MARINE AND OFFSHORE COMPOSITES 3 – 4 February 2010, RINA HQ, London PAPERS THE ROYAL INSTITUTION OF NAVAL ARCHITECTS Marine and Offshore Composites CONTENTS APPLICATION OF COMPOSITES IN SHIPS AND OFFSHORE – A REVIEW AND OUTLOOK J Weitzenböck, D McGeorge, D Hill, B Hayman, A Echtermeyer, P Noury, K Brinchmann, G Hersvik, A Fredriksen, D Ohlsson, DNV USE OF CARBON FIBRE IN HIGH SPEED PASSENGER FERRIES M Håkansson, Kockums AB FRP SANDWICH VESSELS FOR THE SWEDISH NAVY (presentation only) A Lonno, FMV, Defense Material Administration, Sweden A TAXONOMY FOR RESIN INFUSION PROCESSES J Summerscales, University of Plymouth TOWARDS RECYCLABLE COMPOSITE CRAFT: FUSION BONDED THERMOPLASTIC COMPOSITE T-JOINTS M Otheguy, G Gibson, Newcastle University B Cripps, BVT Surface Fleet Support EFFECTS OF ZINC-BASED COMPOUND ON DEGRADATION BEHAVIOUR AND SMOKE PRODUCTION OF EPOXY MATRIX A. De Fenzo, C. Formicola, V. Antonucci, M. Zarrelli, M. Giordano, IMCB-Institute of Composite Materials and Biomedical CNR- National Research Council, Italy DEVELOPMENT OF DESIGN EQUATIONS FOR STEEL SANDWICH PANEL CONSTRUCTION SJ Kennedy, MA Brooking, Intelligent Engineering Y.Heo, MS Kim, DSME H Ocakli, Lloyd’s Register IN-SERVICE COMPOSITE INTEGRITY MONITORING SYSTEM (I - CIMS) B Walker, P Faulkner, P Guy, J Tracey, Tangent Technologies Ltd S Smith, C Gowrely, P. E. Composites Ltd ISO LARGE YACHT SAFETY WORKING GROUP - STRUCTURAL FIRE PROTECTION PROJECT (presentation only) R Curry, ABS, UK IN-MOULD GEL COATING FOR RESIN TRANSFER MOULDING John Summerscales and Christopher Hoppins, University of Plymouth CONCURRENT ENGINEERING PRINCIPLES APPLIED TO MARINE COMPOSITE STRUCTURES FOR REDUCTION IN PRODUCTION COSTS THROUGH ROBUST DESIGN A Sobey, J Blake, R Shenoi, A Waddams, University of Southampton Marine and Offshore Composites APPLICATION OF COMPOSITES IN SHIPS AND OFFSHORE – A REVIEW AND OUTLOOK J R Weitzenböck, B Hayman, G Hersvik, D McGeorge, P Noury, Det Norske Veritas AS, Norway D M Hill, DNV Ohio, USA A Echtermeyer, Norwegian University of Science and Technology (NTNU), Trondheim SUMMARY The aim of this paper is to show how the use of composites can provide unique solutions and significant commercial benefits to the marine and offshore industry. The main reasons for using composites are to save weight, to reduce maintenance (no corrosion), to achieve complex shapes and tailored properties and multifunctionality. This will be illustrated with a number of examples of successful use of composites on ships and offshore based on DNV’s experience gained from applied research, consulting and technology qualification, verification and certification. These examples include: composite patch repair, composite pressure vessels, tidal turbines, offshore wind turbines, composite bars for reinforcement of marine concrete structures (barges, fixed offshore structures), composite rods as tension members in umbilicals etc, composite risers, and naval ships. 1. INTRODUCTION patches are bonded over the defect and the integrity of the original structure is hence restored. The patch repair Composites have been used in a marine environment for technology can also be utilised to provide upgrades, such many decades. Some of the first large composite ships as life extensions and higher design requirements. were built in the 1970s. The main reasons for using composites are to save weight, to reduce maintenance (no Apart from enhanced fire safety due to the absence of corrosion), to achieve complex shapes and tailored hotwork, composite repairs are also attractive because properties and multifunctionality. The main body of the they are adaptable to virtually any substrate geometry, paper will show many different examples of successful easily conforming to complex shapes and fitting into use of composites on ships and offshore based on DNV’s tight spots. In addition, the anisotropy of composite experience gained from applied research, consulting and materials also affords design flexibility that contributes technology qualification, verification and certification. to cost and property optimisation. These examples include: composite patch repair, composite pressure vessels, tidal turbines, offshore wind Fibre composite materials can be used (i) to patch up turbines, composite bars for reinforcement of marine panels which have lost thickness due to corrosion, (ii) to concrete structures (barges, fixed offshore structures), restore watertight integrity in tanks and other shell composite rods as tension members in umbilicals etc, components by bridging of cracks, due to overload or composite risers and naval ships. fatigue, and of holes, due to corrosion, (iii) to relieve stresses and to arrest cracks at hotspots by bridging cracks in stiffeners, brackets, weldments, etc., and (iv) to 2. COMPOSITE PATCH REPAIR upgrade structures for life extensions or for satisfying altered design requirements, by strengthening decks, Ships and offshore structures often experience damage bulkheads, pillars, etc. (without significantly adding during service such as cracks and corrosion damage. weight to the existing structure). For merchant ships, repair is normally done by welding Marine structures are normally constructed of thick when the ship is in harbour or during dry-docking. plates of very tough structural steel where the critical However, for floating offshore units (FOUs), repairs crack size is considerable. The large critical crack size need to be carried out in the field, and for safety reasons, often implies that it is relatively easy to make a repair parts of the vessel would have to be shut down since that is effective in bridging, and relieving the load at the welding involves hot-work. This means interruption to tip of an advancing crack. The large plate thickness will production and is a costly exercise. Assuming for suggest that the forces being transmitted are very large. example a production rate of 100 000 barrels a day and The key design challenge is to devise a repair where the an oil price of USD 50 per barrel, shutting down an large forces that need to be transmitted from the steel to FPSO for just a day would mean a loss of revenue of the bonded repair patch do not lead to fracture of the USD 5 million. Therefore there is a strong incentive to bondline. For these reasons, the development of bonded avoid the need of hot-work. repairs for marine structures naturally focused on the debond fracture of the bonded assemblies. This contrasts Bonded composite repairs can be used as an alternative with the case of bonded repair of aircraft with much to overcome the hazards of hot-work associated with lighter structures and thinner plating where the key welding. Strong and stiff fibre composite material Marine and Offshore Composites challenge usually is to successfully arrest the crack in the 3. COMPOSITE PATCH REPAIR OF original structure needing repaired. PIPELINE A project recommended practice (RP) has been Composite repairs for metallic pipelines began as a developed that describes requirements for patch repairs fibreglass full circumference wrap. Similar to "wet used in FOUs. To provide flexibility and to fit different layup" fibreglass building applications, these repairs repair needs, the RP defines a range of Repair Classes were safer than welding or hot tapping but still required that can be used depending on the urgency of the repair skilled labour to complete. The technology of the repair and the need for optimisation. The qualification effort evolved to simplify the application process. Precured or increases with the degree of optimisation. Focus is pre-impregnated sleeves, water-activated resins and placed on ensuring resistance to debond fracture using a epoxies, and plastic wrap curing moulds have simplified new method based on [1] an extensive experimental test the repair process and improved its reliability. In the US program and experience from full scale repair there are at least 12 different manufacturers that have demonstrators. similar products. Many use pre-impregnated full wraps, others use wet wraps, and many use water-cured resins. Full-scale repair demonstrators were carried out on actual Extensive tests have been performed to evaluate the FOUs to demonstrate the feasibility of the RP for bonded mechanical strength of composite repairs. Manufacturers composite patch repair. In addition the demonstrators have participated in long term tests to evaluate changes also showed the viability of using bonded composite in performance over time, if any. One vendor of repairs under harsh conditions encountered in oil and gas composite repairs claims to have performed over 100,000 exploration and production environments. Figure 1 repairs in over 60 countries using a variation of the pre- shows the repair that was carried out to arrest a fatigue impregnated wrap product with E-glass fibres. Vendors crack that had developed from the corner of a door claim that the pipelines used in the natural gas industry [from2]. Two other repairs were carried out to restore can maintain pressures of up to 5000 psi (about 350 bars) material loss on heavily pitted deck floor (Figure 2), one with these composite repairs with at least a 20 year on an external deck [2] and one inside a ballast tank [3]. lifespan, but the long term testing that has been performed has not verified this claim. Patches are used when it is impractical for the repair to encompass the full circumference of the component, and the ISO standard recommends that patches be limited to large diameter (greater