SIST EN 13923:2006
(Main)Filament-wound FRP pressure vessels - Materials, design, manufacturing and testing
Filament-wound FRP pressure vessels - Materials, design, manufacturing and testing
This European Standard specifies the requirements for the design including raw materials, calculation, manu-facturing including composite materials, and testing of seamless Glass Reinforced Plastic (GRP) pressure vessels with protective layer, using only multi-directional filament winding, made in a factory and for use above ground and for storage and processing of fluids.
This European Standard covers vessels subject to pressures below 20 MPa and temperatures between
- 30 °C and 120 °C.
Excluded from this European Standard are transportation vessels, double wall vessels, vessels under nega-tive pressure, vessels which are subjected to the risk of explosion or failure of which may cause an emission of radioactivity.
Fadengewickelte Druckbehälter aus textilfaserverstärkten Kunststoffen - Werkstoffe, Konstruktion, Herstellung und Prüfung
Diese Europäische Norm enthält Anforderungen für die Konstruktion, einschließlich Ausgangswerkstoffe, Berech-
nung, Herstellung, einschließlich Verbundwerkstoffe sowie die Prüfung von fabrikmäßig hergestellten oberirdischen
GFK-Druckbehältern mit Schutzschicht, mit ausschließlich multidirektionaler Fadenwicklung zur Lagerung und Ver-
arbeitung von Fluiden.
Diese Europäische Norm behandelt Behälter für den Betrieb mit einem Druck unter 20 MPa und Temperaturen
zwischen -30 °C und 120 °C.
Nicht in dieser Europäischen Norm enthalten sind Transport- und Doppelmantelbehälter sowie Behälter unter
negativem Druck, Behälter, bei denen Explosionsgefahr besteht oder bei deren Versagen Radioaktivität freigesetzt
werden kann.
Récipients sous pression en PRV par enroulement filamentaire - Matériaux, conception, fabrication et essais
La présente Norme européenne spécifie les exigences relatives a la conception, y compris les matériaux de
base, au calcul, a la fabrication y compris les matériaux composites, et aux essais des récipients sous
pression en plastique renforcé de fibres de verre (PRV) sans soudure, utilisant uniquement l’enroulement
multi-directionnel des filaments, avec couche de protection, fabriqués en usine, implantés hors sol, destinés
au stockage ou au traitement de fluides.
La présente Norme européenne couvre les récipients soumis a des pressions inférieures a 20 MPa et a des
températures comprises entre - 30 °C et 120 °C.
Sont exclus de la présente Norme européenne les récipients pour le transport, les récipients a double paroi,
les récipients soumis a dépression, les récipients qui sont sujets a un risque d'explosion ou une défaillance
qui peut provoquer une émission radioactive.
Monofilno navite tlačne posode iz FRP – Materiali, načrtovanje, izdelava in preskušanje
General Information
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Filament-wound FRP pressure vessels - Materials, design, manufacturing and testingSUHVNXãDQMHRécipients sous pression en PRV par enroulement filamentaire - Matériaux, conception, fabrication et essaisFadengewickelte Druckbehälter aus textilfaserverstärkten Kunststoffen - Werkstoffe, Konstruktion, Herstellung und PrüfungTa slovenski standard je istoveten z:EN 13923:2005SIST EN 13923:2006en23.020.30ICS:SLOVENSKI
STANDARDSIST EN 13923:200601-marec-2006
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13923November 2005ICS 23.020.30 English VersionFilament-wound FRP pressure vessels - Materials, design,manufacturing and testingRécipients sous pression en PRV par enroulementfilamentaire - Matériaux, conception, fabrication et essaisFadengewickelte Druckbehälter aus textilfaserverstärktenKunststoffen - Werkstoffe, Konstruktion, Herstellung undPrüfungThis European Standard was approved by CEN on 22 September 2005.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2005 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13923:2005: E
