Journal of Reinforced Plastics and Composites

Sandwich composite materials are widely used within the marine industry, particularly as hull panels. Water impact loads, known as slamming, can be very significant for these structures, particularly for high-speed craft. The transient nature of slamming loads means that the loads are applied very quickly, which can cause stress and strain rates that are high enough to affect the resulting strength of the core material, particularly for polymeric foams. The aim of this paper is to characterise the shear strength of cores at slamming relevant loading rates. Two testing approaches are used: a custom servo-hydraulic beam testing system and a drop-weight impact testing machine. Core materials studied included aramid honeycomb, cross-linked and linear polyvinyl chloride, polyethylene terephthalate and styrene acrylonitrile foams, representing a range of different levels of ductility and maximum elongation. For the moderate and high elongation core materials, there were significant increases in shear strength for dynamic loads; however, the strength of most of the materials does not appear to be sensitive to the exact loading rate.

The stress–strain response of an offshore pipe riser subjected to combined internal pressure, tension and bending is studied. Finite element analysis was used to study three conditions of pipe riser – uncorroded, corroded and corroded and repaired with designated laminate orientation of carbon/epoxy or E-glass/epoxy fibre-reinforced composite. The behaviour of the pipe riser (grade API 5L X60 steel) was studied using Ramberg–Osgood model. Two composites laminate systems, a pre-cured prepreg (grade AS4 3501-6 carbon/epoxy) and a wet-layup filament-wounded composite (grade Gevetex LY556/HT917/DY063 E-glass/epoxy), were characterised. Design conditions were determined via a limit analysis known as the double-elastic slope method. The results showed that under combined hoop, tensile and bending loads, the riser tends to approach failure at a much lower strain compared with each of these loads being applied individually. The limiting design factor of the composite repair system was due to excessive tensile strain experienced in a bent riser while the compressive stress caused by reversing the bending load occurred well within the linear-elastic region. With respect to the types of composite repair system, carbon fibre displayed a much better strength rehabilitation over glass fibre. In the aspect of laminate orientation, off-axis plies [90°/ ± 30°]_s and [90°/ ± 45°/0°]_s laminates were found capable of restoring the strength of the corroded riser and provide superior reinforcement in both hoop and axial directions.

One of the typical failure modes of composite repairs in oil and gas pipelines is the formation of a blister underneath the repair. Exceeding the critical pressure, and therefore the critical energy release rate (G_C) for crack propagation, will result in failure of the repair. Knowing the magnitude of the energy release rate (G) is therefore key to understanding the interfacial debonding between a steel pipe and a composite repair. This paper describes two approaches for calculating the value of G for crack advance: (a) a purely analytical evaluation and (b) finite element analysis computation using the pressure–volume method (PVM). The design guidance by ASME and ISO standards for correct dimensioning is also presented, incorporating the most recent changes, which are derived from the work presented here.

This article is concerned with the numerical modelling and analysis of the mechanical behaviour of composite pipes used for offshore oil and gas applications. Specifically, the bending of the reinforced thermoplastic pipes during the reeling process of reel-lay installation is modelled using non-linear finite-element procedures. In particular, the possible buckling of the reeled composite pipes has been investigated. Composite pipes reinforced with one angle-ply and two angle-ply layers are considered and the effects of different diameter-to-thickness ratios and different angle-ply combinations on the mechanical behaviour of these pipes have been studied.

The post-fire integrity of pultruded phenolic/glass and polyester/glass floor gratings, of the type used offshore and elsewhere, was investigated. The aim was to determine whether glass/phenolic gratings may be safely walked on, post-fire, by offshore workers and fire-fighting teams. The load to be resisted was identified as equivalent to a running person carrying a load, the combined mass being 150 kg. The maximum resulting dynamic strains were determined by strain gauges on the undersides of the individual beam elements of gratings. This enabled target values of post-fire bending resistance to be identified. Individual beam elements from the gratings were exposed to heat fluxes of 12.5, 37.5 and 100 kW/m² using a propane burner, for periods up to 16 min, after which the residual strength was measured. Phenolic gratings showed longer ignition times, with lower flame and smoke emission, as well as greater post-fire strength compared to polyester ones. At the lowest flux, 12.5 kW/m², all gratings remained serviceable beyond 16 min. At higher heat fluxes, the phenolic gratings retained some post-fire strength, assisted by the formation of a carbonaceous char binding the fibres. However, this was somewhat below the target level. A study of the effect of testing speed indicated that fire-exposed gratings are not especially strain-rate sensitive.

Grouted sleeves are one of the accepted techniques used for the repair of corroded pipelines. The sleeves are attached over the region of pipe that requires repair, creating an annulus that is then filled with grout material. In this study, the repair system consists of a composite sleeve with polymeric grout. A finite element (FE) study is carried out to predict the effects of selected properties of the composite sleeve and grout on the pipe integrity, subjected to internal fluid pressure. The primary purpose is to identify the main effects and interactions between different material properties, which are useful to aid design decisions for such repairs. While structural reinforcement is provided by the sleeve, the grout plays an important role in transferring hoop pressure in the pipe to the sleeve. Since experimental observations indicate the development of cracks in the grout solely under curing conditions, it is imperative to investigate the effects of such defects. Several different repair conditions that have potential to critically influence the integrity of a repaired pipe are investigated.

A new glass/epoxy prepreg system has been developed as a solution to a long-standing challenge of corrosion and other damage, such as gouging and denting, sustained by piping, pipelines, and risers. The system has been designed to be applicable in the majority of operational conditions encountered in the oil and gas sector, encompassing onshore as well as offshore environments. This paper discusses the comprehensive qualification process undertaken to enable the repair of wall-thinning defects (Type A) and through-wall defects (Type B). The results show that the composite system meets the requirements of ISO/TS 24817 and so also concurrently complies with ASME PCC-2.

Bonded patch repairs are an efficient repair method for corroded or cracked metal structures, if welding is inconvenient. Avoiding the fire hazard of welding is a major reason for using patch repairs, but it can also be reduced distortions of the metal parts, protecting heat sensitive materials or equipment near the repair such as cables and so on. The lack of guidelines for performing such repairs has been a major hindrance for using this technology. A new recommended practice ‘Design, Fabrication, Operation and Qualification of Bonded Repair of Steel Structures’ has been published addressing: when a repair can be applied, which failure mechanisms need to be addressed, which material properties are needed, fabrication-related issues and in-service inspection. This paper will give a brief introduction to the document and its application areas.

This paper presents work conducted to develop numerical tool for heat transfer analysis and cure modelling for the accelerated curing of a composite pipeline repair system. Experimental work was conducted to measure the cure kinetics of the composite material. The measurements were fitted into a cure kinetic model which was subsequently implemented into a FE package through a user subroutine. Applications of the numerical tool to the design and analysis of heating configuration for curing the composite repair are also presented.