OS-C501

Offshore Standard DNV-OS-C501, November 2013
App.D Test methods for sandwich materials – Page 223
D.4.2 Fracture toughness of the interface
D.4.2.1 The test method covers the determination of the fracture toughness parameters occurring in an
interfacial crack.
Guidance note:
At the cracked interface face/core of a transversely loaded sandwich structure, the crack tip is subjected to both mode-
I and mode-II stress fields.
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D.4.2.2 For mode-I fracture toughness measurement, two test specimen can be used: the double-cantilever test
specimen (DCB), or its modified version fitted with hinges.
D.4.2.3 The interlaminar fracture toughness for isotropic materials is given by:
K
2
Ic
EG
Ic
P
=
( d P)
,
c ∂
1− ν
D.4.2.4 For mode-I fracture toughness measurement, the 'Cracked-Sandwich-Beam' (CSB) test specimen can
be used.
D.4.2.5 Delamination strength of honeycomb type core material can be determined by carrying out the test
ASTM C 363-57.
D.4.3 Other tests
2
D.4.3.1 Sandwich peel tests are used to determine the peel resistance of adhesive bonds between facings and
cores. Several tests methods exist; the climbing drum tests methods, ASTM D 1781; DCB-type peel test; peel
tests using air pressure; the recommended test methods is ASTM D 1781-93.
D.5 Tests for other properties
D.5.1 Coefficient of thermal expansion
D.5.1.1 The test covers the determination of the coefficient of linear thermal expansion of core materials.
D.5.1.2 The recommended test methods are ASTM D 696-91 (within the range of +30 and -30ºC), ISO
4897:1985.
D.5.2 Water absorption tests
D.5.2.1 The test covers the determination of the relative rate of water absorption when immersed in a highly
humid environment.
D.5.2.2 The recommended test method is ASTM D 2842-6. Other test methods are available such as ASTM
C 272-91, IDO 2896:1987.
D.5.3 Diffusion and vapour transmission
G
=
2w
D.5.3.1 The test aims to determine the permeability of water vapour through permeable or semi-permeable
materials.
D.5.3.2 The water vapour permeability (WVP) is calculated as:
WVT =
∆W
tA
where - ∆W - is the weight change, - t - is time and - A - the test area.
∂a
D.5.3.3 The recommended test method is SS 02 15 82. Other tests are available: ASTM E 96-94, ISO
1663:1981, ISO/DIS 1663.
D.5.4 Tests for thermal conductivity measurements
Ic
D.5.4.1 The recommended test method is ASTM C 177-85. Other test methods can be used such as ASTM C
168-90, ASTM C 236-89, ASTM C 1045-90. The test covers the determination of the steady-state heat flux
through flat specimens.
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