OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.11 Fabrication – Page 168
SECTION 11 FABRICATION
1 Introduction
1.1 Objective
1.1.1 The objective of this section is to provide guidelines to ensure that the structure is built as planned and
that the material properties are of consistent quality with the same properties as used in the design analysis. It
is not the intention here to give advise on how to operate particular processing equipment.
1.2 Quality system
1.2.1 This standard does not specify how requirements are controlled, it specifies what should be controlled.
1.2.2 A quality system, like ISO 9001, shall be in place to specify how production activities are controlled. All
requirements given in this section shall be addressed in the quality system for components with normal and
high safety class.
2 Link of process parameters to production machine parameters
2.1 Introduction
2.1.1 Composite laminate and sandwich structures are normally produced as the component is built. This is a
special situation compared to other materials like metals that are purchased as a finished material and
subsequently assembled, joined, and maybe modified.
2.1.2 The material properties depend not only on the raw materials but also on the specific way they are laid up.
2.1.3 The main quality principle when building composite structures is to ensure that the laminates and
sandwich structures are built with a consistent quality.
2.2 Process parameters
2.2.1 The following process parameters shall be controlled as a minimum for laminates, as described in Sec.4
[6]:
— temperate and pressure over time in production and post-cure
— void content
— fibre content (volume fraction) / good local wet-out
— fibre orientation
— fibre tension
— number of layers and thickness.
2.2.2 For sandwich structures the requirements for laminates apply ([2.2.1]). In addition a good bond between
skins and core shall be ensured at all places, see also Sec.5 [6]. If sections of core materials are joined by
adhesives good filling of all joints shall be ensured at all places.
2.3 Production machine parameters
2.3.1 Production machine parameters are defined here in a wide sense as all physical parameters that may have
an influence on the process, since no specific production process is addressed in this standard.
Guidance note:
A production machine parameter can be an electrical current that produces a certain temperature in a curing chamber
in a pultrusion process; it can be rolling pressure when compacting reinforcements in a hand lay-up process.
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2.3.2 All production machine parameters shall be identified that may influence the process parameters in
B200.
2.3.3 Ideally a link between the dependence of processing parameters on machine parameters should be
established. If such a link cannot be established, the parameters should be kept constant or within well defined
tolerances.
2.3.4 Material properties should be established as a function of the process parameters and it shall be shown
that the design values (mean and standard deviation) can be achieved under all conditions. Alternatively,
material properties shall be measured and used in the design for the worst possible variation of machine
parameters.
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