EN 13923:2005 (E) 2 Contents Page Foreword.3 Introduction.4 1 Scope.5 2 Normative references.5 3 Terms and definitions.5 4 Symbols and abbreviated terms.7 5 General.8 6 Materials.8 6.1 General.8 6.2 Raw materials.8 6.3 Chemical resistance.9 6.4 Characteristics values for calculations.9 7 Design.11 7.1 General.11 7.2 The design factor.11 7.3 Permissible strain.13 7.4 Stress resultants.14 8 Design analysis method A.16 8.1 General.16 8.2 Calculations.16 8.3 Prototype testing.17 9 Design analysis method B.18 9.1 Calculation.18 10 Design documentation.20 11 Manufacturing.20 11.1 Filament winding.20 11.2 Protective layers.21 11.3 Manufacturing specifications.22 12 Final acceptance testing.22 12.1 General.22 12.2 Acceptance testing for filament wound vessels.22 12.3 Hydrostatic pressure test.23 12.4 Test report.24 Annex A (normative)
Fabrication of flat filament wound test specimens.25 Annex B (informative)
Laminate Theory.27 Annex C (normative)
Extrapolation method for long term behaviour.34 Annex D (informative)
Calculation example.37 Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 97/23/EC.40 Bibliography.41
EN 13923:2005 (E) 3 Foreword This European Standard (EN 13923:2005) has been prepared by Technical Committee CEN/TC 210 “GRP tanks and vessels”, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by May 2006, and conflicting national standards shall be withdrawn at the latest by May 2006. This European Standard falls under the Pressure Equipment Directive (PED) and supports essential require-ments of this EC Directive. For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this European Standard. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Den-mark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxem-bourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EN 13923:2005 (E) 4 Introduction This European Standard specifies two design methods for filament wound GRP pressure vessels. In this European Standard only the winding is considered in the calculation of the strength and the stiffness of the shell. Method A, describes the calculation of the reinforcement of the cylindrical shell and the end domes based on netting theory. The design is verified by prototype testing. Method B, describes the calculation of the reinforcement of the cylindrical shell and the end domes based on laminate theory. The design and manufacture of filament wound GRP pressure vessels involve a number of different materials, such as resins, thermoplastics and reinforcement fibres. It is implicit that vessels conforming to this European Standard should be made only by manufacturers and operators who are competent and suitably equipped to fulfil all requirements, using materials manufactured by competent and experienced material manufacturers. This European Standard specifies stress and strain limits and the requirements for the acceptance testing.
EN 13923:2005 (E) 5 1 Scope This European Standard specifies the requirements for the design including raw materials, calculation, manu-facturing including composite materials, and testing of seamless Glass Reinforced Plastic (GRP) pressure vessels with protective layer, using only multi-directional filament winding, made in a factory and for use above ground and for storage and processing of fluids. This European Standard covers vessels subject to pressures below 20 MPa and temperatures between
– 30 °C and 120 °C. Excluded from this European Standard are transportation vessels, double wall vessels, vessels under nega-tive pressure, vessels which are subjected to the risk of explosion or failure of which may cause an emission of radioactivity. 2 Normative references The following referenced documents are indispensable for the application of this European Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 13121-1:2003, GRP tanks and vessels for use above ground — Part 1: Raw materials — Specification conditions and acceptance conditions EN 13121-2:2003, GRP tanks and vessels for use above ground — Part 2: Composite materials — Chemical
resistance prEN 13121-3:2004, GRP tanks and vessels for use above ground — Part 3: Design and work-manship EN ISO 527-4, Plastics — Determination of tensile properties — Part 4: Test conditions for isotropic and
