yarns, several fibers or by evaluating the behavior of the fibers to a monobloc yarn, as is the case with this simulation) and at the macro level (the behavior of element or system is done with some equivalences concerning the material model). This paper presents comparative results of the axis and on the edge of a yarn considered monoblock and isotropic to highlight the differences in the mechanisms of destruction of the yarn and in the evolution of the distribution of equivalent stress, highlighting the differences in the simulation of these two cases explains, at least qualitatively, the differences in the behavior of the panels considered identical.

This paper presents results on tribological characteristics for polymer blends made of polybutylene terephthalate (PBT) and polytetrafluoroethylene (PTFE). This blend is relatively new in research as PBT has restricted processability because of its processing temperature near the degradation one. Tests were done block-on-ring tribotester, in dry regime, the variables being the PTFE concentration (0%, 5%, 10% and 15%wt) and the sliding regime parameters (load: 1 N, 2.5 N and 5 N, the sliding speed: 0.25 m/s, 0.5 m/s and 0.75 m/s, and the sliding distance: 2500 m, 5000 m and 7500 m). Results are encouraging as PBT as neat polymer has very good tribological characteristics in terms of friction coefficient and wear rate. SEM investigation reveals a quite uniform dispersion of PTFE drops in the PBT matrix.