Mvsln. Kowsika et Pr. Mantena, OPTIMAL PULTRUSION PROCESS CONDITIONS FOR IMPROVING THE DYNAMIC PROPERTIES OF GRAPHITE-EPOXY COMPOSITE BEAMS, Materials evaluation, 54(3), 1996, pp. 386-392
The manufacturing process variables significantly influence the mechan
ical properties of pultruded composites. In this study, a statistical
central composite design (CCD) test pattern has been used to manufactu
re unidirectional graphite-epoxy pultruded composite beams under caref
ully controlled process conditions. The influences of significant pult
rusion process variables and their effects/interactions on the dynamic
mechanical properties were investigated. The pultruded specimens were
subjected to free vibration decay tests to determine nondestructively
the dynamic flexural modulus and loss factor (a measure of internal d
amping). Mathematical models were derived based on the observed values
of the dynamic properties using regression analysis procedures. These
models were used to determine the optimal pultrusion process conditio
ns for improving the dynamic mechanical properties of the finished pro
duct. A theoretical model postulating varying distribution of fiber co
ntent through the thickness of the pultruded composite is also present
ed. Static flexural tests and microscopic evaluation were employed to
validate the assumption that a thin distinct layer of matrix material
is formed on the outer surface of these pultruded products.