TY - JOUR
T1 - A viscoelastic-plastic analysis of an aramid composite beam in flexure
T2 - rate of testing effects, stress relaxation and creep
AU - Fischer, S.
AU - Roman, I.
PY - 1986/12
Y1 - 1986/12
N2 - Using an elastic-plastic analysis it has previously been shown that the compressive yield strength (microbuckling mode) dominates the flexural properties of aramid composite beams. It determines the actual stress and strain distributions, which can be derived from the apparent (nominal elastic) stress as well as from the apparent fracture strength. In this work we have studied the time dependence of flexural properties for post-compressive yielding deformation of aramid composites. The previous analysis was adapted into a viscoelastic-plastic analysis by realizing that the compressive yield strength of aramid composites has logarithmic time and rate dependences. The analysis predicts and the experiments showed that (a) the apparent fracture stress increases linearly with increase in the logarithm of the rate of testing, (b) in stress relaxation tests the stress relaxation increases linearly with increase in the logarithm of the time, and the rate increases linearly with increase in the maximum stress level reached and (c) in creep tests the logarithm of the creep rate increases with increase in the time, and the logarithm of the lifetime is linear with the apparent creep stress for lifetimes of up to 3 days. The results of this work support the assumption that compressive yielding is time dependent and is a major contributor to the time effects of an aramid composite beam in flexure for post-yield deformation.
AB - Using an elastic-plastic analysis it has previously been shown that the compressive yield strength (microbuckling mode) dominates the flexural properties of aramid composite beams. It determines the actual stress and strain distributions, which can be derived from the apparent (nominal elastic) stress as well as from the apparent fracture strength. In this work we have studied the time dependence of flexural properties for post-compressive yielding deformation of aramid composites. The previous analysis was adapted into a viscoelastic-plastic analysis by realizing that the compressive yield strength of aramid composites has logarithmic time and rate dependences. The analysis predicts and the experiments showed that (a) the apparent fracture stress increases linearly with increase in the logarithm of the rate of testing, (b) in stress relaxation tests the stress relaxation increases linearly with increase in the logarithm of the time, and the rate increases linearly with increase in the maximum stress level reached and (c) in creep tests the logarithm of the creep rate increases with increase in the time, and the logarithm of the lifetime is linear with the apparent creep stress for lifetimes of up to 3 days. The results of this work support the assumption that compressive yielding is time dependent and is a major contributor to the time effects of an aramid composite beam in flexure for post-yield deformation.
UR - http://www.scopus.com/inward/record.url?scp=0022866998&partnerID=8YFLogxK
U2 - 10.1016/0025-5416(86)90226-0
DO - 10.1016/0025-5416(86)90226-0
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AN - SCOPUS:0022866998
SN - 0025-5416
VL - 84
SP - 97
EP - 103
JO - Materials Science and Engineering
JF - Materials Science and Engineering
IS - C
ER -