3 research outputs found
Development of nanoengineered coatings for leading edge protection of wind turbine blades
This research is focused on developing rain erosion resistant coatings for leading edge of
the wind turbine blades. One of the critical problems of wind turbine blades is erosion of its
leading edge. Leading edge erosion (LEE) will degrade the aerodynamic performance of the
wind turbines by increasing the drag force and decreasing the lift force. Past studies showed
that the annual energy production (AEP) of the wind turbine can be reduced by up to 25% due
to LEE. Hence, applying an erosion resistant coating to the wind turbine blades is necessary.
Elastomeric polyurethane (PU) has been used for LEE protection. The approach of this research
is to use PU and enhance its the mechanical properties by introducing carbon nanoparticles
(CNPs) multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelets (GNP) and also
increase the hydrophobicity of the PU by introducing silica-based sol-gel (SG).
Initially the effect of the environmental temperature on mechanical properties of the pure PU
was studied by performing tensile tests at different temperatures and strain rates. It was found
that increasing the temperature decreases the tensile properties of the pure PU and increasing
the strain rate will increase these properties.
For optimising mixing parameters of CNPs in PU, PU was modified by CNPs at three different
mixing speeds and three different mixing durations. Tensile tests were performed on these
nanocomposites, and the optimum mixing duration (18 minutes) and speed (8000 rpm) where
nanocomposite materials showed the highest mechanical performance were established.
The optimum weight percentage of nanoparticles loading was also required. The PU was
modified at different CNPs loading and the tensile tests were performed on pure and modified
PUs. The results of the tensile tests showed that PU with 0.5wt% of MWCNTs and PU with
0.5wt% of GNP-COOH loading resulted in the highest amount of Young’s modulus, UTS,
elongation at break and modulus of toughness. Other CNPs such as GNP-NH3 and combined
GNP-COOH/CNT and GNP-NH3/CNT were also investigated. The results showed that
modifying PU with GNP-COOH at 0.5wt% loading gives the best tensile properties. Finally,
the hydrophobicity of the coating was improved by adding silica-based sol-gel to the GNP
modified PU. The water contact angle (CA) experiments showed that modifying PU with GNP
and SG increased the CA of neat PU from 56 degree to 110 degree for PU+GNP+SG while the
free surface energy reduced from 114.6 mJ/m2
to 50 mJ/m2
.
The cyclic compression tests were carried out and the results revealed that the maximum stress
at maximum strain of 0.5 for PU is 107.9 MPa, for PU + GNP is 77.4 MPa and for PU + GNP
viii
+ SG is 71.5 MPa. This indicates PU + GNP + SG experiences the least stresses during cyclic
compressive loading. Tearing test results showed that the PU + GNP nanocomposite has the
highest tearing strength and PU + GNP + SG has the highest elongation at break. The PU +
GNP + SG nanocomposite has much higher value for Young’s modulus (95%), tensile strength
(115%), modulus of toughness (124%) and elongation at break (102%) relative to the neat PU
at room temperature. In addition, the tearing energy for both modified PU nanocomposites was
higher than the neat PU (137% increase for PU + GNP and 148% increase for PU + GNP +
SG).
In addition to the mechanical tests, water absorption test was carried out for a period of six
months to analyse the amount of the water that can be absorbed by developed materials and the
effect of absorbed water on the tensile properties of the coating materials were identified.
Experimental results showed that after six months, the weight of the pure PU, PU+GNP and
PU+GNP+SG increased by 4%, 3.7% and 3.6%, respectively. The results showed that
absorbing water by PU decreases the tensile properties of the material.
Microstructural analysis of the developed PU coatings by FTIR, field emission scanning
electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDX) were carried
out and the detailed results are presented in this thesis.
Finally the developed coatings were tested for anti-erosion performance using the single point
impact fatigue testing (SPIFT) technique. It is demonstrated that graphene / silica reinforced
PU coating can provide better erosion protection with substantial longer time before material
loss than non-reinforced PU
Nanoengineered graphene-reinforced coating for leading edge protection of wind turbine blades
Possibilities of the development of new anti-erosion coatings for wind turbine blade surface protection on the basis of nanoengineered polymers are explored. Coatings with graphene and hybrid nanoreinforcements are tested for their anti-erosion performance, using the single point impact fatigue testing (SPIFT) methodology. It is demonstrated that graphene and hybrid (graphene/silica) reinforced polymer coatings can provide better erosion protection with lifetimes up to 13 times longer than non-reinforced polyurethanes. Thermal effects and energy dissipation during the repeated soft impacts on the blade surface are discussed
Graphene/sol–gel modified polyurethane coating for wind turbine blade leading edge protection : properties and performance
The development of two novel elastomeric erosion resistant coatings for the protection of wind turbine blades is presented. The coatings are prepared by modifying polyurethane (PU) with (i) hydroxyl functionalised graphene nanoparticles (f-GNP) and (ii) f-GNP and a hydrophobic silica-based sol–gel (SG). Tensile, monotonic and cyclic compression and tearing tests have been conducted on the neat PU and the two newly developed elastomeric PU nanocomposites (PU + GNP and PU + GNP + SG) to allow their properties to be compared. The test results showed that the mechanical properties of PU and the modified PUs have strong dependency on temperature, strain rate and nanoparticles loading and addition of GNP and SG to PU improved the mechanical properties. Compared to PU, Young’s modulus and modulus of toughness of PU + GNP + SG increased 95% and 124%, respectively. The PU + GNP nanocomposite displayed the highest tearing strength and the PU + GNP + SG nanocomposite showed the highest elongation at break. An investigation of the microstructures of the modified PUs by FTIR, field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDX) are discussed. Hydrophobicity of the PU and developed PU nanocomposites are reported by measuring their water droplet contact angles and their free surface energies