# Comparative Study on Vibration Characteristics of Biaxial Carbon/Glass Hybrid Wind Turbine Blades
## 3 Blade Material Preparation and Performance Analysis
### Material Tensile Performance Testing  
Four laminated plates were cut using a CNC cutting machine to prepare corresponding tensile specimens. Five specimens were prepared for each type along the latitude direction. The schematic diagram of the specimens is shown in Figure 3. The sample size requirements are shown in Table 1.  
The spline size parameters are shown in Table 1.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Symbol** & **Title** & **Size/mm** \\ \hline \(L\) & Specim length & 250 \\ \(b\) & Specim width & 15 \\ \(h\) & Specim thickness & 30 \\ \(L_{0}\) & Test length & 80 \\ \(L_{1}\) & The length of the piece & 50 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Ensile specimen size parameters.  
Figure 3: Schematic diagram of tensile specimen.  
Figure 2: Flow Chart of Composite Material Sample Preparation.  
When formulating the experimental design scheme, the calibration pattern of spray paint is utilized to ascertain the dimensions of the tensile test data through DIC speckle deformation analysis. Following the completion of sample production, each type of sample undergoes calibration using the spray painting technique, with the calibration process being finalized by allowing the spray paint to dry. The laboratory is presently equipped with an MTS landmark fatigue testing machine, which is capable of fulfilling the mechanical testing requirements and delivering precise and replicable standard tensile test outcomes. A depiction of the tensile testing procedure for the sample is presented in Figure 4.  
Place the sample vertically on the ground and clamp it with a movement rate of 2 mm/min. Use the WS-3811 digital strain gauge from Shanghai Precision Instruments Co., Ltd. to obtain the load value and displacement variation curve. Figure 5 shows the quasistatic tensile test diagram.  
The tensile stress-strain curve of the specimens with different carbon/glass ratios were obtained by breaking the specimens, shown in Figure 6. The performance table of carbon/glass hybrid blade specimens is shown in Table 2.  
As shown in Figure 6, the carbon/glass hybrid ratio has a significant impact on the tensile properties of the sample. As the ratio of carbon/glass hybrid layers increases, the tensile stress of the sample increases and the strain decreases. Compared with the glass fiber sample, the sample with a carbon/glass hybrid ratio of 2:6 (cggg) showed a 4.10% increase in stress and a 1.31% decrease in strain. The sample with a carbon/glass hybrid ratio of 4:4 (ccgg) showed a 37.27% increase in stress and a 18.36% decrease in strain. The stress of the specimen (cccg) with a ratio of 6:2 increases by 47.32%, while the strain decreases by 28.36%. This is due to the higher breaking strength and lower elongation at the break of carbon fibers.  
Figure 4: Process of Sample Tensile Testing.  
According to the analysis in the above table, when the carbon/glass hybrid ratio of the sample is 4:4, compared to the hybrid ratio of 2:6, the material properties are significantly  
Figure 5: Quasistatic tensile test diagram.  
Figure 6: Stress–Strain Curves of Different Carbon/Glass Hybrid Fiber Layer Ratios.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Name**} & **Carbon/Glass** & \multirow{2}{*}{**E/(GPa)**} & \multirow{2}{*}{**G/(GPa)**} & \multirow{2}{*}{**P/(g\(\cdot\)cm\({}^{-3}\))**} \\  & **Hybrid Ratio** & & & \\ \hline (gggg)s & 0.8 & 4.72 & 1.86 & 1.79 \\ (cggg)s & 2:6 & 5.15 & 2.02 & 1.78 \\ (ccgg)s & 4:4 & 8.15 & 3.17 & 1.73 \\ (cccg)s & 6:2 & 9.67 & 3.69 & 1.73 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Table of Tensile Performance Parameters.  
improved, with a relative increase of 34.17% in equivalent strength and 58.27% in equivalent modulus. From this, it can be seen that the carbon to glass ratio shows the greatest trend in performance improvement between 2:6 and 4:4.