than 600 mm) pipe work. In addition it is recommended that the patch extend the same distance in axial and circumferential directions. Few products, if any, recommend or advertise the use of a patch, as most prefer to use a full circumference wrap. In the studies presented in [4], the mechanical properties and strength are evaluated after composite repairs have undergone cathodic disbondment testing. Cathodic disbondment has been acknowledged as a concern in the design standards, but there has been little to no data on the performance of composite repairs after cathodic disbondment has been Figure 1 Bonded crack repair installed and completed observed. (from [2[) The ASME PCC-2 standard (Repair of Pressure Equipment and Piping, Non-metallic Repair subgroup) indicates that the repair system shall demonstrate resistance to cathodic disbondment if it is to be employed on cathodically protected surfaces. In addition, it is recommended that the composite system show resistance to low velocity (5 Joule) impacts [5]. In addition, there has been mention of partial encirclement repairs, or patches - such as what is mentioned in the ISO standard for composite repair – but few (if any) companies have demonstrate their use in North America. Less material and time are needed for Figure 2 Bonded repair of corroded deck (from [2]) this type of repair which could offer cost savings. Patches are also relevant for pressure vessels where a full wrap is perhaps impractical, as pressure vessels typically have large diameters. For this reason, the ISO standard Marine and Offshore Composites specifically states that patches are likely better suited A four point bend jig was used to evaluate the effect of only for pipes with large diameters, and equations to cathodic disbondment on the strength and performance of estimate the load transferred from the steel pipe to the the repair, as is shown in Figure 3. It has been shown that composite are cited in the standard [6]. tapering or other stress relieving considerations should be made at the edge of the patch. In addition, it is shown Since strength is the main emphasis for composite repair, that adhesion of the patch to the metal substrate is the performance of the entire metal-composite system fundamental to its function. For full wrap specimens, the has not been extensively addressed with regard to continuous boundary condition of connected edges is corrosion of the substrate, adhesion loss, and cathodic intended to overcome the issue of adhesion to the pipe protection. Standards tend to acknowledge that cathodic surface. It is also shown from the results that the function disbondment (CD) should be considered for these repair of some full-wrap resins is primarily intended for systems, but as of now little effort has been taken to cohesive strength with less emphasis of adhesion on the specify in detail how the present cathodic disbondment surface, though adhesion with the surface prevents standards – which were developed in a coatings context – possible water ingress as well as seepage of moisture into should be adapted to consider the specific properties of the matrix itself, especially if any cracking is present. composite materials. For composite materials, cathodic Adhesion with the surface has relevance to the ability of disbondment tests are so far an adaptation of the ASTM the cathodic protection system to protect the wetted pipe, standards for cathodic disbondment (CD) of coatings. and in environments where the pH is significantly high, the integrity of the resin itself may be an issue. It is However, composite repairs on pipelines have a suggested that if a composite repair is to be implemented component structure that is distinctly different from in environments where coating adhesion is considered of coatings, yet these repairs are implicitly expected to importance, then the suggested test protocols should be serve the same function as a coating. A drilled defect applied to composite materials to also evaluate their creates a precise penetration in a coating that will act as adhesion properties; see also [4]. the controlled defect site for accelerated disbondment testing according to ASTM CD standards, but the shortfall in this approach with regard to composites is 4. OFFSHORE COMPOSITE PRESSURE that there are few field conditions that will result in a VESSELS pinhole-like defect. The conditions that cause a puncture or tear in a coating will cause an impact and micro- Composite pressure vessels have become an interesting fracture cracks in a composite. A composite is generally alternative to steel pressure vessels. They are lighter and much more durable than a coating and can withstand have much better corrosion resistance. Cost wise they much greater impact