Study on short-term mechanical properties of multi-reinforced steel-plastic composite pipe under internal pressure

A multiple-reinforced steel-plastic composite pipe (MRSPCP) is a new type of composite pipe developed in China recent years. The MRSPCP is composed of high-density polyethylene (HDPE) matrix, steel-wire mesh, and steel strip. It is an improved version of the traditional structural wall pipe, and it is able to carry both external and internal pressures. Nowadays, it has been employed in many projects that require large diameter and high flow media transportation, such as water distribution systems, drainage systems, agricultural irrigation systems. As the MRSPCP is newly developed, its mechanical properties and failure mechanism are not clear, and its design method lacks theoretical basis, so this paper carries out the experimental, theoretical and simulated research to investigate the short-term mechanical properties of the MRSPCP. Firstly, uniaxial tensile tests are carried out to acquire the mechanical properties of the constituents. As the steel wire is curly and it is hard to get the stress-strain relationship directly, an inverse identification method was applied to determine the mechanical parameters of a bilinear model representing the steel-wire mechanical behavior. Moreover, short-term burst tests of the MRSPCP are carried out to assess its mechanical performance and provide data for the verification of the theoretical and simulated research. Secondly, a theoretical model is established to calculate the failure pressure by constructing force equilibrium relationship along the axial and hoop directions of the MRSPCP respectively, based on elastic mechanics. In the end, a finite element model of MRSPCP is established, considering the nonlinear mechanical property of the materials. Both the theoretical and the simulated results agrees well with the burst test result, with the relative error of only −13.18% and −4.41% respectively. As the finite element model not only provides more accurate result, but also it can demonstrate contour plots of different constituents inside the MRSPCP, the model is used to study the effects of the pipe thickness, composite strip winding angle and steel-wire diameter on the mechanical properties of MRSPCP. This study might be a guide for the design and safe application of the MRSPCP and similar composite pipes.