Composite tubes subjected to four point bending
Leong, Peng Chuen
Date of Issue2016-05-30
School of Mechanical and Aerospace Engineering
The objective of this study is to identify the how pure bending will affect different materials in the view of assessing the spoolability of these materials. Experiments using four point bending were conducted on multilayered com posite tubular pipes. The multilayered pipes have an external hard layer with a softer inner layer made of high density polyethylene (HDPE) thermoplastic. The external hard layer is made from either polyvinyl chloride (PVC) and glass/epoxy. The interface conditions between the hard and soft layers are either bonded or unbonded. From the experimental results, the deflection and loading versus deflections and loading versus strains graphs show glass/epoxy has a much higher stiffness and larger deflections as compared to PVC. The experimental results also indicated that bonded and unbonded soft layer of HDPE does not affect the stiffness significantly. The minimum spool radius for PVC is 2.5 m while adding a soft layer of H D P E reduces it to 2.08 m for both bonded or unbonded cases. The corresponding increase in moment is 13.65%. For glass/epoxy fibre, the spool radius is about 2.08 m with or without the HDPE layer. There was also a large increase in the loading moment between using glass/epoxy and PVC pipes, a massive 627%. It is conclusive that spoolability performance o f glass/epoxy is much lesser than that o f PVC. While adding a soft inner layer for PVC leads to some increase in spoolability, it does not have any significant impact for the harder pipes such as glass/epoxy. The study also consider the differences between measurements taken on loading movements from the bottom rollers or the top rollers. The results corroborated that the displacement from bottom rollers are more coherent and accurate to the actual displacements. Hence, measurements from loading movements of the bottom rollers should be used in 4 point bending experiments.