Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Local buckling failure analysis of deep sea CFRP armour unbonded flexible riser
Yijun Shen 1),*Hu Liu 1),2)

1) State Key Laboratory of Marine Resources Utilization in South China Sea, Hainan University, Haikou, China
2) School of Civil and Architectural Engineering, Hainan University, Haikou, China

further elevated specific strength low density, excellent fatigue resistance,and corrosion resistance, and thus replacing traditional steel with carbon
fiber is one of the solutions to solve the excessive weight and corrosionof flexible risers. During installation and operation, the riser may besubjected to axial compression and bending loads, as well as two
potential mechanisms for stable failure of the pipe tensile armor:-Radial buckling, also known as Birdcaging, which is usuallyoccurred under axial compressive load.

ABSTRACTAs the oil and gas industry turns to the deep sea, flexible risers are
becoming more and more widely used. To effectively achieve thelightweight and high strength requirements of ultra deep-water oil andgas development, it is a new trend to replace steel with CFRP. For deepwater flexible riser systems, the riser is bearing axial load, bending, andpressure during installation and operation, which may lead to local
buckling. The carbon fiber reinforced material replaces the steel of tensile
armor with a higher strength-to-weight ratio compared to metal risers, but
its performance in deep water environments is less experienced. Firstly,
this paper mainly describes the buckling behavior of a flexible riser, a 3D
FE model was established by using ABAQUS to study the radial bucklingmechanism. Then, to study the influence of different conditions on thebuckling behavior through numerical simulation. Finally, the results ofthe finite element model are compared with the experimental data toprovide some theoretical experience for the actual design andmanufacture of CFRP in a flexible riser.

KEY WORDS: CFRP; Local buckling; composite risers;
numerical model; tension armor.

Fig. 1 Radial buckling (Bectarte et al, 2004)

INTRODUCTION- Lateral buckling, which is generally formed under cyclic bending
load.

Since the 21st century, resource development has gradually moved
from land to sea. Flexible riser plays a key role in the development of
deep-sea oil and gas resources. The traditional flexible riser is mainly
made of the structure layer of metal materials and the functional layer ofpolymer materials. The structure layer is mainly made of high-strength
steel such as carbon steel, stainless steel, etc. Nowadays, Resource
development moves to the deep sea from the shallows gradually, and theweight of the flexible pipe has increased following the deepened of oil
and gas exploitation, so comes with the broader size of the platform.
Traditional steel is with deficiencies like short service life andcomplicated maintenance in the face of high-temperature corrosion of oil
and gas. To solve these problems, people turn to fiber reinforced
materials, such as Aramid, Glass, and Carbon fiber, to replace the steel inthe structural layer of flexible riser. Fiber reinforced materials showFig. 2 Lateral failure (Secher et al. 2011)116