Question

QuestioN1 You are workingon a team that is building a lightweight, remote-controlled aircraft with the goal of lifting as much payload as possible. Your team has selected a design that will use a rectangular wing with a constant cross-section in the form of a high-lift airfoil. You are responsible for the initial sizing of the load carrying spar that runs the entire span of the wing. In flight, the spar acts much like a loaded cantilevered beam, as shown in Fig. 1. An objective of the design is that it be as light as possible, while also being cheap to manufacture. A requirement of the wing spar is that it carry a load equivalent to a tip loading of 445 N with a maximum deflection of 5% of the spar length L. Due to supply options material choices are limited to either aluminum or carbon fibre reinforced composites, both of which are available as circular rods, hollow tubes, and rectangular bars. For aircraft stability reasons, the spar should be centred (front to back) on the quarter-chord location of the airfoil as shown in Fig. 2. The spar must be contained within the outline of the airfoil as shown in Fig. 2 for different valid spar designs. Using suitable engineering analysis, select the material and cross-sectional shape and dimensions of the spar to satisfy the above design problem. Material properties as reported by the supplier are listed below in Table 1. Note that only basic engineering analysis is required, however there are severalfactors to consider. There exists many possible solutions to this problem. You should attempt to thoroughly analyze this problem and produce a recommended best solution that satisfies the above design problem. 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 Eppler 420 0.05 0.05 Center of Spar 0.15 0.2 0.25 0.3 0.35 0.45 -0.5 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 04 0.45 05 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 Figure 2: Airfoil coordinates normalized to a chord length of one. Inset: isometric view of wing Table 1. Supplier-provided material properties Material Al 6061 CF composite Density (g/cm3 2.70 1.60 Young's modulus (GPa) 69 134 Yield strength (MPa 250 600 Cost USD/kg) 2.53 P-445 N Spar Spar 1.80 m 0.400 m Figure 1: Wing spar geometry

Answer 1

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