Methods for estimating the effect of variations of design variables on the weight of an aircraft component

#The present invention refers to methods for estimating the effect of the variation of design variables on the weight of an aircraft component and more in particular for estimating the effect of variations of material properties.

#Estimating the weight impact due to a variation of a design variable, particularly a material property, is a very common work performed in the design phase of an aircraft when the designer search for an optimized structure. Material improvements can drastically reduce the structural weight and, therefore, diminish the operating costs of the aircraft. Thus, the improvement of the mechanical properties of the manufacturing materials of aircrafts, particularly composite materials, is a permanent goal for aircraft manufacturers. In fact, huge amounts of money are invested in material research.

#However, material improvements will not necessary lead to significant weight reductions. The final weight of a component is the addition of its structural weight and its non-structural weight. The structural weight is driven by the final thickness of its structural elements. From one side, this thickness is related to the structural failures cases that are driven by the material properties, but they are also driven by other requirements that are independent of material properties, so it is difficult to establish a direct relation between the material properties and the structural and overall final weight. Interaction among different failure modes, design constraints, manufacturability and other factors make the relation between material properties and weight difficult to analyze. For instance, if a thin walled structure is sized with a minimum manufacturable thickness, whatever improvement of the Young's module of the material will not have any impact in the structure weight.

#FIG. 1 shows an aircraft component in the torsion box of an horizontal tail plane which is used as an example in the description of a preferred embodiment of this invention.

#FIG. 2 is a cross section of the aircraft component of FIG. 1.

#FIGS. 3 and 4 are, respectively, a cross section and a perspective view of a single stiffener panel of the aircraft component of FIG. 1.

#The weight of an aircraft component made in a given material such a composite material or a metallic material is greatly dependant of its structural element dimensions. Those dimensions are driven by different design criteria, some of which are related to the mechanical properties of the materials like maximum allowable strength, allowable deformations or stability. Other criteria are independent of the mechanical properties of the material like minimum manufacturable thickness, reparability or manufacturing simplicity.

#As there is no a direct relationship between weight and the main design criteria it is difficult to estimate the effect on weight of a variation in a given design variable. Thus, the aim of this invention is to provide simple methods to evaluate the influence on the aircraft component weight of any variation of material properties or any other variable that could affect any design criteria or a group of them, such a minimum manufacturable thickness criteria or the loads applied to the aircraft component.

#The detailed description of this invention will refer to a method for estimating in an aircraft component the effect of a variation of the material properties on the component weight. Similar methods will achieve the same result for the variation of any other design variable as the skilled man will easily understand.