OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.5 Materials – sandwich structures – Page 91
5.7.2 Test data should be obtained of the combined effect of environments on the material properties if
relevant. The worst relevant combination of environments should be used for testing.
6 Influence of process parameters and core density
6.1 Core production
6.1.1 Core materials are generally manufactured in a well-controlled process. This standard does not address
manufacturing methods of core materials. It is assumed that the measured and reported core properties can be
reproduced and guaranteed by the core manufacturer.
6.1.2 In some cases the core properties may be influenced by the joining methods used to join the skins or core
sections. This aspect is described in [6.2].
6.2 Sandwich production
6.2.1 The skins are usually laminated onto the core or glued onto the core. Sections of the core may also be
joined with adhesives or some fillers.
6.2.2 The joints may influence the properties of the core either by modifying the core material itself or by
becoming part of the core system. Core properties shall be measured and evaluated with the presence of such
joints.
6.2.3 Changes in process parameters effect joints in a similar way as described for the matrix in a laminate in
[6].
6.3 Influence of core density
6.3.1 For core materials that are available in different densities, all mechanical properties shall be assumed to
depend on the density unless evidence exists that suggests otherwise.
6.3.2 All relationships between properties and density shall be confirmed by experimental evidence for the
particular core type. Data may be interpolated, but should not be extrapolated to densities outside the measured
range.
6.3.3 If a relationship can be established between core density and certain core properties qualification of
material properties may be simplified as described in section [8.6].
7 Properties under fire
7.1 Introduction
7.1.1 The performance of composites in a fire is a complex process, because the various constituent materials
respond differently to a fire.
7.1.2 The requirements under fire conditions can usually be found in the fire codes for a particular application.
7.1.3 Fire codes may implicitly assume that the structure is built of steel or metal. The relevance of a fire code
to composite materials shall be checked carefully.
7.1.4 Since most composites are flammable and temperature sensitive most applications use protective
measures to reduce the impact of fire. In this case the fire performance of the complete system, composite
structure with fire protection shall be evaluated.
7.1.5 Some aspects of fire performance can be modelled, but some experimental testing shall always be done
to demonstrate fire performance.
Guidance note:
Sandwich panels with no internal cavities, such as wood and foam core materials, will not allow any stack effect or
neither help the transportation of combustion products. Conversely, sandwich structures with internal cavities will
enhance these phenomenon.
7.2 Fire reaction
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7.2.1 Fire reaction describes the response of a composite to fire in terms of flammability, flame spread, smoke
development and emission of toxic gases. All these aspects shall be documented if relevant.
7.2.2 Special additives or fillers are often added to composites to improve fire reaction.
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