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understand the reasons behind the choice of any structure you
must be aware of the different types of loading they have to
withstand. |
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There
are four main direct loads that any material in a structure
has to withstand:
Tension Compression
Shear Flexure
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Tension
The figure opposite shows a tensile
load applied to a composite. The response of a composite
to tensile loads is very dependent on the tensile stiffness
and strength properties of the reinforcement fibres, since
these are far higher than the resin system on its own. |
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Compression
The figure opposite shows a composite
under a compressive load. Here, the adhesive and stiffness
properties of the resin system are crucial, as it is the
role of the resin to maintain the fibres as straight columns
and to prevent them from buckling. |
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Shear
The figure opposite shows a composite
experiencing a shear load. This load is trying to slide
adjacent layers of fibres over each other. Under shear
loads the resin plays the major role, transferring the
stresses across the composite. For the composite to perform
well under shear loads the resin element must not only
exhibit good mechanical properties but must also have
high adhesion to the reinforcement fibre. The interlaminar
shear strength (ILSS) of a composite is often used to
indicate this property in a multi-layer composite ('laminate'). |
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Flexure
Flexural loads are really a combination
of tensile, compression and shear loads. When loaded as
shown, the upper face is put into compression, the lower
face into tension and the central portion of the laminate
experiences shear. |
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