Dominique Choqueuse

Micro-Tomography to Study High-performance Sandwich Structures

Although X-radiography has been widely used in studies of damage in composite materials, micro-tomography has received less attention, due to the high cost and limited availability of equipment. However, micro-tomographic analysis is a powerful tool, allowing 3D images of sections through sandwich materials to be obtained without specimen preparation. Four examples from a recent study are presented here, which show how micro-tomography can provide unique information on the quality of honeycomb sandwich structures, information on damage mechanisms and internal details of through thickness reinforcement in pinned foam cores.

Mechanical behavior of syntactic foams for deep sea thermally insulated pipeline

Ultra Deep offshore oil exploitation (down to 3000 meters depth) presents new challenges to offshore engineering and operating companies. Flow assurance and particularly the selection of insulation materials to be applied to pipe lines are of primary importance, and are the focus of much industry interest for deepwater applications. Polymeric and composite materials, particularly syntactic foams, are now widely used for this application, so the understanding of their behavior under extreme conditions is essential. These materials, applied as a thick coating (up to 10-15 cm), are subjected in service to: - high hydrostatic compression (up to 30 MPa) - severe thermal gradients (from 4°C at the outer surface to 150°C at the inner wall), and to high bending and shear stresses during installation. Damageable behavior of syntactic foam under service conditions has been observed previously [1] and may strongly affect the long term reliability of the system (loss of thermal properties).This study is a part of a larger project aiming to model the in-service behavior of these structures. For this purpose it is important to identify the constituent mechanical properties correctly [2, 3]. A series of tests has been developed to address this point, which includes: - hydrostatic compression - shear loading using a modified Arcan fixture This paper will describe the different test methods and present results obtained for different types of syntactic foams.

Structural mechanical testing of a full-size adhesively bonded motorboat

This paper describes the tests performed on a full-size motorboat to demonstrate the potential for adhesive bonding to replace overlaminated connections. Adhesive bonding resulted in a significant reduction in assembly time for bulkhead connections compared with overlamination. Drop tests and sea trials were performed using specially adapted strain gauge instrumentation. These indicated low adhesive joint strain levels, even for severe test conditions. No damage was observed. The data obtained will be used to improve laboratory test procedures to simulate service loading of boat structures.

Development of a Test to Simulate Wave Impact on Composite Sandwich Marine Structures

Wave impact is a potentially damaging load case not only for fast ships and racing yachts but also for wave energy devices and signal buoys. This chapter describes the development and analysis of a test designed to simulate the response of composite and sandwich marine structures subjected to wave impact. First a brief overview of previous work on impact of composites and sandwich materials is given, and existing tests to study wave slamming are discussed. The development of a medicine ball test is then described, and examples of results from tests on various sandwich panels are given. Finally, the evolution from a qualitative to a quantitative test is described, FE modelling is discussed and examples of results are given.

Failure of polymer matrix composites in marine and off-shore applications

Abstract: Composites are widely used in marine applications and there is considerable experience of their behaviour in service. This chapter first describes the different materials used for marine structures. Then a series of tests which have been developed to simulate the loading of marine structures, both for surface vessels and underwater structures, will be presented, and examples of failures will be described.