Table Of ContentMARINE 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.
