Java Comp 150
Owner’s Manual
Filaments or fibres are used as they exhibit superior mechanical properties than large expanses of the
material. The two main reasons are that fine filaments can be bent around a much smaller radius than
larger pieces. (Consider a fine filament of fibre glass and a sheet of glass.) The other reason is that
carefully extruded filaments contain many fewer imperfections per unit length than a larger object. In
materials such a glass the imperfections seriously reduce the strength.
Another property of composite materials is their
Anisotropy.
That is they exhibit different mechanical
properties such as strength and stiffness along different axes. In CFRP the majority of the strength is in the
direction of the fibres. This is different to metal alloys which are generally described as
Orthotropic
which
means they exhibit the same mechanical properties in all directions. CFRP can be made
Quasi-orthotropic
(similar to orthotropic) by running fibres in all directions. There is sometimes little reason to replace a
metal with a quasi-orthotropic composite.
The salient point is that carbon fibre is not like metal and must be treated differently. It is much less
resistant to high temperatures than metals but more corrosion resistant. However the main area of concern
is the ability to detect damage in carbon fibre: a sharp blow to a metal tube is likely to result in an easily
detectable dent. The same blow to a carbon fibre tube may leave a barely visible mark while significantly
reducing its strength.
As a result of this commercial composite aircraft parts are designed to have sufficient strength with Barely
Visible Impact Damage (BVID) and thus 'perfect' parts have enormous safety margins. Of course Avian
cross tube spars are designed to the same criteria. However a small dent in a carbon fibre cross tube should
be considered as much more serious damage than a similar sized dent in an aluminium cross tube. Damage
such as this should be examined professionally, by Avian, before flying.
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Summary of Contents for JAVA COMP 150 Dacron
Page 27: ...Java Comp 150 Owner s Manual Appendix ASSEMBLY DRAWINGS NOSE ASSEMBLY 27...
Page 28: ...Java Comp 150 Owner s Manual 28...
Page 29: ...Java Comp 150 Owner s Manual CROSS TUBE LEADING EDGE JUNCTION 29...
Page 30: ...Java Comp 150 Owner s Manual 30...
Page 32: ...Java Comp 150 Owner s Manual VARIABLE BILLOW VB OR VARIABLE GEOMETRY VG 32...
Page 33: ...Java Comp 150 Owner s Manual Appendix CHECKING WASHOUT GLIDER MINIMUM REQUIREMENTS 33...