OS-C501

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Offshore Standard DNV-OS-C501, November 2013 Sec.4 Materials - laminates – Page 42 1.7 Properties of laminates with damage 1.7.1 In some cases a structure is expected to contain some damage, e.g. impact damage, delaminations, cracks etc. If this is the case, the laminate can be modelled with this damage as described in Sec.9 and Sec.6. Alternatively, the laminate can be described with properties based on a laminate with damage. 1.7.2 Strength properties of a laminate with damage shall be measured on laminates that contain the maximum expected damage. It shall be carefully evaluated if the damage can be representative in small test coupons. If there is any doubt about testing of laminates with damage a conservative approach shall be chosen, that gives lower than expected strength values. 1.7.3 Elastic constants like stiffness and Poisson's ratio shall be measured on damaged and undamaged laminates. It shall be noticed that modelling a structure with elastic properties based on a damaged laminate may give wrong stress distributions (See Sec.9). 2 Static properties 2.1 General 2.1.1 All material properties shall be given with full traceability of materials and conditions. Test results are only valid if the information given in Table 4-1 is available. Tests shall be reported as mean, standard deviation, and number of tests. 2.1.2 For many applications the static properties after exposure to long term loads and environments are more important than the static properties of a new material. This fact should be kept in mind when selecting materials and developing a test programme. Long term properties are described in the following sections. 2.2 Static properties 2.2.1 The complete list of orthotropic ply data is shown in Table 4-2. Recommended test methods to obtain the properties are given in App.C. Fibre and matrix dominated properties are identified in the column “characteristic” as F and M respectively. 2.2.2 Static properties are generally assumed to be identical to quasi-static properties, measured at a testing rate of about 1% per minute. If loading rates in the component differ from this rate, tests should be made at the relevant rates or corrections of the data should be considered. Table 4-2 Static properties In-plane orthotropic elastic constants Mechanical parameter Unit Char. Reference App.C for measurement method E 1 fibre UD-ply Modulus of elasticity in main fibre direction [GPa] F [C.2.1] E 2 matrix UD-ply Modulus of elasticity transverse to main fibre direction [GPa] M [C.2.1] E 1 linear cross-ply Modulus of elasticity in 0° fibre direction in the liner [GPa] M, F [C.2.1] range E 2 linear cross-ply Modulus of elasticity normal to the 0° fibre direction [GPa] M, F [C.2.1] in the liner range E 1 non-linear cross-ply Secant modulus of elasticity in 0° fibre direction at [GPa] F [C.2.1] the failure point E 2 non-linear cross-ply Secant modulus of elasticity normal to the 0 fibre [GPa] F [C.2.1] direction at the failure point G 12 linear In plane shear modulus in the liner range [GPa] M [C.2.3] G 12 non-linear In plane secant shear modulus at the failure point [GPa] M [C.2.3] ν 12 Ply major Poisson’s ratio F, M [C.2.1] ν 21 Ply minor Poisson’s ratio F, M [C.2.1] In-plain Strain to Fail fibre ε ∧ Tensile strain at break for the fibres F [C.2.1] 1t Fibre ε ∧ Compressive strain at break for the fibres F, M [C.2.2] 1c matrix Tensile strain at break for the matrix in direction M [C.2.1] ε ∧ 2t normal to the fibre direction, in the fibre plane. matrix Compressive strain at break for the matrix in M [C.2.2] ε ∧ 2c direction normal to the fibres. matrix ε ∧ Shear strain at failure in ply plane M [C.2.3] 12 DET NORSKE VERITAS AS
Offshore Standard DNV-OS-C501, November 2013 Sec.4 Materials - laminates – Page 43 Table 4-2 Static properties (Continued) In-plane orthotropic Mechanical parameter Unit Char. Reference App.C elastic constants for measurement method In-plane Strength σ ∧ 1t σ ∧ 1c 2t σ ∧ σ ∧ 2c 12 Fibre Tensile stress at break in the fibre direction N/mm 2 (MPa) Fibre Compressive stress at break in fibre direction N/mm 2 (MPa) matrix Tension stress at break normal to the fibre direction. N/mm 2 2.2.3 If only one sub index is given in the Table 4-2, it is identical to two indices of the same kind, e.g. = . 2.2.4 The index fibre indicates ply properties in fibre direction. Failure stresses and strains with the index fibre describe ply failure in fibre direction. It does not mean that a single fibre has failed, usually a number of fibres fail before the ply breaks. 2.2.5 The index matrix indicates matrix dominated ply properties perpendicular to the fibre direction. Failure stresses and strains with the index matrix describe matrix cracking inside the ply. This is usually the initiation of matrix cracks. F [C.2.1] F, M [C.2.2] M [C.2.1] (MPa) matrix Compressive stress at break normal to the fibre N/mm 2 direction (MPa) M [C.2.2] shear Shear stress in ply plane at failure. N/mm 2 M [C.2.3] (MPa) Through -thickness E 3 Modulus of elasticity normal to the fibre plane. GPa M [C.2.4] or [C.2.5] σ ∧ G 13 G 23 ν 13 ν 23 3t ε ∧ c ε ∧ 3 ε ∧ 13 23 ε ∧ σ ∧ 3t σ ∧ 3c σ ∧ 13 23 σ ∧ σ ∧ 11 σ ∧ 1 Shear modulus normal to the fibre plane, including the fibre direction GPa M [C.2.6] Shear modulus normal to the fibre plane, including GPa M [C.2.6] the direction normal to the fibres. Poisson’s ratio normal to the fibre plane, including M [C.2.1] or [C.2.6] the fibre direction, when tensioning in the fibre direction. Poisson’s ratio normal to the fibre plane, including M [C.2.1] or [C.2.6] the direction normal to the fibres. Tensile strain at break normal to the fibre plane. M [C.2.4] Compression strain at break normal to the fibre plane. Shear strain at failure normal to the fibre plane, including the fibre direction. Shear strain at failure normal to the fibre plane, normal to the fibre direction. Tension stress at break normal to the fibre plane. N/mm 2 (MPa) Compression stress at break normal to the fibre plane. Shear stress at failure normal to the fibre plane, including the fibre direction. Shear strain at failure normal to the fibre plane, normal to the fibre direction. N/mm 2 (MPa) N/mm 2 (MPa) N/mm 2 (MPa) M M M M M M M [C.2.5] [C.2.6] [C.2.6] [C.2.4] [C.2.5] [C.2.6] [C.2.6] Fracture toughness Critical length Maximum tolerable In-plane length of crack. mm F/ M [C.2.7] G1c Critical strain energy release rate. (Mode I). N/m M [C.2.8] G2c Critical strain energy release rate in the fibre plane N/m M [C.2.8] (Mode II). G3c Not used DET NORSKE VERITAS AS
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OS-C501

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