Wire Reinforced Plastic Composite Pipe Mechanical Properties

Plastic pipe reinforced by helically cross-winding steel wire (PSP) is a new type of plastic-matrix steel composite pipe, which combines thermoplastic polythene (PE) on the inside and outside of the pipe wall with steel wire mesh skeleton sandwiched in the middle. The mesh skeleton is formed by crossly winding high strength steel wire and tightly integrated with PE by high performance cohesive resin. Owing to the unique structure, PSP not only integrates the advantages of plastic and metal, but also overcomes drawbacks of steel pipe lined with plastic, such as delaminating easily under long-time alternating stress. With the excellent performance of PSP, there has been a growing interest in using it.However, up to now, investigation about PSP is only about its manufacture, fitting and application, at the same time, its mechanical properties have not been reported in literatures. Accordingly, deep study about PSP is necessary and its mechanical response is firstly systematically investigated in this paper. The main research results are as follows:(1)Based on strength equivalent method, short-time burst pressure formula of PSP was deduced. And experimental investigation was also done on 20 different specifications of PSP at normal temperature. The experimental results show that, calculated results are close to experimental data, their relative error is within -11.9%~ 7.4%, and the formula can be used for predicting the short-time burst pressure well.(2)Strain, peel strength, critical buckling pressure and failure mode under various temperatures of PSP were investigated using experiments. As shown in the experimental results, its short-time burst pressure at room temperature is increased by 129%, ring stiffness by 19%, and critical buckling pressure by 57% in comparison with PE pipe. Ductile burst and excessive deformation are the failure modes of the PSP, and their transition temperature is about 45℃. The creep curve of PSP includes two phases, which are the deceleration phase and constant acceleration phase. Moreover, radial expansion rate of the PSP due to internal pressure only exerting inthe radial direction is much larger than that of enclosed PSP. Besides, average peel strength of PSP is 30.53N/mm, and broken types of its interface are mainly mixture damage.(3)Based on long-time hydraulic test, load-carrying ability and service life of PSP are analyzed and predicted by using Standard Regression Method. Forecasting results show that the service life of PSP is longer than 50 years when temperature is 20°C and internal pressure is 1.6 MPa. Furthermore, within trial stretch, regression curve of lower estimating limit of long-term hydraulic pressure does not have brittle failure stage, which indicates that the PSP won't emerge rapid crack propagation.(4)Based on two types of finite-element model, solutions for strains and deformations of PSP under internal pressure and axial force were developed by assuming PSP to be consisted of three continuous layers, i.e., inner layer, composite layer and outer layer. Good agreement between FEM numerical solutions and experimental data shows that the present models can well predict the strains and deformations of PSP, and the finite-element models established in this paper are appropriate.