orthotropic fibre-reinforced plastic composites (ISO 527-4:1997) EN ISO 14129, Fibre-reinforced plastic composites — Determination of the in-plane shear stress/shear strain response, including the in-plane shear modulus and strength, by ± 45° tension test method (ISO 14129:1997) EN ISO 75-2:2004, Plastics — Determination of temperature of deflection under load — Part 2: Plastics and ebonite and long-fibre-reinforced composites (ISO 75-2:2004) EN ISO 75-3, Plastics — Determination of temperature of deflection under load — Part 3: High-strength ther-mosetting laminates (ISO 75-3:2004) ISO 2602, Statistical interpretation of test results — Estimation of the mean — Confidence interval 3 Terms and definitions For the purpose of this European Standard, the following terms and definitions apply. 3.1 manufacturer organisation that manufactures the vessel in accordance with this European Standard 3.2 material manufacturer organisation that manufactures the specific material (e.g. resin, glass fibre or catalyst). The material manufac-turer may also be the “supplier” 3.3 purchaser organisation or individual that purchases the vessel
EN 13923:2005 (E) 6 3.4 supplier organisation that supplies materials or products to the manufacturer for use in manufacturing the vessel. The supplier may be either the material manufacturer or an intermediary 3.5 pressure vessel housing designed and built to contain fluids under pressure including its direct attachments up to the coupling point connecting it to other equipment. A vessel may be composed of more than one chamber 3.6 protective layer chemical resistant layer (CRL) or a thermoplastic lining (TPL) in accordance with Clause 4 of
EN 13121-2:2003, intended to serve as a barrier against chemical attack of the structural laminate and to pre-vent leakage 3.7 pressure pressure relative to atmospheric pressure, i.e. gauge pressure. As a consequence, vacuum is designated by a negative value 3.8 maximum allowable pressure PS maximum operating pressure for which the equipment is designed, as specified by the manufacturer. This is identical to the design pressure 3.9 maximum/minimum allowable temperature TS maximum/minimum temperature for which the equipment is designed, as specified by the manufacturer. The maximum allowable temperature is identical to the design temperature 3.10 lamina ply or layer of glass reinforced thermosetting resin 3.11 laminate composite structure consisting of one or more lamina 3.12 filament winding production technique for winding of continuous filaments of glass fibre with the specified resin system applied in a systematic manner and cured on a mandrel or other supporting structure 3.13 chemical resistant layer (CRL) protective layer in accordance with 4.3 of EN 13121-2:2003 3.14 thermoplastic lining (TPL) protective layer in accordance with 4.4 of EN 13121-2:2003 3.15 contact layer layer to increase adhesion between TPL and structural laminate 3.16 hoop winding winding for which the fibre direction is perpendicular to the rotation axis of the vessel
EN 13923:2005 (E) 7 3.17 helical winding winding for which the angle between the fibre direction and the rotation axis is not 0° or 90° 3.18 prototype pressure vessel with the same diameter and end domes, manufactured with the same material and winding specifications using the same manufacturing techniques as a production vessel, but used only for testing pur-poses 3.19 pigment component added to change the natural colour of the resin 4 Symbols and abbreviated terms For the purpose of this European Standard, the symbols and abbreviated terms shall be used according to
Table 1. Table 1 — Symbols and abbreviated terms Symbol Term Unit b width mm h height mm mf fibre content by mass — PS design pressure MPa pcrit critical pressure MPa r radial co-ordinate mm rp radius of polar opening mm t wall thickness mm th thickness of the helical windings mm tc thickness of the circumferential windings mm wi weight of part i of the shell N A material weakening factor — A1, . A5 partial design factors — C shape factor — Da internal diameter of winding laminate mm E1, E modulus of elasticity in the fibre direction MPa E2 modulus of elasticity perpendicular to the fibre direction MPa l length of shell mm K design factor — Mf fibre reinforcement content per square meter kg/m² Mw wind moment on the shell Nmm Mφ bending moment in longitudinal direction Nmm/mm Mθ bending moment in circumferential direction Nmm/mm Nφ stress resultant in longitudinal direction N/mm Nθ stress resultant in circumferential direction N/mm P probability % R radius of a end-dome mm S safety factor — TSHL Tsai-Hill criterion — Vf fibre volume fraction — α winding angle ° ρf density of the fibre kg/m³ ρr density of the resin kg/m³
