OS-C501

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Offshore Standard DNV-OS-C501, November 2013 Sec.4 Materials - laminates – Page 68 Table 4-11 Qualification against representative data (Continued) Mechanical parameter Low safety class Normal safety class High safety In-plane orthotropic elastic constants ν 13 ν 23 ε ∧ 3t ε ∧ 3c Poisson’s ratio normal to the fibre plane, including the fibre direction, when tensioning in the fibre direction. Poisson’s ratio normal to the fibre plane, including the direction normal to the fibres, when tensioning in the plane normal to the fibres. Tensioning strain at break, normal to the fibre plane. Compression strain at break, normal to the fibre plane. class rep × 1 rep × 1 confirm if critical for design rep × 1 rep × 1 confirm if critical for design rep × 0.9 or ε ∧ = × 0.9 2t rep × 0.9 or ε ∧ = 2c × 0.9 confirm if critical for design confirm if critical for design confirm if critical for design confirm if critical for design Tensioning strain at break normal to rep × 0.9 or ε ∧ 13 the fibre plane when tensioning in the fibre direction. = ε ∧ 12 × 0.9 confirm if critical for design confirm if critical for design ε ∧ 23 Tensioning strain at break normal to rep × 0.9 or the fibre plane when tensioning in the fibre plane, normal to the fibre direction. = ε ∧ 12 × 0.9 Tensioning stress at break normal to rep or the fibre plane. calculate σ ∧ 3t σ ∧ 3c 13 σ ∧ 23 σ ∧ Compression stress at break normal to the fibre plane. Stress at break normal to the fibre plane when tensioning in the fibre direction. Stress at break normal to the fibre plan, including the direction normal to the fibres, when tensioning normal to the fibre plane. rep or calculate rep or calculate rep or calculate confirm if critical for design calculate calculate calculate calculate confirm if critical for design calculate calculate calculate calculate Fracture Toughness Critical length In-plane rep × 0.8 confirm confirm G 1c Critical strain energy release rate in the fibre direction. rep × 0.8 confirm confirm G 2c Critical strain energy release rate in rep × 0.8 confirm confirm the fibre plane, normal to the fibre direction. Long Term Properties (see [8.6.15] and [8.6.16]) Creep/Stress relaxation rep confirm if critical confirm for design Stress rupture rep confirm if critical confirm for design Static strength reduction under permanent load rep rep confirm if critical for design Change of modulus under cyclic fatigue Cycles to failure fibre dominated Cycles to failure matrix dominated Fibre dominated static strength reduction under fatigue load rep rep confirm if critical for design rep confirm if critical confirm for design rep confirm if critical confirm for design rep rep confirm if critical for design DET NORSKE VERITAS AS
Offshore Standard DNV-OS-C501, November 2013 Sec.4 Materials - laminates – Page 69 Table 4-11 Qualification against representative data (Continued) In-plane orthotropic elastic constants Matrix dominated static rep strength reduction under fatigue load 8.6.12 The entry “rep” in Table 4-11 means that representative data may be used without testing. In some cases the representative data shall be multiplied by a factor as indicated in Table 4-11. 8.6.13 Confirm if critical for design means that the value or procedure of the lower safety class may be used for strength or strain to failure if the material safety factor γ m can be multiplied by 2 for this property in all relevant failure criteria. Otherwise the property should be confirmed by testing. 8.6.14 Through thickness elastic properties should only be confirmed by testing if they influence the calculation of a critical strength or strain as defined in [8.6.13]. Otherwise the representative values my be used. 8.6.15 Long term test data of fibre dominated properties do not have to be confirmed if the laminate has identical fibres, matrix and sizing compared to a laminate for which long term test data exist and the static similarity tests in [8.6.4] are fulfilled. The requirement to the same matrix and sizing can be waived if environmental attack on the fibres can be excluded. 8.6.16 Long term test data of matrix dominated properties do not have to be confirmed if the laminate has identical fibres, matrix and sizing compared to a laminate for which long term test data exist and the static similarity tests in [8.6.4] are fulfilled. 8.6.17 The procedure of the higher safety class may always be used to obtain better values than can be obtained by using the procedure of the lower safety class. 8.6.18 If any of the confirmation tests show that the material is not similar to the representative material, all properties shall be re-qualified. 8.6.19 A full experimental determination of a property may always be used as an alternative to using representative data or confirmation testing. 8.7 Confirmation testing for static data Mechanical parameter Low safety class Normal safety class High safety 8.7.1 If a material is similar to a material for which representative data exist (as described above) two methods can be used to demonstrate that the similar material is at least as good as the typical material. One is a simplified method, the other is similar data hypothesis testing. 8.7.2 At least three measurements of the property in question shall be made in all cases. It is recommended to test five or more specimens. 8.7.3 For the simplified method the following requirements shall be fulfilled: confirm if critical for design — the standard deviation estimated from at least three measurements shall not be larger than the standard deviation of the corresponding typical data — at least 50% of the measured values shall be larger than the mean of the typical data — at least 84% of the measured values shall be larger than the mean - 1 standard deviation of the typical data — at least 97.7% of the measured values shall be larger than the mean - 2 standard deviations of the typical data. 8.7.4 If a material is similar to a material for which representative data exist (as described above) the hypothesis testing can be used to determine whether test data can be considered to belong to the same population. 8.7.5 Let µ 0 denote the mean value of the typical data, and let σ 0 denote the standard deviation of the typical data. Calculate: n( x − µ 0 ) T = ˆ σ where x is the mean value of the n measurements of the material to be checked for similarity. class confirm if critical for design DET NORSKE VERITAS AS
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