Basic knowledge of solid mechanics and design of aerospace structures

The course proposes an experimental approach to the study of the mechanical characteristics of materials and to the measurements of strains and stresses in mechanical components with particular attention to aerospace structures; the principal techniques and standard for the certification of traditional and innovative materials and structures for aeronautical uses will be examined.

At the end of the course the student must know:

• main European and American standard;
• main experimental methods for the evaluation of material characteristics of aerospace materials;
• main experimental methods for measuring displacements, strain and stresses on aerospace components;
• main experimental techniques for non-destructive testing of aerospace structures.

In addition to traditional class lectures supported by the use of a projector, the course also consists of classes dedicated to several applications in laboratories of the experimental techniques described. Some seminars on particular subjects will be planned.

The examination will consist in an oral test. Students will discuss the subjects of the course, demonstrating the knowledge of standard, of experimental methods and their applications.

Load classification, deformation characteristics, generalized Hooke's law, strength criteria.

Standard concerning aeronautical materials. Mechanical tests on conventional and composite materials, metal and polymer foams. Types of tests and test machines. Tensile test. Compression test. Bending test. Fatigue test. Shear test (V-Notched, Rail Shear, Compact Specimen, Two Rail Shear). Compression After Impact Test (CAI).

Notes on the main experimental techniques for the measurement of displacement, deformation and stress.

Strain gauge techniques. Electrical strain gauges (ER). Sensitivity to deformation. Transversal sensitivity. Reinforcement effect of the strain gauge on the specimen. Temperature sensitivity. Insulation resistance, power supply, drift and fatigue life of the strain gauge. Configurations of the measurement circuit. Application of ER technique to composite materials and aerospace structures.

Notes on Optical techniques with particular reference to Digital Image Correlation.

Non-Destructive Testing techniques.

Laboratory tests: Tensile test on a specimen made of metallic and/or composite material, impact test, ultrasonic inspection etc. Applications of Digital Image Correlation to the strength evaluation of aerospace structures.

1. Society for Exper. Mech.: Handbook on Experimental Mechanics. Prentice-Hall, New Jersey, USA, 1987.
2. Dally J.W., Riley W.F.: Experimental Stress Analysis, McGraw Hill, USA, 1987.
3. Standard and class notes.
4. In Italian: Ajovalasit A.: Estensimetri elettrici a resistenza. Aracne Editrice, Roma, 2006.
5. In Italian: Ajovalasit A.: Fotomeccanica. Aracne Editrice, Roma, 2006