D. Barpanda et Pr. Mantena, EFFECT OF HYBRIDIZATION ON THE CREEP AND STRESS-RELAXATION CHARACTERISTICS OF PULTRUDED COMPOSITES, Journal of reinforced plastics and composites, 17(3), 1998, pp. 234-249
Pultrusion manufacturing process is a well established technique for t
he cost-effective production of high-modulus and lightweight composite
materials having constant cross-sectional profiles. The pultruded com
posites are widely used as structural members viz., beams, trusses and
stiffeners, owing to the presence of high proportion of axial fibers
necessary to sustain large tractive forces. These structural members a
re subjected to a combination of static and dynamic loading conditions
at wide temperature ranges and over longer periods. Since polymeric c
omposites exhibit viscoelastic behavior, the effectiveness of these ma
terials as structural members must be thoroughly evaluated to ensure l
ong-term stability. In previous research, the dynamic performance char
acteristics of pultruded glass-graphite/epoxy hybrids were evaluated a
t room temperature. The effects of temperature, frequency, post-curing
, along with the type and placement of fibers on the dynamic flexural
properties of glass/epoxy and hybrid glass-graphite/epoxy were also in
vestigated. This paper focuses on the evaluation of creep and stress r
elaxation performance characteristics of pultruded glass-graphite/epox
y hybrid composites. Dynamic mechanical analysis technique was adopted
for the accelerated creep and stress relaxation testing. Time-tempera
ture superposition principle, which greatly reduced the experimental t
ime, was effectively utilized for predicting the creep and stress rela
xation properties of the hybrid composites. Results indicate that the
type and amount of fibers as well as their lay-up sequence plays a sig
nificant role in determining the flow and load bearing characteristics
.