Creep and damage accumulation in orthotropic composites under cyclic loading

Experimental results and theoretical prediction of the response of glassfiber-reinforced polyester under quasi-static, static (creep), and cyclic (fatigue) loading are presented. The nonlinear strain component at static loading and the strain amplitude rate at cyclic off-axis loading of an orthotropic composite are shown to follow the associated flow rule with a single-parameter quadratic potential function. The influence of fatigue damage on deformation is considerable due to the reduction in the elastic modulus of the composite and is apparently negligible with respect to its effect on the parameters of the creep kernel.

Mechanical properties of pultruded glass fiber-reinforced plastic after moistening

Abstract The kinetics of moisture sorption under immersion in water at room and elevated temperatures and flexural characteristics of dry (conditionally initial) and wet (moistened up to saturation level) composite material were investigated on flat specimens of polyester based glass fiber-reinforced plastic, cut from I-beam pultruded profile. It was found that the coefficients of diffusion and swelling are different in three principal axis of the composite. The former have the largest value in fiber axis direction, but the latter – in transverse to fiber axis direction out of plane of the layers. The observed difference in kinetics of mass gain and change of volume strain for the specimens…

Long-term moisture absorption and durability of FRP pultruded rebars

Abstract Up to 15-years long moisture diffusion into carbon, glass, and aramid fiber reinforced plastic (FRP) rebars is studied. To eliminate uncertainties in identification of the radial and axial diffusivities, a successive methodology for determination of the diffusion coefficients is proposed. The concept of apparent diffusivity taking into account anisotropy and edge effects is extended to cylindrical samples. The ratio of the axial and radial diffusivities is the lowest for carbon (3) and the highest for glass (81) FRP rebars. Durability performance of the rebars is estimated by monitoring their interlaminar shear strength (ILSS). Long-term exposure of FRP rebars in a humid environmen…

Modeling of creep for multiwall carbon nanotube/epoxy nanocomposite

The effect of multiwall carbon nanotubes (MWCNTs) on creep of epoxy matrix was evaluated on the basis of short-term creep-recovery tests performed at different stresses and temperatures. Six different compositions of MWCNT and bisphenol A epoxy resin (0-3.8 wt % of MWCNTs) were investigated. Slight reduction of creep compliance, strain rate, and residual strain were revealed experimentally for nanocomposite comparing to the neat resin. The development of viscoelastic strain for creep stage was described by the use of time-temperature-strain superposition principle with the parameters obtained from the approximation of recovery stage using modified Schapery model. The model accounted for the…

Relationship between the residual and total strain from creep‐recovery tests of polypropylene/multiwall carbon nanotube composites

Creep of polymer concrete in the nonlinear region

Two polyester-based polymer concretes with various volume content of diabase as an extender and aggregate are tested in creep under compression at different stress levels. The phenomenological and structural approaches are both used to analyze the experimental data. Common features of changes in the instantaneous and creep compliances are clarified, and a phenomenological creep model which accounts for the changes in the instantaneous compliance and in the retardation spectrum depending on the stress level is developed. It is shown that the model can be used to describe the experimental results of stress relaxation and creep under repeated loading. Modeling of the composite structure and su…