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This is assignment for Material and Structures course. To cover following points, Prof. Aparijita Singh assigned this task at Andhra University to engineering students: Floor, Design, Structural, Engineer, Cross-section, Sizing, Instrumentation, Airplane, Fuselage, Station, Recommendations, Material, Skins, Stringers
Typology: Exercises
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You and your team of colleagues are employed as structural engineers at Small-Planes-R-Us, Inc. The board of directors has committed the company to producing a new small two-seater airplane. Your engineering manager is responsible for the fuselage design and specifically assigned your team to work on the aft fuselage between the wing and the tail. She has asked you to submit a preliminary design for this section of the fuselage in about three weeks. The aerodynamics group has decided to go with a circular cross-section and it is divided into two regions by a "floor" to attach some instrumentation as specified by the avionics group. The preliminary sizing work has defined the diameter of the cross-section near the wing region (aft fuselage station 0) to be 180 cm, and at the tail connection point (aft fuselage station 250) the diameter is 90 cm. The length of this section is 250 cm.
FIGURE 1 Side view of aft fuselage.
250 cm
180 cm (^) 90 cm
Fall, 2002
You have been asked, specifically, to make recommendations for the areas and materials to be used for the stringers and the thicknesses of the floor and skin of the fuselage. This is to help your engineering manager prepare for a "Design-Build Team" meeting where representatives from the various aspects of the engineering divisions as well as manufacturing and marketing representatives will confer to better define the design.
The preliminary sizing and configuration work has defined a cross-section for the aft fuselage. This configuration consists of skins connecting four stringers: one at the top of the fuselage, one at the bottom, and one on each side of the floor at the floor level. In a discussion with your group, your manager has provided you with the following information as well as the accompanying figures:
FIGURE 2 Cross-section dimensions.
180 cm
Floor
Floor
90 cm
Fall, 2002
Preliminary material information
The following material properties have been furnished by the materials department:
Material E (^) L [GPa] νLT σL allowable^ [ MPa] τLallowable^ [ MPa] ρ [ g/cm 3 ]
Gr/Ep laminate 110 0.4 500 ---- 1.
Aluminum 70 0.3 350 180 2.
Preliminary load information
The loads on the aft fuselage are primarily due to the lift loads on the horizontal stabilizer and the rudder/vertical stabilizer. (The fuselage is not pressurized.) The loads can be considered to act at a point. There are three types of loads at the tail location (station 250) which may be considered to act separately for the purposes of preliminary design:
Fall, 2002
Preliminary design criteria
A preliminary assessment of usage has been conducted based on historical data as well as a survey of past and potential customers. The following design criteria for the aft fuselage have been initially set:
Your group's job is to provide the complete specifications of your preliminary design, with dimensions of all the areas involved, material used, and the weight and cost of the resulting structure. You should highlight any key tradeoffs such as that between weight and cost that would result by this choice of design and provide suggestions pertaining thereto.
This assignment is divided into two parts. The first part is Home Assignment #9 and is a separate document handed out with this document. This assignment poses a general stiffener-skin configuration similar to those to be considered in Design Problem #4. Your team is asked to determine the cross- section properties of the configuration and the stresses and deflections that arise