EN 13923:2005 (E) 8 Table 1 (concluded) σ stress MPa τ shear stress MPa ε strain % εn strain normal to the fibre direction % υ12 Poisson’s ratio — TS design temperature °C HDT heat deflection temperature °C εmax maximum allowable strain % εlim strain limit % G in-plane shear modulus MPa Xt ultimate longitudinal tensile strength MPa Xc ultimate longitudinal compressive strength MPa Yt ultimate transversal tensile strength MPa Yc ultimate transversal compressive strength MPa Ss in-plane shear strength MPa 5 General The manufacturer shall obtain from the purchaser sufficient information to undertake the product design and construction in accordance with the requirements of this European Standard: vessel volume and the vessel fluid; maximum operating pressure including the alternating pressure; maximum operating temperature including the alternating temperature; additional data shall be supplied on any stresses occurring as a result of operation (pressures, pipe work, extremes of temperature, fluids, wind etc.), sequential filling or emptying of the vessel, the application and removal of the pressure. 6 Materials 6.1 General The composite materials, hereinafter referred to as “composites” are characterised by matrix materials based on thermosetting resins by the quantity and order of reinforcing fibre and by the laminating or the moulding process for the protective layer and the winding process for the structural laminate. The components of composites hereinafter are referred to as “raw materials”. Raw materials acceptance con-ditions and usage conditions shall be in accordance with EN 13121-1 and the exceptions or restrictions listed in 6.2. The chemical resistance of composites shall be in accordance with EN 13121-2 and the exceptions or
restrictions are listed in 6.3. 6.2 Raw materials 6.2.1 Reinforcements In the structural laminate continuous roving in accordance with 6.6 and 9.11 of EN 13121-1:2003 shall only be used.
EN 13923:2005 (E) 9 In the CRL chopped strand mats in accordance with 6.3 and 9.9 of EN 13121-1:2003 or chopped roving in accordance with 6.6 and 9.11 of EN 13121-1:2003 shall be used. 6.2.2 Resins In the structural laminate UP-resins in accordance with 4.1, 4.2, 9.1 and 9.2 of EN 13121-1:2003, VE-resins in accordance with 4.1, 4.3, 9.1 and 9.2 of EN 13121-1:2003 and EP-resins in accordance with 4.1, 4.4, 9.1 and 9.3 of EN 13121-1:2003 shall be used. 6.2.3 Thermoplastic lining materials In addition to those thermoplastic materials listed in 8.1 of EN 13121-1:2003, other thermoplastic materials may be used if they meet the requirements of workmanship and service conditions. Specifications and techno-logical data for these materials shall be confirmed by the thermoplastic material manufacturer according to the general requirements in Clause 8 and 9.12 of EN 13121-1:2003. The range of thickness of thermoplastic linings shall be specified by the manufacturer. Using PE linings the minimum shear strength to the structural laminate shall be 5 N/mm2 when tested at maximum operating temperature in accordance with D.8 of prEN 13121-3:2004. If necessary, a contact layer to the structural laminate may be used. 6.2.4 Pigments Pigments are allowed in the structural laminate only in case of vessels designed according to method A. The amount of pigment is restricted by recommendations from the supplier or resin manufacturer. 6.3 Chemical resistance 6.3.1 Reinforcements Type of fibre, listed in 6.2.1, shall be in accordance with A.3 of EN 13121-2:2003. 6.3.2 Resins Resins, listed in 6.2.2, shall be used in accordance with Clause 5 of EN 13121-2:2003. EP-resins are only to be used according to 5.3, 5.5 or 5.6 of EN 13121-2:2003. 6.3.3 Thermoplastic lining material Thermoplastic materials shall be used in accordance with Clause 5 of EN 13121-2:2003. Other thermoplastics are only to be used according to 5.4, 5.5 or 5.6 of EN 13121-2:2003. 6.4 Characteristics values for calculations 6.4.1 General The manufacturer shall determine the required mechanical properties of all reinforcing lamina. There are four elastic constants and five strength constants that can be determined for a lamina. For design calculations only the constants E1, E2, G, ν12, Xt, Xc, Yt, Yc and Ss (for definitions see Clause 4) needed shall be determined. The mechanical properties of the individual lamina shall be used for the design calculations of the laminate
according to Clause 8 and Clause 9.