energy. The composite system is also seem to be competitive. more resistant to impact, thicker, has greater cohesive integrity, and its cured resin matrix is often stronger than Composite pressure vessels are a well established as fuel a coating. But composites are more prone to brittle tanks for cars and busses using compressed natural gas fracture than coatings which are typically more (CNG). This application is covered by various national malleable. If cathodic disbondment is to be tested for a and international standards /NVE, ISO etc./. composite system, a drilled defect is unrealistic; an impact is more relevant to field conditions. Transporting CNG on large ships or on barges has been discussed over the last years and various concepts have been developed. Using large composite pressure vessels instead of steel pressure vessels could be a promising alternative. The existing standards are not applicable for this application. The large pressure vessels exceed the size limit given in the car standards. This may look like just a formality, but liner, boss and laminate design meet new challenges for very large vessels. In addition, the production related issues require new thinking. Another important aspect is that the standards related to automotive applications assume a certain number of loading cycles within the lifetime of the pressure vessel. This number of cycles is unfortunately not explicitly given. It is very different for CNG transport where typically loading/unloading happens only once a week. This requires a different and more specific fatigue analysis related to the actual project. A special set of rules has been written to address exactly this application Figure 3 A jig connected to a stress frame was used to [7]. bend the 12”x6”x0.1875” plates. Marine and Offshore Composites Composite pressure vessels have recently been used as consequences of production defects. A major challenge is accumulator bottles in heave compensation systems of to develop cost-effective ways to ensure that production risers and offshore cranes. These applications are defects do not cause unacceptable reductions in exposed to high number of pressure cycles with variable equipment strength and lifetime, given that inspection of load sequences and amplitudes. This requires again a large wind power structures is often problematic, careful evaluation of fatigue conditions. In addition especially when they are installed offshore. A current serviceability shall be ensured at tropical and arctic aim of DNV is to develop ways of introducing improved conditions. Such pressure vessels could be qualified by damage tolerance into the design and manufacture of using the DNV standard for composite components [8] in wind turbine blades, using, where appropriate, some of combination with the rules for CNG ships [7]. the concepts that have been established in the aircraft industry. 5. OFFSHORE WIND TURBINES 6. TIDAL TURBINES By far the most common type of wind energy converter in current use is a horizontal-axis turbine with blades of Tidal energy converters are at a much earlier stage of fibre composite materials. This turbine concept is development than wind energy converters. There are expected to remain as the major provider of wind power many different concepts, but most are still in the in the foreseeable future. The largest blades currently in development or prototype stages. Several involve major series production are approximately 62 m long. The components, such as turbine blades, in composites. The DNV Offshore Standard for Design and Manufacture of design and qualification of composite blades for tidal Wind Turbine Blades, DNV-OS-J102 [9], applies to turbines present several significant challenges, the main wind turbines for both offshore and onshore installation. one being that no standards or design rules currently It covers design, manufacturing and testing of blades and exist. The certification process (which normally consists is based on more than twenty years’ experience of blade of confirming that a component or system complies with certification. a specified standard) has to reflect this. The approach used by DNV is described in the Service Specification The standard represents, in particular, a basis for type [12] and is largely based on the procedures for certification of blades and provides a detailed qualification of new technology described in the DNV interpretation of IEC WT 01 [10]. It also provides a Recommended Practice [13]. Typically such a process guideline for designers, manufacturers, operators, and yields, at different stages of the development, a regulators of wind turbines and a technical and Statement of Feasibility, a Prototype Certificate, a contractual reference document between clients, Conditioned