Mechanical behavior prediction of PPR and HDPE polymers through newly developed nonlinear damage-reliability models

Abstract

Many polymers have been developed through the years to satisfy the continuous demand of industrials and the development of the fields of usage of these materials. Indeed, the High Density Polyethylene (HDPE) and the Poly Propylene (PPR) are famous materials and have diversified utilizations. To predict their mechanical behavior, we leaded burst tests on multilevel groove notched pipes and we compared the general behavior of the internal pressure of burst. We noticed a drastic drop in the burst pressure in function of the life fraction. The HDPE and PPR materials are showing a ductile behavior with two characteristic pressures at the end of the elastic phase and the rupture phase. The HDPE has a stable plastic phase and show a perfect ductile behavior. Meanwhile the PPR have a short plastic phase and show similarities to an old HDPE pipe tendency. It is shown that the PPR has reverse characteristic pressures at the opposite of the HDPE ones. We have noticed that the two materials change the corresponding level of loading to recover the noticed deformation in the plastic phase. The obtained parameters allowed us to establish new concepts of damage modeling through the modification of usual nonlinear models existing in the literature which has been initially proposed for steel materials. The static model of the unified theory which have been developed based on the burst pressure parameters and allowed us to predict the burst pressure damage evolution according to the life fraction, representing the harmfulness of the notch. The static damage evolution is representing the damage corresponding to each notch. Then, we compared the effect of the notch level on PPR and HDPE materials. Finally, we analyzed the noticeable discrepancies between PPR and HDPE and we showed the advantages of such models to make the quick checks easier and reliable by only using static test of burst.