Experimental Study and Finite Element Analysis of Critical Stresses of Reinforced Thermoplastic Pipes Under Various Loads

Abstract

In this paper, reinforced thermoplastic pipes (RTP) were studied under various loads. A total of five groups of specimens were designed to study the mechanical properties of RTPs under internal pressure, bending, a combination of internal pressure and bending moment, external pressure, and tension. This study obtained the bursting pressure of RTPs under internal pressure, the minimum bending radius under the bending moment, and the failure pressure under external pressure. At the same time, the mechanical properties of RTPs under various loads were analyzed using the finite element analysis. Analytical results agree well with the experimental ones. The finite element model established in this paper can be used for further research on the mechanical properties of RTPs.Introduction. Pipes are widely used in urban and rural water supply, as well as oil and gas transportation industries. In the field of oil and gas pipelines, steel pipes are most widespread due to their high strength and good weldability. However, poor corrosion resistance, high quality defects, and the heavy self-weight of the whole steel pipe have restricted the development of oil and gas pipeline engineering. Although plastic pipes can provide a good corrosion resistance performance, their strength is too low to meet the requirements of oil and gas transportation. Fortunately, composite pipes overcome the shortcomings of steel and plastic ones and combine their advantages, which allows their rapid application in engineering. A reinforced thermoplastic pipe (RTP) is formed with an inner layer (polyethylene, etc.), a composite layer (polyester fiber, aramid fiber, high-strength steel wire), and an outer layer (polyethylene). The pipe structure is shown in Fig. 1. Such pipe exhibits high toughness and strength characteristics and is currently used for water transportation in marine, urban, and rural areas; it will be also promoted for long distance oil and gas pipelines.At present, scholars have been researching the mechanical response and strength of this kind of composite material. Some mechanical data, such as dependences between stresses, strains and displacements for composite pipes with different winding angles and thickness-to-diameter ratios under complex loads have been found [1][2][3][4][5][6][7][8][9][10]. The influence of the winding angle on the pipe critical load was also studied through experiments and finite element analysis [11][12][13]. However, RTPs will face more complex load conditions if they are used in long-distance oil pipelines. It is critical that the pipe can ensure the oil transportation safety. Therefore, more in-depth research on the mechanical properties of RTPs under various loads is necessary to provide a reference for the design of oil and gas pipelines. This paper focuses on the mechanical properties of RTPs reinforced with steel wire under various loads, such as internal pressure, bending, a combination of internal pressure and bending, external pressure, and tension, by experimental study and finite element ana...

Non-uniform crystallinity and temperature distribution during adjacent laser-assisted tape winding process of carbon/PA12 pipes

“…There have been several studies to evaluate the in situ consolidation development during LATP of carbon-reinforced thermoplastics [14,18,[20][21][22][23] and LATW of glass fiber/phenolic resin thermoset [16]. Also, the mechanical performance of the composite pipes was studied for various loading conditions [24][25][26]. The degree of crystallinity (DoC) is another temperature-dependent structural parameter which affects the mechanical performance of the crystalline FRP products [27][28][29][30][31][32].…”

An overview of burst, buckling, durability and corrosion analysis of lightweight FRP composite pipes and their applicability

“…Only very few studies have been reported on thermoplastic matrix composite pipes, despite of their recent and wide industrial applications. A study was carried out on the burst analysis with the application of internal pressure and combination of bending moment for steel/polythene reinforced thermoplastic polymer [105]. The burst failure was observed at the ends of the pipes at 18 MPa.…”

Towards an accurate process design tool for laser-assisted tape winding

“…There have been several studies to evaluate the in-situ consolidation development during LATP of carbon reinforced thermoplastics [52,32,76,80,81,47] and LATW of glass fiber/phenolic resin thermoset [78]. Also, the mechanical performance of the composite pipes was studied for various loading conditions [82,83,84]. The degree of crystallinity (DoC) is another temperature-dependent structural parameter which affects the mechanical performance of the crystalline FRP products [85,86,87,88,89,90].…”