Type Certificate, a Type Certificate and contractors, suppliers, consultants and third parties. finally a Project Certificate. Wind turbine blades are quite complex structures. In the absence of a specific standard, the wind turbine Although methods and tools for analysis of composite blade standard [9] is quite extensively used as an aid to structures have improved greatly during the past few designing and qualifying tidal turbine blades, though it years it is still necessary to include a significant amount must be recognised that the environments in which they of testing in the qualification process. This involves operate is totally different. For some aspects it is testing of material coupons, structural elements and preferable to refer to the Offshore Standard for details, and normally just one full-scale blade. Clearly Composite Components [8]. testing only one single blade has limited value, but it does reduce the likelihood that gross errors or omissions 7. COMPOSITE BARS FOR go undetected. Criteria for selection of the test blade and REINFORCEMENT OF MARINE optimisation of the testing procedures are topics of CONCRETE STRUCTURES (BARGES, discussion. The blade is normally tested first with four FIXED OFFSHORE STRUCTURES) cases of static loading in each of the principal directions, then subjected to fatigue loading, and finally to a repeat The use of FRP bars as concrete reinforcement was first of the static loading test. demonstrated in the 1950s with a resurgence in interest in the 1980s. Since then, numerous applications have been Materials challenges for wind turbine blades have been demonstrated in the US, Europe and Asia. A more discussed in detail by Hayman et al. [11]. Many detailed overview is provided by ACI [14]. challenges are related to the use of fibre composites in increasingly large blades and increasingly hostile DNV was contracted by ReforceTech AS to qualify a environments. Among these are achieving adequate new type of FRP bars using basalt fibres and a new stiffness to prevent excessive blade deflection, manufacturing process for use as reinforcement for preventing buckling failure, ensuring adequate fatigue concrete structures. Criteria for assessment of the bars in life under variable wind loading combined with service conditions as well as the performance and gravitational loading, and minimising the occurrence and behaviour of concrete elements reinforced with these Marine and Offshore Composites bars were developed [15]. A Guideline for such benefits elsewhere. Fibre polymer composites were first structures is developed and planned to be incorporated in introduced into naval ships because of their non- DNV's offshore standard for concrete structures. This magnetic properties and suitability for use in mine permits the design and construction of concrete structures countermeasure vessels. In non-military applications reinforced with basalt fibre composite bars. The main light weight and suitability for use in high speed vessels advantages compared to conventional concrete structures have been the driving force. In the past two decades, are especially in Scandinavia, several lightweight high-speed naval ship concepts have been developed and put into • Low weight and high strength. practice. • Concrete dimensions and weight will be less due to reduced need for concrete cover. Classification services related to naval ships have been • The bars do not corrode and can be positioned introduced by most of the major classification societies. close to the surface. In the case of DNV [19] the rules have been based on, • Meshes with small bar diameter may be placed and combined with, the Rules for High Speed Craft, at low cover to control crack widths. reflecting the fact that in many navies there has been a need for a streamlined and efficient approval system for • As the bars are not sensitive to corrosion, larger small and medium-sized ships that do not readily fit into cracks may be accepted than what is acceptable the standard class rules for conventional ships. As the for steel reinforced concrete. DNV Rules for HSC have traditionally included full • The bars can be pre-stressed to a relative low coverage of composite hull structures, of both sandwich values and still retain the pre-stressing level. and stiffened single-skin construction, the Rules for Classification of High Speed, Light Craft and Naval Surface Craft can readily be used for classifying naval 8. RODS AS TENSION MEMBERS IN ships of composite construction. This has been UMBILICALS demonstrated in recent years as DNV has classed the Danish naval fleet including vessels of the “Standard Pultruded composite rods have very high axial stiffens Flex” type and smaller patrol boats of the Holm Class and strength at low weight. For this reason such rods (see also Figure 4). were qualified as tethers for tension leg platforms or other floating structures in deep water service [16]. The qualification was based on the general standard for composite components [8] and the recommended practice for qualification of new technology [13]. The main application of this technology has however been deep water umbilicals, where the carbon rods are used to stiffen the umbilical and protect the other components from bending damage. Similar to the risers, the end fitting is the main design and qualification challenge. 