Development of glass fibre reinforced polyethylene pipes for pressure applications

Abstract

Thermoplastic filament winding with in line melt impregnation has been investigated for the manufacture of continuous glass fibre reinforced thermoplastic pipes. With polyethylene matrixes it was found that the high melt viscosity hindered full melt impregnation and resulted in high pull forces in the case of pipe grade polyethylene. Using a lower viscosity polyethylene it was possible to operate the melt impregnation process, but the product obtained exhibited a high void content. Surprisingly, it was found that filament winding resulted in a considerable decrease in void content, to an acceptable level. It was found possible to wind good quality pipes and achieve high failure pressures that fully reflected the strength of the reinforcement.The non-linear strain response of glass-polyethylene pipes can be modelled using laminate theory modified to take account of the non-linearity of the matrix and the change in fibre angle that occurs as the pipe deforms.

A review of the design and analysis of reinforced thermoplastic pipes for offshore applications

“…It can be seen in the experiment that the orientation of the crack in the outer layer of the RTP is almost parallel to the fibre direction in the reinforced tape, which suggests that fibre breakage is the cause of failure of the entire pipe. The same results are observed in the pressure testing conducted by Gibson et al 61 in which all specimens achieve the full strength of the reinforcements. They also demonstrated a modified laminate theory for analysing the mechanical behaviours of fibre-reinforced PE composites in which the nonlinear mechanical behaviour of the matrix materials are modelled numerically.…”

Numerical analysis of the mechanical behaviour of reinforced thermoplastic pipes under combined external pressure and bending

“…The stress-strain relationship of the liner and the cover, which are made of neat PE, is modelled as follows [17]:…”

“…The mechanical behaviour of PE is shown to be nonlinear and the overall response of fibre-reinforced PE composites to loading could be also nonlinear [17]. Given this, the material nonlinearity has been considered in determining the buckling and predicting failures of the RTP under this loading, i.e.…”

Analysis of the mechanical properties of a reinforced thermoplastic pipe (RTP)

“…The resulting displacements in axial direction and the torsion angle can be measured simultaneously. A specially designed linear variable differential transformer (LVDT) device was used [6] for the hoop displacement and an extra measurement of the axial displacement directly on the pipe. The LLRTP should be free to deform during the pressure experiment, therefore force control was used by continuously driving the resulting axial forces and torsion moments to zero.…”