Effects of thermal gradient on failure of a thermoplastic composite pipe (TCP) riser leg

Abstract

Thermoplastic composite pipe (TCP), consisting of a fibre-reinforced thermoplastic laminate fully bonded between homogeneous thermoplastic liners, is an ideal candidate to replace traditional steel riser pipes in deepwater where high specific strengths and moduli and corrosion resistance are advantageous. During operation, risers are subjected to combined mechanical and thermal loads. In the present paper, a 3D finite element (FE) model is developed to analyse stress state in a section of TCP under combined pressure, axial tension and thermal gradient, illustrative of a single-leg hybrid riser (SLHR) application. From the obtained stresses, through-thickness failure coefficient is evaluated based on appropriate failure criteria. The effects of increasing the internal-to-external thermal gradient are investigated considering temperature dependent material properties. The influence of varying the thickness of the isotropic liners with respect to the laminate is examined.

Failure analysis of thermoplastic composite pipe (TCP) under combined pressure, tension and thermal gradient for an offshore riser application

“…where ̅ are stiffness constants corresponding to a unidirectional layer orientated at angle φ about the pipe r direction as per Figure 4; αz, αθ, αr and αzθ are the cylindrical coefficients of thermal expansion (we note the orthotropic ply is along z and θ leading to a coupling effect and non-vanishing αzθ); ΔT is the temperature change. The radial temperature distribution for a through-thickness thermal gradient bound by T0 and Ta is obtained by considering steady state conduction and heat flux layer continuity, as outlined in [21]. The strain-displacement relations are [22,23] (…”

“…In the previous paper [21], a 3D FE model for predicting stress state in a section of TCP under combined pressure, tension and thermal gradient was developed in Abaqus/CAE and validated using an analytical solution based on the problem formulation presented in Section 2. The model is used here to study the TCP configuration in Table 1 under different combinations of pressure, tension and thermal gradients.…”

“…APC-2 PEEK composite has a glass transition temperature (Tg) of 143°C and can be used in lightly loaded applications at temperatures as high as 260°C [24]. A comprehensive set of temperaturedependent mechanical and thermal properties compiled from literature and listed in [21] was used to define the materials over the temperature range considered in this study. The FE model is shown in Figure 5.…”

“…In the previous work [21], a 3D FE model was developed to study the effects of through-wall thermal gradient on stress-based failure of TCP under combined pressure and axial tension illustrative of a deepwater riser application. In the present paper, the developed model is used to investigate the effects of varying pressure and thermal gradient combinations on local TCP failure response.…”

Numerical modelling of spoolable thermoplastic composite pipe (TCP) under combined bending and thermal load

“…Predicted burst pressure decreased by 2-3% based on coefficients obtained from 30-day submersions of specimens at 80°C. Hastie et al (2019aHastie et al ( , 2019bHastie et al ( , 2020 performed 3D FEA to investigate the influence of thermal gradient on the failure of carbon/PEEK TCP under combined pressures and tensions illustrative of deepwater riser operation. The effects of increasing operating temperature are less pronounced under high pressure where the laminate experiences greater utilisation.…”