Reliability assessment of multilayer pipes from polymer materials

Reliability is an important problem when it comes to products made from polymer materials, as polymer materials are characterized by a significant spread of deformation and strength at the manufacturing stage, as well as the strength decrease polymers over time. In addition, products made of polymer materials lose their strength properties, when temperature is increased dramatically. The paper uses the method assessing the probability of failure taking into account these features of polymer materials in relation to single-layer and multi-layer pipes. We collect the initial information in the form of statistical data about deformation strength and limiting properties of polymer materials in the laboratory using standard test methods. Materials specimens were tested immediately after their production, as well as after their exposure for two years in different climatic zones in the open space. Further, this information is used to estimate the parameters of the stress-strain state (SSS) and the quantitative values of the fracture criteria. Since the experimental data have some variation, the parameters of the SSS product and the criteria of destruction are also probable. The proposed and implemented concept of determining the reliability of polymer materials allows obtaining the product reliability estimates when the external load parameters are also random and have a known scattering. Moreover, by taking into account the degradation of polymer matrices over time (aging), we can assess the reliability of structures over time, i.e. their resource.