9. COMPOSITE RISERS Composite risers have been considered for deep water applications for many years, but have so far not had commercial success. A big qualification program was Figure 4 Diana – class patrol boats from the Danish carried out in the late 90s resulting in a prototype riser navy; from [20] joint being installed on the Heidrun platform in the North Sea [17]. The experience was taken further and Many composite structures, in order to reduce weight, generalized in a recommended practice for composite have become highly optimised to the extent that it has risers [18]. The main challenge in designing and making been necessary to consider carefully their damage a composite riser are the end fittings of the joints. The tolerance; this is especially important when composite Heidrun riser joint passed all qualification tests and has vessels are operated at high speeds in a harsh or been used successfully in service. potentially dangerous environment. For the case of naval vessels of composite sandwich construction extensive work has been done in recent years to improve the 10. NAVAL SHIPS AND HIGH SPEED CRAFT detection, characterisation, assessment and repair of both production defects and in-service damage [21, 22]. Such Naval ships have for some decades represented an studies are still ongoing so that crews and others extremely important marine application area for involved in the operation of such vessels will be able in composites and a great deal of research and development the future to make both quick and more thorough has been performed in this context and led to appreciable assessments of the likely consequences of damage, and to Marine and Offshore Composites decide on the necessary actions to be taken. Knowledge vehicle ramps and the like. Although at present the of the reduction in residual strength of a sandwich panel application of SPS is mainly confined to repair, its use in in the presence of local damage of a given type and newbuilding is expected to grow in the future. extent forms a key element in such a system; Figure 5 shows a typical strength reduction curve for GRP laminates or sandwich face sheets when subjected to in- plane tensile loading following the introduction of face sheet impact damage represented by holes of varying sizes [23]. This type of information is also valuable for the assessment of similar damage experienced by other structures such as wind turbine blades. 1.0 Rl 0.9 Test Laminate Type LA4 or 0.8 Test Laminate Type LB4 ct a Average stress model, ao = 5 mm n f0.7 o cti0.6 Figure 6 The Sandwich Plate System: 2 steel plates u d0.5 bonded to an elastomeric core e h r0.4 gt n e0.3 str al 0.2 c Lo0.1 0.0 0 10 20 30 40 50 Hole diameter (mm) Figure 5 Local strength reduction factors for laminates with holes under tensile loading – test results and average stress model (from [23]). Figure 7 SPS newbuilding panel (top) and conventional 11. SPS CLASS NOTE stiffened steel plate (bottom) In today's competitive shipping industry, reduction of In response to this new situation, Det Norske Veritas production and maintenance costs and enhancement of (DNV) has initiated the development of classification safety and environmental protection are vital. A new rules for the application of steel sandwich panel trend towards the use of novel, innovative sandwich construction of the SPS type. The goal of the document is structures has emerged, and is contributing towards a to provide a framework for the classification of ship new direction for ship structure technology. structures with such materials. The new rules will cover both ship repair and newbuilding and will consist of Several types of metal sandwich construction have seven main sections: appeared, including extruded aluminium, laser-welded steel and steel-elastomeric systems. Key motivations for 1. General using steel and aluminium sandwich systems are to 2. Materials and manufacturing improve safety and reliability, to save weight and space, 3. New construction and to increase efficiency of fabrication and 4. Overlay construction maintenance, while working with a known material. 