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Glossary
Deformation Under Load.
Measure of the ability of rigid plastics to withstand per-
manent deformation and the ability of nonrigid plastics
to return to original shape after deformation. Standard
test methods for determining both types of deformation
under load are given in ASTM D-621. For rigid plastics,
deformation (which can be flow or flow and shrinkage)
is reported as % change in height of specimen after 24
hours under a specified load. For nonrigid plastics, re-
sults are reported as % change in height after 3 hours un-
der load and recovery in the 1-1/2 hour period following
removal of the load. Recovery is % increase in height
calculated on basis of original height.
Delamination Strength.
Measure of the node-to-node bond strength of honey-
comb core materials. It is equal to the tensile load ap-
plied to a honeycomb panel at fracture divided by its
width times its thickness (ASTM C-363).
Dry Strength.
Strength of an adhesive joint determined immediately af-
ter drying or after a period of conditioning in a specified
atmosphere. (ASTM D-2475).
Ductility.
Extent to which a material can sustain plastic deforma-
tion without rupture. Elongation and reduction of area
are common indices of ductility.
Dynamic Creep.
Creep that occurs under fluctuating load or temperature.
B-9
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