OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.5 Materials – sandwich structures – Page 94
Table 5-10 Requirements for individual material to be part of representative data
(Continued)
Constituent core material(s):
Requirements to group measurements from different sandwich
cores
Process parameters to be given with exposure time:
Laminator (company)
Processing method
Processing temperature
Processing pressure
Process atmosphere (e.g. vacuum)
Curing temperature
Post curing (temperature and time)
Density of sandwich structures
Not relevant
Same for all tests*
Same for all tests*
Same for all tests*
Same for all tests*
Same for all tests*
Same for all tests*
Same for all tests*
Conditioning parameters:
Temperature
Water content of the core (wet, dry)
Chemical environment
Loading rate
Same for all tests*
Same for all tests*
Same for all tests*
Same for all tests*
Number of specimens:
* a wider range may be chosen if data are the minimum of a wide variety of products.
8.6 Qualification against representative data
8.6.1 A product may be qualified against representative data if certain requirements are met for cores and
adhesives.
8.6.2 Similarity is described here for core materials and core adhesives. Skin laminates shall be treated like
laminates described in Sec.4 [8]. For testing of core properties the skin properties are usually not relevant.
8.6.3 Cores may be considered to be similar, if:
— the core is of the same generic type, e.g. cross-linked PVC, PUR, end-grained balsa, etc.
— the cell structure is the same
— the raw materials to produce the core are the same
— manufacturer and trade name may be different
σ ∧
— the shear strength xc core linear and compressive characteristic strength (
similarity requirements given in [8.7]
1t
fibre and 1c
fibre) fulfil the
— the shear and compressive modulus is within 5% of the reference core.
8.6.4 Cores may be considered to be similar for a certain property, if:
Reported individually for all properties
— the core is of the same generic type, e.g. cross-linked PVC, PUR, end-grained balsa, etc.
— the cell structure is similar
— the raw materials to produce the core are the same
— manufacturer and trade name may be different
— the shear strength xc core linear and compressive characteristic strength ( 1t
fibre and 1c
fibre) fulfil the
similarity requirements given in [8.7] after corrections for the density change have been made according to
[6.3]
— the shear and compressive modulus is within 5% of the reference core after corrections for the density
change have been made according to [6.3].
σ ∧
8.6.5 A core adhesive can be considered to be similar, if the adhesive is of the same generic type, e.g.
vinylester, epoxy, and if its strain to failure is not less than the reference adhesive.
8.6.6 If the above basic similarity requirements are met, individual static sandwich structure properties shall
be qualified as described in Table 5-11. Some properties can be based directly on represented data or an
equation to modify them is given. Other properties shall be confirmed by experiment (see [8.7]-[8.9]).
8.6.7 Instead of confirming all material parameters individually component testing may be used to qualify an
analysis, as described in Sec.4 [8.11].
ε ∧
ε ∧
ε ∧
ε ∧
DET NORSKE VERITAS AS