5. Connections Irrespective of these general benefits, each sandwich 6. Fire safety concept shows specific advantages and disadvantages as 7. Examples and guidance well as very different degrees of maturity and popularity. Section 1 provides general information: purpose, scope, A sandwich concept that has succeeded in overcoming applicability, corrosion margins, new class notations, the cautious nature of the maritime industry is the fundamental principles behind the formulations and the Sandwich Plate System (SPS, shown in Figure 6 and documentation to be submitted for approval. Figure 7). This is a composite material technology in which two steel plates are bonded to a dense elastomeric core. Over the last decade it has established itself as one of the preferred reinstatement technologies for decks, Marine and Offshore Composites Section 2 specifies requirements to the quality of the with 10 mm faces and 35 mm core, clamped boundaries, materials (e.g. type approval certificate) and panel compared with parabolic curve manufacturing process. Section 3 and 4 lay down requirements for new 12. FREE FALL LIFEBOATS construction and overlay applications, respectively. In particular, formulas for capacity under separate loading Composite materials have been extensively used in free cases and combined loading cases are given. fall life-boats in the past. Formulations are based on specific failure mechanisms of SPS type panels. The free fall lifeboats currently in place on fixed and floating structures on the Norwegian Continental Shelf Section 5 contains pre-approved construction details for may have weaknesses when it comes to structural safety, overlay and newbuilding construction. human loads and headway, when the boats are used for emergency evacuations in bad weather. Shortcomings of Section 6 gives requirements and guidance for existing lifeboat designs in these respects were revealed compliance with Ch.II-2 Reg.17 of SOLAS (Safety of through a number of incidents observed in 2005 during Life at Sea) [24]. These are DNV’s interpretation of on-site drop testing of some of the lifeboats [26]. SOLAS and are meant as a further detailing and clarification of the SOLAS requirements and guidelines. In response to this, DNV has developed an offshore standard for such lifeboats with improved load Section 7 illustrates the applicability of the new rules for definitions and up-to-date criteria for composite several typical components. It aims to demonstrate the structural design capacity checks in a modern partial use of the new rules, their flow and philosophy, and to safety factor format [27]. point to important aspects to consider. The research and development programme to develop the 13. SUPERSTRUCTURES IN SHIPS new classification rules will be finalised in 2010. The publication of the new set of rules is scheduled for The use of composites in superstructure modules has January 2011. been investigated in a number of research projects showing promise of considerable weight-saving in excess In parallel with the rule development DNV is studying of 50% of the weight of a steel design for the module. the ultimate capacity of SPS-type sandwich panels under Adequate fire safety has been demonstrated via a separate and combined loading types, in collaboration rigorous risk assessment [28]. The key challenge for with the University of Oslo [25]. The study considers a using this new technology in practice is to convince the wide range of panel lengths and widths and of face and relevant approval authority that equivalence to steel has core thicknesses and focuses especially on the been demonstrated according to the detailed combination of transverse pressure loadings with in- requirements of SOLAS [24]. plane shear and compression loads. The primary objective is to develop interaction curves or formulae for both clamped and simply-supported, rectangular panels. 14. CERTIFICATION OF MATERIALS A tentative interaction curve for a panel with combined lateral pressure and in-plane shear loading is shown in As part of ship classification, DNV also certifies all Figure 8. materials, components and systems relevant to the safe operation and quality of ships. The design assessment, type approvals and production assessments ensure that 1 systems and components are fit for their purpose, and FE fulfil the requirements of DNV Rules or specific Parabola 0.8 recognised standards. Material certification means ult Q issuing a certificate stating that the material complies Q/0.6 with the requirements of DNV rules. For the most r important components onboard DNV classed vessels, a e0.4 DNV certified material shall be used. Material h S certification usually requires approval of the 0.2 manufacturer. Typically, certification is based on testing of the material, performed under the attention of a 0 