OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.11 Fabrication – Page 170
3.5 Resin
3.5.1 Two or more component resins shall be carefully mixed according to manufacturers instructions, this is
essential for a good cure.
3.5.2 The curing system shall be chosen in a way to prevent exothermic overheating.
3.5.3 Changing accelerators or other ingredients that control the speed of the cure are only permitted if they
have no effect on the mechanical properties. The resin supplier shall confirm this. In addition, tensile tests
according to Sec.4 [8.6.7] shall confirm no change in strength and stiffness for components of normal and high
safety class.
3.5.4 Barcol's hardness tests or other means should be used to check the quality of the cure.
3.5.5 The viscosity of the resin and or the gel time should be measured for all processes where the flow
properties of the resin are important.
3.5.6 It is recommended to take a sample from each batch of resin used in components of normal or high safety
class. The sample of resin without fibres should be cured separately. A tensile or bending test should be used
to confirm that properties are within acceptable tolerances.
3.6 Producing laminates and sandwich panels
3.6.1 Procedures to confirm the lay-up of fabrics shall be established. A log shall be kept for components of
normal or high safety class. The accuracy of the lay-ups shall be verified independently during production for
high safety class components. Whether the verification shall be done by the manufacturer himself, by the
customer, or by a third party should be decided by the project.
3.6.2 The accuracy of fibre orientations shall be specified for high safety class components.
3.6.3 Fibres shall be well aligned showing no local distortions or kinks.
3.6.4 Minimum and maximum overlap lengths of adjacent fabrics shall be specified. The effect of overlaps
may be similar to damage in the laminate and shall be evaluated as described in Sec.4 [1.7].
3.6.5 The tolerances for gaps between cores shall be defined.
3.6.6 The surfaces of cores shall have smooth transitions across the gaps. This is especially critical if cores are
tapered.
3.6.7 Procedures shall be established to ensure a good bond between skins and cores for all geometrical shapes
in the component. The quality of the interfacial bond shall be documented for all relevant geometry, e.g.,
convex and concave surfaces.
3.6.8 Any gaps between cores shall be filled with the specified resin or adhesives, unless it was specified that
cores shall not be filled and core properties were measured on cores with unfilled gaps, see Sec.5 [6.2].
3.6.9 Absorption of resin by the core shall be considered with respect to weight of the total structure and the
amount of resin needed to obtain the desired fibre volume fraction in the laminates.
3.6.10 The curing temperature and pressure shall not effect the properties of the core.
3.6.11 The temperature of all materials and the mould should be the same during the lay-up, unless the process
specifically requires other conditions.
3.7 Producing joints
3.7.1 The same requirements as for laminates and sandwich plates in [3.5] apply.
3.7.2 Overlap lengths shall be clearly specified and tolerances shall be given.
3.7.3 Surface preparations of adhesive or laminated joints shall be clearly specified and shall be the same as
for the specimens that were tested to qualify the joint.
3.7.4 The application of adhesives shall follow well described procedures. The procedures shall be exactly the
same as for the specimens that were tested to qualify the joint.
3.7.5 Surface preparation of adhesive or laminated joints and the application of adhesives shall be verified
independently during production for normal and high safety class components. Whether the verification shall
be done by the manufacturer himself, by the customer, or by a third party should be decided by the project.
3.7.6 The alignment of components and tolerances shall be specified.
DET NORSKE VERITAS AS