EN 13923:2005 (E) 10 6.4.2 Test specimen Test specimen for filament wound laminate shall be made from a unidirectional wound flat panel made according to Annex A. The test specimen shall be made from the same materials as determined in the production specifica-tion. The flat test specimen shall have a representative thickness, the curved test specimen shall have a represen-tative thickness to diameter ratio. The fibre content of the test specimen shall be as specified in Clause 8 and Clause 9 with a tolerance of + 0 % and – 10 %. Winding patterns shall be achieved to within ± 5° of the speci-fied angle. The number of test specimen shall be in accordance with the value of the partial design factor for dis-persion (see 7.2.2). 6.4.3 Elastic properties 6.4.3.1 E1-modulus The E1-modulus for a filament wound laminate shall be determined either by performing an uniaxial tensile test according to EN ISO 527-4 on a flat test panel according to Annex A. The Poisson ratio ν12 shall be
determined from the same test, from the measurement of longitudinal and transverse strains. 6.4.3.2 E2-modulus The E2-modulus for a filament wound laminate shall be determined by performing a uniaxial tensile test
according to EN ISO 527-4 on a test panel according to Annex A. 6.4.3.3 G-modulus The shear modulus G for a filament wound laminate shall be determined by performing a shear test according to EN ISO 14129. 6.4.4 Strength properties 6.4.4.1 The longitudinal strength The longitudinal strength X for a filament wound laminate shall be determined by performing a uniaxial tensile test according to EN ISO 527-4 on a test panel according to Annex A. 6.4.4.2 The transverse strength The transverse strength Y for a filament wound laminate shall be determined either by performing a uniaxial
tensile test according to EN ISO 527-4 on a test panel according to Annex A. 6.4.4.3 The shear strength The shear strength Ss for a filament wound laminate shall be determined by a shear test according to
EN 14129 on a flat test panel. 6.4.5 Test report The results of the tests in accordance with 6.4.3 and 6.4.4 shall be documented in a report which shall become a part of the "Design documentation", as described in Clause 10.
EN 13923:2005 (E) 11 7 Design 7.1 General This European Standard contains two methods for the design of filament wound GRP pressure vessels. The thickness of the vessel parts designed by method A shall be determined by the calculation method given in Clause 8 and the design shall be confirmed by prototype testing according to 8.3. The thickness of the vessel parts designed by method B shall be determined by the calculation method given in 9.1. Filament wound pressure vessels shall be designed so that any developing distortions and changes in mate-rial properties do not impair the safety of the component part, not even during long-term stressing. This shall be approved in tests according to Clause 6 and Clause 12. The design shall take into account the maximum difference in fluid pressure which can occur under the
service conditions as specified in the design specification, between the inside and the outside of the vessel wall or between two chambers. The protective layer shall not be included in the determination of the required wall thickness. However, the weight of the protective layer shall be taken into account when determining loading other than pressure. The protective layer shall be designed so that it extends completely through all openings in the vessel. 7.2 The design factor 7.2.1 General The allowable stresses in each layer of the load-bearing material are derived from the characteristic values for elasticity and strength, the material-independent safety factor S and the partial design factors to account for the influence of inhomogeneities and dispersion (A1), chemical environment (A2), design temperature versus heat resistance (A3) and long term behaviour (A5). The protective layer shall be ignored in strength calcula-tions. The design factor K shall be determined from the Equation (1). K = S × A1 × A2 × A3 × A4 × A5
(1) The safety factor S shall be 2,0. The partial design factors A1 to A5 in Table 2 apply only if it can be demonstrated that the requirements accor-ding to 6.4 and the conditions given in 7.2.2 to 7.2.6 are strictly observed. The partial design factors A1 to A5 may be reduced if justified by long-term tests on representative material samples or by strain measurements or by long-term pressure tests on representative vessel samples and if such a reduction is confirmed by material quality specifications. The product of two or more partial design fac-tors can be determined by one test. The design factor K shall not be less than 4,0.
