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## Assessment of Research Needs for Wind Turbine Rotor Materials Technology (1991) Commission on Engineering and Technical Systems (CETS)

### Citation Manager

. "3 MATERIALS PROPERTIES AND LIFE PREDICTION." Assessment of Research Needs for Wind Turbine Rotor Materials Technology. Washington, DC: The National Academies Press, 1991.

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Assessment of Research Needs for Wind Turbine Rotor Materials Technology

TABLE 3-2 Typical Properties of Unidirectional Composites

 E-Glass/Resin KEVLAR Resin Graphite/Resin S-Glass/Resin Fiber Direction Modulus, GPa 44.8 75.8 145 56 Strength tension, MPa 1124 1241 1517 1980 Strength compression, MPa 896 276 2068 626 Coefficient of thermal expansion, microstrain/K 8.8 -4.0 -0.45 5.5 Transverse Direction Modulus, GPa 11.0 5.52 10.3 11.4 Strength tension, MPa 31 14 48 31 Strength compression, MPa 138 55 138 138 Coefficient of thermal expansion, microstrain/K 22.1 57.6 25.2 23.3 Shear (Inplane) Modulus, GPa 4.14 2.41 5.52 4.48 Strength, MPa 71.7 34.5 82.7 71.7 Poisson Ratio Axial-Transverse 0.27 0.34 0.30 0.27 Thickness Direction Modulus, GPa 11.0 5.5 10.3 11.4 Poisson ratio 0.44 0.38 0.55 0.44

To further illustrate the cost differences based on fibers, consider a hybrid composite with a carbon/glass volume ratio vc/g. The ratio of the cost of the hybrid composite to an all-glass composite to provide the same structural stiffness is given by

The parameters in Equation (1) are defined as follows: \$, price per unit mass; s, specific gravity; E, Young's modulus; g, glass; and c, carbon. On the other hand, the weight ratio, defined as the weight of the hybrid composite divided by that of the all-glass composite, is given by

E-glass fiber costs around \$2/lb; a high-strength carbon fiber costs about \$30/lb. Thus, an all-carbon fiber composite costs 3.5 times more than an all-glass fiber composite to provide the same structural stiffness at a weight savings of 76 percent. When a 50/50 glass/carbon hybrid composite is used, however, the calculated cost ratio is reduced to 2.9 with a weight savings of 58 percent.

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 FRONT MATTER (R1-R10) EXECUTIVE SUMMARY (1-4) 1 INTRODUCTION (5-24) 2 STRUCTURAL LOADING CHARACTERISTICS (25-34) 3 MATERIALS PROPERTIES AND LIFE PREDICTION (35-66) 4 WIND TURBINE ROTOR DESIGN ISSUES (67-80) 5 MANUFACTURING PROCESSES FOR ROTOR BLADES (81-90) 6 ACTIVE CONTROL IN WIND TURBINES (91-100) 7 CONCLUSIONS AND RECOMMENDATIONS (101-104) APPENDIX A: STATEMENT OF TASK (105-106) APPENDIX B: COMMITTEE MEETINGS AND ACTIVITIES (107-108)