Experimental Studies of Compression and Impact Behaviours of Traditional Versus Alternative Polymer Support Materials for Pipelines

Abstract Non-metallic materials such as polymers and woods are commonly used as pipeline supports to distribute loads and dissipate mechanical vibrations. Neoprene is a synthetic rubber material widely used for these purposes but is softer than other common polymer materials such as Ultra High Molecular Weight Polyethylene (UHMW) or Polytetrafluoroethylene (PTFE). It is also generally less available and more expensive than natural materials like woods. Because there is an apparent lack of data on the compressive and impact resistance behaviors of pipe support materials, dedicated experiments were conducted on Neoprene, UHMW, Polyethylene (PE), PTFE, Polyvinyl Chloride (PVC), Polyurethane (PU), and wood samples in this study. The influences of several factors such as temperature, layering, strain rate, and vibration frequency were evaluated. Understanding the differences in mechanical behaviour of these materials is important for pipeline design and stress calculations/simulations. For compression tests, a 10″ (25.4 cm) diameter conical shaped custom compression platen was designed and analyzed numerically with Finite Element Analysis (FEA) to ensure it met specific weight, maximum deflection, and alignment requirements. These custom platens were fabricated for the experiments from 1018 steel case-hardened for durability and stiffness. For impact experiments, a 12″ (30.5 cm) diameter pipe was set up on a supporting bracket with isolation liners (test materials) sandwiched between the pipe and the support and between the pipe and the bracket. Accelerometer sensors were installed on the pipe and underneath the two support legs of the assembly. Transfer functions on the pipe wall and underneath left and right support legs were measured when impacted using a calibrated force hammer. Compression tests under monotonic loading showed that PTFE was the stiffest material tested at maximum load, approximately 18% stiffer than Neoprene. Layering had an insignificant effect on the final compressive strain values at the maximum compressive load. However, between 10–100 MPa (1.45 ksi – 14.5 ksi) during the compression stroke, the stiffness of the overall sample is ∼10% lower with more than one layer. Impact tests revealed that PVC and Neoprene materials were more effective than PU in dampening the vibration response in the lower frequency range up to 700 Hz and higher frequency vibrations in the range 1000 Hz through 2000 Hz. None of the tested materials were effective in dampening the pipe vibrations excited in the range between 700 Hz and 1000 Hz.