Thermoplastic composite pipes (TCP) are a form of fibre reinforced thermoplastic pipes that have proven benefits such as being lightweight and non-corrosive. However, during manufacturing, certain defects are induced because of certain parameters which eventually affect TCP performance in-service. Current manufacturing techniques are challenged with on-the-spot detection as the pipe is regularly monitored. When a defect is noticed, the process stops, and action is taken. However, stopping the process is costly; hence it is vital to decrease downtime during manufacturing. Potential solutions are through process optimisation for defect reduction and an in-depth understanding of the effect of parameters that cause defect formation in the pipe. This article provides an overview of manufacturing influence on the end performance. This is intimately linked to the material features, properties, and performance in-service. The material features are the determinants for the manufacturing technique to be used. For TCP, it is a melt fusion bonding process involving heating and consolidation among other factors such as the consolidation speed and pull force. Thermal behaviour is essential at this phase as it determines the curing rate and this study indicates that laser heating is the better heat source in efficiency terms. Defects such as fibre misalignments, voids, and delamination are induced during manufactuirng are explored. The sources of these defects have been discussed herein as well as the secondary defects caused by them with the consideration of residual stress impact. The presence of manufacturing defects has been identified to influence the strength and stiffness, interlaminar shear strength, toughness, and creep performance. In addition the study shows there is a need to explore the state of the art in defect characterization during manufacturing for TCP. The in-situ characterization aims to derive high-quality TCP with reduced defects and need for repairs, and increased production rate in safe and eco-friendly conditions while maintaining the current manufacturing process.Graphical abstract

The paper investigates the mechanical properties of coated polyester fabrics in biaxial monotonic tensile tests. The nonlinear behaviors of the constitutive parameters within the full-stress range were in detail analyzed, and a new constitutive model based on the specific coupling relationships between the uniaxial and biaxial flexibilities was proposed to describe the complex tensile behaviors of coated fabrics under plane stresses. Finally, the accuracy of the nonlinear model in numerical simulations was verified, and special attention was devoted to the finite element (FE) implementation of the model as an ABAQUS user material (UMAT) subroutine. It was found that the constitutive parameters of the material varied noticeably with the stress level and ratio. The stiffnesses in the larger-stress direction are nearly stress-dominated, and the stress ratios exert a more significant effect on Poisson’s ratios than that on stiffnesses in the lower-stress direction. The proposed constitutive model, considering the material nonlinearities, is validated by the good correlations between the numerical and experimental results. Additionally, the FE simulation results using the UMAT are consistent with the experiments which reveals that the constitutive model proposed and the results obtained in this work are reliable.