The problem of mechanical design, performance prediction (e.g., flap-wise/edge-wise bending stiffness, fatigue-controlled life, the extent of bending-to-torsion coupling), and material selection for a prototypical 1 MW horizontal-axis wind turbine (HAWT) blade is investigated using various computer-aided engineering tools. For example, a computer program was developed which can automatically generate both a geometrical model and a full finite-element input deck for a given single HAWT-blade with a given airfoil shape, size, and the type and position of the interior load-bearing longitudinal beam/shear-webs. In addition, composite-material laminate lay-up can be specified and varied in order to obtain a best combination of the blade aerodynamic efficiency and longevity. A simple procedure for HAWT-blade material selection is also developed which attempts to identify the optimal material candidates for a given set of functional requirements, longevity and low weight.

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A multi-disciplinary design-optimization procedure has been introduced and used for the development of cost-effective glass-fiber reinforced epoxy-matrix composite 5 MW horizontal-axis wind-turbine (HAWT) blades. The turbine-blade cost-effectiveness has been defined using the cost of energy (CoE), i.e., a ratio of the three-blade HAWT rotor development/fabrication cost and the associated annual energy production. To assess the annual energy production as a function of the blade design and operating conditions, an aerodynamics-based computational analysis had to be employed. As far as the turbine blade cost is concerned, it is assessed for a given aerodynamic design by separately computing the blade mass and the associated blade-mass/size-dependent production cost. For each aerodynamic design analyzed, a structural finite element-based and a post-processing life-cycle assessment analyses were employed in order to determine a minimal blade mass which ensures that the functional requirements pertaining to the quasi-static strength of the blade, fatigue-controlled blade durability and blade stiffness are satisfied. To determine the turbineblade production cost (for the currently prevailing fabrication process, the wet lay-up) available data regarding the industry manufacturing experience were combined with the attendant blade mass, surface area, and the duration of the assumed production run. The work clearly revealed the challenges associated with simultaneously satisfying the strength, durability and stiffness requirements while maintaining a high level of wind-energy capture efficiency and a lower production cost.

In this study, electromagnetic shielding properties of needle-punched nonwoven fabrics were investigated. The paper evaluates and compares the electromagnetic shielding of needle-punched nonwoven fabrics produced from stainless steel/polyester and normal polyester fibers. Stainless steel/polyester fiber and normal polyester fiber were blended at specified ratios in the experimental study. Webs were produced from the fibers with the carding machine and then bonded with the needle-punching machines. The thickness and electromagnetic shielding properties of the needle-punched fabrics were tested. An electromagnetic shielding effectiveness (EMSE) device was used for measuring the electromagnetic shielding. The experimental study indicated that as the conductive stainless steel fiber ratio in nonwoven fabrics increases, the EMSE also increases at low, medium and high frequencies. Satisfactory electromagnetic shielding values were obtained at wide bandwidth, i.e. 1200–3000 MHz. The highest EMSE values of the needle-punched nonwoven fabric with 25% conductive steel fiber were, respectively, 6 dB at 0–300 MHz low frequency, 12 dB at 300–1200 MHz medium frequency and 18 dB at 1200–3000 MHz high frequency. It was found that 90% of electromagnetic waves were shielded by nonwoven fabric at high frequencies, 85% at medium frequencies and 80% at low frequencies.

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