OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.7 Joints and interfaces – Page 134
3.4.4 A large sandwich plate can be well described by core shear properties obtained from large test specimens.
In the neighbourhood of joints local variations in properties of the core may become critical.
4 Interfaces
4.1 General
4.1.1 If loads shall be transferred across an interface all aspects related to joints shall be considered.
4.1.2 If interfaces only touch each other friction and wear should be considered according to Sec.6 [13].
4.1.3 Fluids may accumulate between interfaces. They may accumulate in voids or debonded areas and/or
break the bond of the interface. The effect of such fluids should be analysed. Possible rapid decompression of
gases should be considered Sec.6 [12].
4.1.4 Liners that do not carry any structural loads shall have a high enough strain to failure or yield that they
can follow all possible movements of the interface. Yielding of liners should be avoided, since yielding can
cause local thinning or introduce permanent stresses after yield. If yielding cannot be avoided it shall be
analysed carefully. The effect of local yielding on the surrounding structure shall also be considered.
4.1.5 If one substrate may crack (e.g. have matrix cracks), but the other shall not crack, it shall be shown that
cracks cannot propagate from one substrate across the interface into the other substrate. Possible debonding of
the interface due to the high stresses at the crack tip should also be considered.
4.1.6 It is recommended to demonstrate by experiments that cracks cannot propagate across the interface from
one substrate to the other. It should be shown that by stretching or bending both substrates and their interface
that no cracks forms in the one substrate even if the other substrate has the maximum expected crack density.
Guidance note:
This is a typical situation for pressure vessels with liners. The load bearing laminate may have some matrix cracks,
but the liner shall not crack to keep the vessel tight. Local debonding of the liner may be acceptable if the liner will
not collapse due to its own weight, negative internal pressure or other effects.
---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---
Guidance note:
A weak bond between the substrates is beneficial to prevent crack growth across the interface. However, it means that
debonding may happen easily.
---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---
DET NORSKE VERITAS AS