EN 13923:2005 (E) 12 Table 2 — Partial design factors Partial design factor
Min. valueMax. value Effect of inhomogeneities and dispersion A1
1,0 2,0 Effect of vessel liquid and environment A2
1,1 1,8 Effect of design temperature A3
1,0 1,4 Effect of dynamic loading A4
1,0 1,1 Effect of long term behaviour A5
1,25 2,0
7.2.2 The partial design factor for inhomogeneities and dispersion A1 Taking a normal logarithmic distribution the 5 % fracture values shall be regarded as statistically significant for a probability of P = 75 % in an evaluation of at least 5 single values, according to ISO 2602. The partial design factor A1 = 1,0 can be adopted, provided that the 5 % value is employed. When the mean value is taken of at least 10 values, the partial design factor A1 = 1,2 can be adopted. When measured values are used on a non-statistical basis the partial design factor A1 = 2,0 shall be adopted. 7.2.3 The partial design factor for chemical environment A2 The partial design factor A2 for chemical environment shall be derived according to EN 13121-2. 7.2.4 The partial design factor for design temperature A3 The partial design factor A3 for the influence of the design temperature can be obtained from Equation (2). ()()40HDT204,00,13−−+=DTA (2) For service temperatures greater than 40 °C post-curing is required. Post-curing instructions are according to resin manufacturer's recommendations. HDT shall be determined according to EN ISO 75-2:2004 method C or EN ISO 75-3. The partial design factor A3 can also be confirmed experimentally by: measurements on the bending strength, deflection on fracture and/or modulus of elasticity according to EN ISO 14125 at 23 °C and at design temperature; measurements on strain in long term creep tests according to EN ISO 14125 at working stresses, at 23 °C and at design temperature over a minimum of 1 000 h; long-term destructive or non-destructive compression test according to 8.3.3 at 23 °C and at design tem-perature. These tests can be included in the testing of A5. The measured properties shall be extrapolated for the deter-mination of the long-term behaviour according to Annex C. 7.2.5 The partial design factor for dynamic loading A4 The partial design factor A4 for dynamic loading is 1,0 if there is no dynamic loading and 1,1 in case of
dynamic loading. Dynamic loading is defined as more than 10 000 pressure cycles over the service life of the vessel.
EN 13923:2005 (E) 13 7.2.6 The partial design factor for long-term behaviour A5 The partial design factor A5 is 2,0 for long-term behaviour up to 2 × 105 h, which can be reduced if the results from either of the following tests produces a lower value: creep tests according to EN ISO 14125 at working stress, over a minimum of 1 000 h; long-term non-destructive compression test according to 8.3.3 at 23 °C. The measured properties shall be extrapolated for the determination of the long-term behaviour according to Annex C. However, A5 shall never be less than 1,25. 7.2.7 Combination of more than one partial design factor A2 × A3 × A5 can be confirmed by one test according to 8.3.3 when the vessel contents are in contact with the environment throughout the test. The product of these factors shall be calculated in accordance with Annex C. 7.3 Permissible strain The permissible strain at design pressure of lined filament wound vessels shall be specified in accordance with the strain behaviour of the linings and with the medium. Micro-cracks in the supporting laminate are
acceptable because of the protective layer. The maximum permissible strain in the structural laminate,
including as well as bending effects is given in Equation (3): 5maxAlimεε= (3) For media category 3 class IV and sulfuric acid as specified in EN 13121-2, the strain εlim shall not be higher than 0,25 % for all type of protective layers. In case of a chemical resistant layer consisting of a veil layer followed by a layer of sprayed fibres or chopped strand mat with a total mass per unit area of minimum 900 g/m² the limiting strain εlim of the structural laminate shall be according to Table 3. Table 3 — Strain limits for thermosetting protective layer
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