Jh. Lee et Jh. Vogel, AN INVESTIGATION OF NECKING INSTABILITY IN FIBER-REINFORCED POLYPROPYLENE, Journal of engineering materials and technology, 118(1), 1996, pp. 80-87
Thermoplastic composite materials hold considerable promise for increa
sed use in low cost high volume applications because of the potential
for processing by solid phase forming. Unfortunately, because of the w
ide variety of such materials, inherent variability in properties, and
complex temperature and strain rate dependence, large strain behavior
of these materials has not been well characterized Of particular impo
rtance is failure during processing due to localized necking instabili
ty and it is this phenomenon that is the primary focus of this study.
Large strain behavior under uniaxial tension is characterized over a r
ange of temperatures and strain rates, and a simple linear viscoelasti
c model is Pt to the observed data, The strain rare and temperature de
pendence is then used to predict limiting tensile strains based on Mar
ciniak imperfection theory. Excellent correlation was obtained between
theory and experiment and the results are summarized in maps of formi
ng limit as a function of temperature and strain rate, These results s
uggest that excellent solid phase formability may be obtained for the
materials tested under properly chosen conditions.