OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.4 Materials - laminates – Page 58
Wear rate proportional
to (pv)
Log p
Figure 4-4
Wear rate (plotted against log pv)
Log v
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4.6.8 Wear properties usually degrade at elevated temperatures. The effects of ambient temperature and of
frictional heating should be considered.
4.6.9 The presence of water between the two surfaces in contact usually has a lubricating effect, i.e. the wear
properties of the wear system are better than those of the same system without presence of water.
4.6.10 Frictional coefficients and wear rates of materials are strongly influenced by the roughness of the
counter-face against which they are sliding. In the steady state wear condition abrasive wear can become the
dominant mechanism if the surface of the wearing material has been modified during previous passages.
Typically, the wear mechanism changes from adhesion in the range of very smooth surfaces to abrasion for
rough surfaces, leading to an increase of the wear rate.
4.6.11 The presence of fibres usually improves the wear resistance of a polymer matrix. The fibres are exposed
at the sliding surface and support part of the applied loads. Moreover, the fibres smooth the surface of the
counter-face to reduce the localised stresses at the asperity contacts.
Guidance note:
Carbon fibres are usually superior to glass fibres in reducing the wear rate and the frictional coefficient. Especially at
high sliding speeds and high loads, they clearly improve the wear properties of the base polymer. For practical
application of composites where friction becomes an important problem ,the use of a hybrid material (glass and carbon
fibres) can be recommended.
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4.6.12 The orientation of the fibres in a polymer material with a given fibre content has also an influence on
its wear properties:
— for unidirectional laminates, the lowest wear rates are often obtained when the fibres are orientated
perpendicular (normal) to the sliding surface
— when the fibres are orientated parallel to the sliding surface, the differences between anti-parallel and
parallel orientation are less clear.
4.6.13 The presence of fillers usually helps to reduce wear. However, the wear reducing action of fillers is
dependent on factors such as shape and size, as well as the composition of the filler material.
4.6.14 Internal lubricant such as PTFE or silicone can be used to improve the wear resistance of a material.
The two materials combine at the wear surface and form a high lubricate film, which acts in addition as a
protecting layer for the fibres.
5 Influence of the environment on properties
5.1 Introduction
5.1.1 The environment can effect composites. Properties change usually gradually with time and long
exposure times (a year and longer) are needed before properties change significantly.
5.1.2 Fibres and matrix are effected in different ways due to their different chemical nature.
5.1.3 The fibre matrix interface can have an important influence on the environmental resistance. The interface
properties are influenced by the type of fibre, the sizing, the matrix, and the processing conditions.
5.1.4 Void content and the presence of matrix cracks can also influence the environmental resistance.
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