OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.5 Materials – sandwich structures – Page 93
8.2.3 Long-term test results shall be reported as mean regression curve, standard deviation with respect to time
or cycles, number of test specimen, range of test time or number of cycles. Test points shall be spread out
relatively evenly over the logarithmic test period. The characteristic values of long-term tests shall be
calculated as described in Sec.4 [3.11].
8.3 Selection of material qualification method
8.3.1 The test results shall apply to the core and adhesive used in the component to be designed and built. Test
results are only applicable if the test core and adhesive and the sandwich structures are similar enough that the
test results are valid or conservative for the actual component.
8.3.2 If a core material is the same as an already tested material no further testing is required. The same core
material means:
— same basic material type, e.g. balsa, honeycomb, PVC foam core
— same core manufacturer, same trade name
— no change with respect to cell structure, processing method, raw materials used.
8.3.3 If a core material is similar to an already tested material qualification against a representative material
may be carried out. Requirements for similarity are given in [8.6], requirements for representative data are
given in [8.5].
8.3.4 Direct measurements as described in [8.4] shall be carried out if [8.3.2] or [8.3.3] cannot be applied.
8.3.5 Any change of adhesive requires re-qualification of the properties related to the adhesive performance
as described in [8.6].
8.4 Direct measurement
8.4.1 The various properties of a composite may be measured directly for a particular material. Data will be
valid for that particular material that was tested. The material shall be characterised as required in section [1.2].
8.4.2 The test methods described in App.D should be preferred.
8.5 Representative data
8.5.1 If a sufficient number of direct measurements is available, data may be used to establish a set of
representative data for a material property. To be considered representative, data should be based on at least 15
measurements per property. Other materials can be compared against the representative data as described in
[8.6].
8.5.2 Representative data are most useful if they can be used for a fairly wide range of materials. This will also
allow to pool data of different properties that were obtained from slightly different materials. Requirements for
to the individual materials that can be put into one group of representative data are given in Table 5-10.
Table 5-10 Requirements for individual material to be part of representative data
Constituent core material(s):
Generic core type (e.g. foam, honeycomb, balsa etc.)
Core trade name
Type of core (e.g. linear foam)
Type/ characteristics of microstructure
Core manufacturer
Batch number
Glass transition temperature
Constituent adhesive material(s):
Generic adhesive type (e.g. epoxy, polyester)
Specific adhesive type trade name
Specific adhesive type batch number
Catalyst
Accelerator
Fillers (trade name and batch number)
Additives (trade name and batch number)
Requirements to group measurements from different sandwich
cores
Same for all tests
Same for all tests
Same for all tests
Same for all tests
Same for all tests
Not relevant
Lowest from all tests
Same for all tests
Same trade name*
Not relevant
Same trade name*
Same trade name*
Same trade name*
Same trade name*
DET NORSKE VERITAS AS