Counter-bore showing bolt head recessed.
Counter boring through the
sandwich structure skin results
in in-plane stresses being
reacted by the weak foam core.
This counter-bore configuration
is un-acceptable if the bolt
carries any load. A insert will not
resolve the un-acceptable
stress state.
sandwich structure skin results
in in-plane stresses being
reacted by the weak foam core.
This counter-bore configuration
is un-acceptable if the bolt
carries any load. A insert will not
resolve the un-acceptable
stress state.
A recess for the bolt head can be molded into
the Composite Sandwich Structure. The
recess geometry substitutes for the
counter-bore. The connectivity of the skins is
preserved. An insert is shown to prevent
foam compression.
the Composite Sandwich Structure. The
recess geometry substitutes for the
counter-bore. The connectivity of the skins is
preserved. An insert is shown to prevent
foam compression.
An INSERT BLOCK is molded
within the composite sandwich
structure. The counter-bore is
machined in the structure after
manufacture. The insert block
preserves the connectivity between
skins.
within the composite sandwich
structure. The counter-bore is
machined in the structure after
manufacture. The insert block
preserves the connectivity between
skins.
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Attachment of tooling to skinned sandwich structures for some applications requires the bolt head to be recessed into
the structure. The normal custom and practice is to counter-bore the structure sufficiently deep to accept the bolt
head either in line or below the structure surface. The counter-bore width is usually sufficient to accept the bolt head
with clearance for a torque wrench.
the structure. The normal custom and practice is to counter-bore the structure sufficiently deep to accept the bolt
head either in line or below the structure surface. The counter-bore width is usually sufficient to accept the bolt head
with clearance for a torque wrench.
Counter-bores in Composite Sandwich Structures can be accommodated by means of sandwich structure geometry,
and insert block geometry. All methods provide connectivity between top and bottom skins resulting in the skins
transferring in-plane stresses.
and insert block geometry. All methods provide connectivity between top and bottom skins resulting in the skins
transferring in-plane stresses.
UN-ACCEPTABLE COUNTER-BORE COMPOSITE SANDWICH STRUCTURE CONFIGURATIONS
COUNTER-BORE from SANDWICH STRUCTURE GEOMETRY
COUNTER-BORE within INSERT BLOCK
