TITLE:
Relationship between the Initial Fracture Stress and Fatigue Limit—Simple Prediction Method of Tensile Fatigue Limit of Composite
AUTHORS:
Y. Imai, K. Nishitani, G. Fortin, A. Ohtani, H. Hamada
KEYWORDS:
Initial Fracture, Fatigue Limit, Acoustic Emission Testing, Tensile Testing, Bending Testing
JOURNAL NAME:
Open Journal of Composite Materials,
Vol.9 No.4,
September
24,
2019
ABSTRACT: This article presents an experimental study that clarifies the
relationship between the initial fracture stress and fatigue limit of glass
fiber reinforced unsaturated polyester resin specimens with a laminated
structure taken from a pultruded square pipe. Quasi-static bending and tension
tests are performed with acoustic emission (AE) measurements to identifying the
occurrence of initial fracture during testing. AE and observation results have
clarified the occurrence of initial fracture was detected by maximum acoustic
energy values and corresponding fiber breakage in the unidirectional (UD)
bundles. Moreover, the ratio of initial fracture stress to ultimate strength is
32% in bending and 26% in tension, when comparing stress and strains on the tension
side of the UD layer. These values are in good agreement with each other and
with the measured tensile fatigue limit when the cyclic stress is at 25% of the
tensile strength. Initial fracture stress obtained by static tests is close values
to the fatigue limit which will greatly contribute to the prediction of the
fatigue limit.