Impact fatigue damage of coated glass fibre reinforced polymer laminate

Abstract

Impact fatigue caused by rain droplets, also called rain erosion, is a severe problem for wind turbine blades and aircraft. In this work, an assessment of impact fatigue on a glass fibre reinforced polymer laminate with a gelcoat is presented and the damage mechanisms are investigated. A single point impact fatigue tester is developed to generate impact fatigue damage and SN data. Rubber balls are repeatedly impacted on a single location of the coated laminate. Each impact induces transient stresses in the coated laminate. After repeated impacts, these stresses generate cracks, leading to the removal of the coating and damage to the laminate. High-resolution digital imaging is used to determine the incubation time until the onset of coating damage, and generate an SN curve. An acoustic emission sensor placed at the back of the laminate monitors changes in acoustic response as damage develops in the coated laminate. The subsurface cracks are studied and mapped by 3D X-ray computed tomography. A finite element method model of the impact shows the impact stresses in the coating and the laminate. The stresses seen in the model are compared to cracks found by 3D tomography. The damage is also evaluated by ultrasonic scanning.

Micromechanisms of leading edge erosion of wind turbine blades: X‐ray tomography analysis and computational studies

“…For the analysis of stress wave distribution in coated laminates, a finite element (FE) model was developed in the commercial FE code ABAQUS, on the basis of the approaches described in Fraisse et al A water droplet (diameter of 3 mm and velocity of 100 m/s) hitting multilayered coated laminate was specified in the Lagrangian domain, where the material was not fixed to the mesh but flew through it. The coated laminate was modeled using the commonly used Eulerian domain.…”

“…The coated laminate was modeled using the commonly used Eulerian domain. The model was symmetric . The simulations were carried out with Abaqus Explicit.…”

“…Becuase of the symmetry conditions, one quarter of the model was considered. The behavior of water was defined via linear Hugoniot equation of state, with parameters 1.45e + 06 and 0 . The microstructures of the coatings (as observed in section ) were included in the models.…”

Toolbox for optimizing anti‐erosion protective coatings of wind turbine blades: Overview of mechanisms and technical solutions

“…Depending on frequency and volume content of particles, the attenuation coefficient is of the order of 100 to 300 1/m for low frequency ranges (2)(3)(4)(5)(6)(7)(8). 79 For the case of epoxy filled with glass spheres, the losses of energy (effective total attenuation) is proportional to the frequency with the coefficient 0.456 e-6/2π sec/cm.…”

“…The problem of rain erosion of large moving objects became more important with broad development of wind energy, especially, large wind turbines and offshore turbines . Wind turbines with the sizes of up to 120 m each blade are expected to serve over 20 years.…”