Fatigue Model for Fiber-Reinforced Polymeric Composites for Offshore Applications.
Fatigue Model for Fiber-Reinforced Polymeric Composites
for Offshore Applications.
Nguyen, T.; Tang, H. C.; Chuang, T. J.; Chin, J. W.; Wu,
H. F.; Lesko, J.
NIST TN 1434; 43 p. September 2000.
Available from: Government Printing Office, Washington,
Order number: SN003-003-03657-9
fatigue (materials); offshore platforms; composite
materials; stress (mechanics); tensile strength; civil
A model based on cumulative damage has been developed
for predicting the fatigue life of fiber-reinforced
polymeric composites used in offshore environments. The
model incorporates applied stress, stress amplitude,
loading frequency, residual tensile modulus, and
material constants as parameters. The model is verified
with experimental data from a glass fiber/vinyl ester
composite fatigued under different environmental
conditions. Specimens are subjected to tension-tension
fatigue at four levels of applied maximum tensile stress
at two different frequencies while exposed to air, fresh
water, and sea water at 30 deg C. Both the residual
mechanical properties at specified loading cycles and
the number of cycles at which the specimens fail are
measured. For the material used in this study, the loss
in mechanical properties (residual tensile strength and
modulus) in salt water is approximately the same as that
in fresh water, and the fatigue life of the composite in
these aqueous environments is shorter than that in air.
The S-N curves for specimens subjected to the three
environments have approximately the same slope,
suggesting that the failure mechanism does not change
with these environments. Furthermore, specimens that are
fatigued at a lower frequency failed at a lower number
of cycles than those tested at a higher frequency.
Numerical analysis is performed using the fatigue
experimental data to determine the material constants of
the composite. The model agrees well with the
experimental data, and it can be used to predict the
fatigue life of polymeric composites subjected to an
applied load in different environments or the residual
tensile modulus after a number of loading cycles.