surveyor. Type approval (TA) is a procedure for design 0 0.2 0.4 0.6 0.8 1 assessment of products and systems, and is an alternative Lateral pressure p/p to the “case by case” design assessment. TA is defined ult as: Approval of conformity with specified requirements Figure 8 Points on interaction curve for combined lateral on the basis of systematic examination of one or more pressure and in-plane shear loads for 2 m square panel Marine and Offshore Composites specimens of a product representative for the production. IMO Chapter II-2 Part F Regulation 17 on Alternative The basis for issuing a TA certificate is DNV Rules, Design and Arrangements opens up for radical new Offshore Codes and TA Programmes. When approval of solutions. However, experience so far indicates that the conformity is based on standards or specific requirements use and implementation is rather difficult and time other than the DNV Rules, the term “Type Examination” consuming in the case of composite materials. Some of shall be used instead of “TA”. the applications considered under Regulation 17 include composite superstructures. The material certification activities cover the constituent materials of FRP composites and sandwich materials. The need to reduce operating costs and carbon footprint The approval procedures are specified in the respective requires that ship structures become lighter. A soon to be type approval programmes and the test results are published study by DNV [30] indicates that large scale available on the internet [29]: use of composites in e.g. pipes on a containership can yield weight savings of many hundreds of tons. • Glass Fibre Reinforcements • Polyester Resin, Vinylester Resin, Gelcoat and These two examples clearly illustrate that the use of Topcoat composites will increase further in the future. To be • Sandwich Core Materials successful, new applications need to address not only the • Sandwich Adhesives technical problems but also regulatory issues, including both requirements from class and flagstates • Adhesives • Epoxy Systems • Aramid Fibre Reinforcements 16. REFERENCES • Composite Drive Shafts and Flexible Couplings • Carbon Fibre Reinforcements • Elastomeric Core Materials for Use in Sandwich 1. McGeorge D. Inelastic fracture of adhesively bonded Plate System (SPS) or Similar overlap joints. Eng Fract Mech, 2009. Further certification activities include FRP pipes used 2. McGeorge D, Echtermeyer A T, Leong K H, Melve B, e.g. for ballast water tanks and the approval of Robinson M, Fischer K P, ‘Repair of floating offshore manufacturers of “filament wound fibre reinforced units using bonded fibre composite materials’, Submitted thermosetting resin tube for machine components and to Composites Part A – Special Issue on Repair, 2009. special pressure system components”. doi:10.1016/j.compositesa.2009.01.015 It is expected that the continued interest for lightweight 3. Meniconi L, McGeorge D, Pedersen A. Structural ship structures for increased fuel efficiency will lead to repair at a production platform by means of a composite increased demand for certification of materials, albeit at a material patch. To be presented at OTC 2010. modest rate of growth as many of the main suppliers are already certified. 4. Hill, D., Sridhar N., Denzine, R., and G. Snyder, "Mechanical Properties and Performance of Composite- Reinforced Steel Pipelines in Wet Environments with 15. CONCLUSIONS AND OUTLOOK Cathodic Protection", NACE Corrosion Conference and Expo, March 2010. San Antonio TX USA. Paper # This paper has illustrated how composites are being for 14670 many demanding applications in marine and offshore structures. There have been significant efforts to develop 5. ASME Standard PCC-2 Repair of Pressure Equipment further the technology as well as the regulatory aspects of and Piping, 2008. Sub section: Non-metallic Composite it. While we observe steady growth one also has to Repair Systems for Pipelines and Pipework. acknowledge that new solutions take a long time to implement. Usually there are concerns about long-term 6. ISO/TS 24817: 2006. Petroleum, Petrochemical, and performance and how to document it. Natural Gas Industries: Composite Repairs for Pipework – Qualification and Design, Installation, Testing, and Future applications of composites will be driven by some Inspection. of the following market trends: 7. Rules for Classification of Ships Pt.5 Ch.15, “CNG • Reduce structural weight to improve fuel Carriers, Scantlings and Testing of Composite Type efficiency and reduce the environmental footprint Cargo Tanks” of the ship. • More efficient and reliable facilities for renewable 8. DNV Offfshore Standard, DNV-OS-C501 Composite energy generation Components • Ultradeep water exploration of hydrocarbons.