OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.5 Materials – sandwich structures – Page 88
4 Other properties
4.1 Thermal expansion coefficient
4.1.1 Thermal expansion coefficient of the cores in the relevant temperature range shall be measured in the
main material directions.
4.1.2 Stresses due to thermal deformation shall be considered.
4.2 Swelling coefficient for water or other liquids
4.2.1 Swelling coefficient of the plies in the relevant temperature range shall be measured in the main material
directions.
4.2.2 Stresses due to swelling shall be considered.
4.3 Diffusion coefficient
4.3.1 Relevant data shall be obtained as needed for the actual service and exposure of the component. If
relevant, the following material data may be required:
— diffusion rate through the thickness of the core
— diffusion rate along the in-plane axis of the core
— diffusion rate along the interfaces between core and skin.
4.3.2 A special property related to diffusion is vapour transmission. This value is sometime of importance for
sandwich structures.
4.4 Thermal conductivity
4.4.1 Thermal conductivity may be anisotropic for cores. If relevant thermal conductivity shall be obtained.
4.5 Friction coefficient
4.5.1 Core materials are generally not exposed to friction. If they are the same procedure as given in Sec.4 shall
be applied.
4.6 Wear resistance
4.6.1 Core materials are generally not exposed to wear. If they are the same procedure as given in Sec.4 shall
be applied.
5 Influence of the environment on properties
5.1 Introduction
5.1.1 The environment can affects composites. Both adhesives and cores can be affected in different ways due
to their different chemical nature and micro-structure.
5.1.2 Void content and the presence of matrix cracks in the face laminates can indirectly influence the
environmental resistance of the core and adhesive materials. Rapid and excessive water penetration can for
example damage quickly the interface bond between faces and core.
5.1.3 The nature of the core cells, whether closed or opened, influences very significantly the environmental
resistance of the core materials.
5.1.4 The quality of interface bonding between faces and cores, or between cores themselves can also
influence the environmental resistance of the adhesive joints, and thereby the entire sandwich structure.
5.1.5 The local environmental conditions shall be taken into account for the documentation of all properties
under static and fatigue loads, as described above.
5.1.6 Degradation of joining structures shall also be documented, e.g. end enclosures, connections, corners, T-
joints and other fasteners.
5.1.7 Cyclic environmental conditions shall be considered.
5.1.8 It shall be documented that the combined effects of cyclic loads, static load, and the environment are not
worse than the separate effects.
5.1.9 The following conditions are considered:
— temperature
DET NORSKE VERITAS AS