Recent Developments in Durability Analysis of Composite Systems

H. Dardon, H. Fukuda, K.L. Reifsnider, G. Verchery, H. Dardon, H. Fukuda, K.L. Reifsnider, G. Verchery

• Editore: CRC Press
• Anno: 2022
• ISBN:
  9781000446654
• Edizione: 1
• Argomento: Tecnología e ingeniería
• Categoria: Ingeniería civil

The papers from these proceedings address experimental and analytical methods for the characterization and analysis of modern composite and adhesive systems. They have been produced to provide understanding that can be used to design safe, reliable engineering components.

Influence of environmental conditions (moisture-temperature)

Aging and long term behaviour of composite tubes

P. Davies, R. Baizeau & D. Choqueuse

Marine Materials Laboratory, IFREMER Centre de Brest Plouzané, France

L. Salmon & F. Nagot

EDF, Centre de Recherche des Renardières, Moret-sur-Loing, France

ABSTRACT: This paper will discuss results from studies undertaken by IFREMER and EDF over the last ten years. The aim of these studies has been to examine the aging and long term behaviour of glass fibre reinforced epoxy composite tubes for cooling water system applications. First, aging of resins and composites in water is discussed. Results from tests to establish the kinetics of resin hydrolysis are used in a simple model to predict composite degradation with time, and correlated with results from panels immersed for 8 years at 20, 40 and 60°C. Then results from creep tests on tubes under internal pressure with closed ends, lasting up to 18 months are given. Creep strains are shown to be lower than those measured in similar tubes with free ends reported previously. Damaged and assembled tubes have been tested. Finally current research activities are discussed.

1 INTRODUCTION

Thin wall filament wound glass fibre reinforced composite tubes are being used extensively today, but these structures have been available for over 40 years. Early applications were mostly military, such as missiles and rocket casings (e.g. Kies 1962), but they can now be found in chemical engineering plants (Mallinson 1988), fishing boats (Croquette 1992), offshore platforms (Gibson 1993), and many other industrial cooling systems. In oil and gas production the main use is small diameter low pressure pipe for water flood systems. Williams (1999) reports that Shell now has over 2250 kilometres of FRP (fibre reinforced plastic) piping materials in service round the world. Much of the development work for these applications was performed in the 1960’s and 1970’s (e.g. Bax 1970, Spencer 1978).

The main incentive for using FRP pipe systems to replace steel is their good resistance to corrosion, and failure rates in sea water in service have been shown to be significantly lower for FRP (de Bruijn 1996). It was mainly for this reason that in 1991 EDF (Electricité de France) decided to introduce composite circuits in their new nuclear power station at Civaux near Poitiers. The circuits involved bring river water to cooling and fire systems and the stringent safety requirements for such applications required extensive full scale testing at EDF and the CEA (French Atomic Energy Authority). Several collaborative research projects were also run. The present paper presents an overview of results from one such project, with IFREMER, but results from other studies on glass/epoxy tubes with the Applied Mechanics Laboratory, (LMARC) in Besançon (Maire 1992, LeMoal 1993, Thiebaud 1994, Perreux 1995, Suri 1995), Ecole Centrale in Paris (Bai 1996), and on glass/polyester tubes at ENS Cachan (Ghorbel 1996) are also available.

The collaboration between IFREMER and EDF focused on long term behaviour and aging. At the IFREMER Brest Centre glass/epoxy pipework has been used successfully for nearly 30 years in a sea water distribution system, but for the power station application the safety authorities required guarantees concerning the long term behaviour. A programme of aging and creep tests was therefore initiated and results from the first phase were presented at DURACOSYS in 1995 (Baizeau 1995).

In the first part of the present paper the aging of resin and composite samples will be discussed. In 1995 results from 3 year immersion aging of composites were described. Results after 8 years will now be presented, and the basis for a simple lifetime prediction method based on resin behaviour will be shown.

The second part of the paper concentrates on the behaviour of tubes under internal pressure, including creep behaviour of undamaged and damaged tubes. Tubes assembled by mechanical and adhesive systems have also been tested. Finally current research areas and future requirements are discussed.

2 AGING OF EPOXY RESIN AND GLASS/EPOXY COMPOSITES IN WATER.

The degradation of composites in water may result from many different mechanisms, involving the fibre, fibre-matrix interface and matrix resin. In order to treat aging practically simplifying assumptions are therefore necessary. One approach is to determine, for each mechanism, a characteristic time before which the mechanism can be ignored but beyond which it plays a significant role in the dura...