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SUMMARYNumerical implementation of quasibrittle cohesive cracking is still an open issue, 30 years after the introduction of the fictitious crack by Hillerborg. The paper first briefly presents the existing trends and underpins the basic problems of the various procedures, especially the necessity (to avoid crack locking) of tracking algorithms to enforce crack path continuity. As an alternative, the paper describes a recent method based on very simple ingredients: strong discontinuity kinematics, constant stress tetrahedral, crack equilibrium solved at element level, damage-like cohesive crack with central forces, and limited local crack adaptability that is able, as shown by the examples, to describe the cohesive crack growth with adequate accuracy while keeping the formulation strictly local (element level only, no neighbours information required).

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This paper presents an experimental and statistical study of the fatigue behavior of unidirectional glass fiber-reinforced epoxy composite rods manufactured using pultrusion technique and modified with nanoparticles of alumina (Al2O3) and silica (SiO2) at four different weight fractions (0.5, 1.0, 2.0 and 3.0 wt.%). Tensile test was performed to investigate the influence of nanoparticles. Addition of alumina nanoparticles up to 3 wt.% increases the tensile strength by 54.76% over the pure glass fiber-reinforced epoxy specimen. For silica nanoparticles, there is an increase in the tensile strength of 31.29% for the content of 0.5 wt.% over the pure glass fiber-reinforced epoxy specimen. As the silica nanoparticles’ content increases over 0.5 wt.%, there is a decrease in the tensile strength. Rotating bending fatigue tests have been conducted at five different stress levels. Fatigue life of glass fiber-reinforced epoxy composite rods modified with alumina nanoparticles increases as the content of the nanoparticles increases. The effect of adding silica nanoparticles on the fatigue life of glass fiber-reinforced epoxy composite rods is relatively insignificant with a small improvement in the content of 0.5 wt.% silica above the pure glass fiber-reinforced epoxy specimens. Two-parameter Weibull distribution function was used to statistically analyze the fatigue life data.

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