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The effect of pressure and temperature on time‐dependent changes in graphite/epoxy composites below the glass transition
Author(s) -
Mijović Jovan,
Liang R. C.
Publication year - 1984
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760240107
Subject(s) - materials science , epoxy , glass transition , composite material , graphite , enthalpy , volume (thermodynamics) , thermodynamics , polymer , physics
Effects of pressure and temperature on time‐dependent changes in physical/mechanical properties of graphite/epoxy composites were investigated. Samples were cut from the eight‐ply‐thick laminates of commercially used composites, post‐cured, and then quenched to environments of various temperature and pressure. Time‐dependent changes in their properties were analyzed by thermal and thermomechanical (dynamic mechanical) measurements. An increase in the glass‐transition temperature was found to occur as a function of time. The rate of this process was enhanced by an increase in temperature and/or a decrease in pressure. An explanation was offered in terms of types and mechanisms of molecular events that occur in the glassy state. Time dependent decrease in free volume (and enthalpy) takes place but is not the sole mechanism responsible for the observed increase in T g . After a certain period of time (which depends on T and P of the environment), additional crosslinking appears to take place.