Aircraft Materials and Structures - AETM 4101 - 2024-2025 PDF

Aircraft Materials and Structures AETM 4101 CRN 1444 & CRN 1597 Prepared by Yalcin Faik Sumer 2024 - 2025  Before we start, let us follow some rules ❖ At least 85% attendance is a must. ❖ Punctuality in the Class: Come before the class...

Aircraft Materials and Structures AETM 4101 CRN 1444 & CRN 1597 Prepared by Yalcin Faik Sumer 2024 - 2025  Before we start, let us follow some rules ❖ At least 85% attendance is a must. ❖ Punctuality in the Class: Come before the class time. ❖ Attendance throughout the Class. ❖ No mobile phones unless needed by the instructor. ❖ No food during the class. ❖ Healthy Interactions. ❖ Take notes PLEASE. 2  Learning Objectives ❖ CLO1. Analyze the atomic and crystalline structure of elements. ❖ CLO2. Understand the properties and phase transformation of materials. ❖ CLO3. Analyze the composite materials. ❖ CLO4. Understand the mathematical modelling of elastic structures. ❖ CLO5. Analyze the beam, shaft and thin plate structures. ❖ CLO6. Analyze the different parts of aircraft under loading and Airworthiness. 3  What to be covered?  1. Aircraft materials – Atomic and crystalline structure  2. Aircraft Materials – Imperfection is solids  3. Aircraft Materials – Phase diagram  4. Aircraft Materials ‐ Composite  5. Aircraft Structures ‐ Elasticity  6. Aircraft Structures – Virtual work, Energy methods 4  What to be covered?  7. Aircraft Structures – Thin plate theory  8. Aircraft Structures – Beams and columns  9. Aircraft Structures – Airworthiness  10. Aircraft Structures – Structural analysis of aircraft  11. Aircraft Structures – Vibration of structures 5  Chapter 1 Aircraft materials – Atomic and crystalline structure 6  Aircraft materials – Atomic and crystalline structure Structure The structure of a material usually relates to the arrangement of its internal components. Structural elements may be classified on the basis of size and in this regard there are several levels: 7  Aircraft materials – Atomic and crystalline structure Structure Subatomic structure—involves electrons within the individual atoms, their energies and interactions with the nuclei. Atomic structure—relates to the organization of atoms to yield molecules or crystals. Nanostructure—deals with aggregates of atoms that form particles (nanoparticles) that have nanoscale dimensions (less that about 100 nm). Microstructure—those structural elements that are subject to direct observation using some type of microscope (structural features having dimensions between 100 nm and several millimeters). Macrostructure—structural elements that may be viewed with the naked eye (with scale range between several millimeters and on the order of a meter). Atomic structure, nanostructure, and microstructure of materials are investigated using microscopic techniques 8  Aircraft materials – Atomic and crystalline structure Properties Virtually all important properties of solid materials may be grouped into six different categories: Mechanical properties—relate deformation to an applied load or force; examples include elastic modulus (stiffness), strength, and resistance to fracture. Electrical properties—the stimulus is an applied electric fi eld; typical properties include electrical conductivity and dielectric constant. Thermal properties—are related to changes in temperature or temperature gradients across a material; examples of thermal behavior include thermal expansion and heat capacity. Magnetic properties—the responses of a material to the application of a magnetic field; common magnetic properties include magnetic susceptibility and magnetization. Optical properties—the stimulus is electromagnetic or light radiation; index of refraction and reflectivity are representative optical properties. 9  Aircraft materials – Atomic and crystalline structure Properties Three thin disk specimens of aluminum oxide that have been placed over a printed page in order to demonstrate their differences in light-transmittance characteristics. The disk on the left is transparent (i.e., virtually all light that is reflected from the page passes through it), whereas the one in the center is translucent (meaning that some of this reflected light is transmitted through the disk). The disk on the right is opaque—that is, none of the light passes through it. These differences in optical properties are a consequence of differences in structure of these materials, which have resulted from the way the materials were processed 10  Aircraft materials – Atomic and crystalline structure Properties The four components of the discipline of materials science and engineering and their interrelationship 11  Aircraft materials – Atomic and crystalline structure Properties An engineer has the option of selecting a best material from the thousands available. The final decision is normally based on several criteria. First, the in-service conditions must be characterized, for these dictate the properties required of the material. Only on rare occasions does a material possess the optimum or ideal combination of properties. Thus, it may be necessary to trade one characteristic for another. The classic example involves strength and ductility; normally, a material having a high strength has only a limited ductility. In such cases, a reasonable compromise between two or more properties may be necessary. 12  Aircraft materials – Atomic and crystalline structure Properties A second selection consideration is any deterioration of material properties that may occur during service operation. For example, significant reductions in mechanical strength may result from exposure to elevated temperatures or corrosive environments MRO professionals, as it enables them to implement adequate preventive measures and inspection protocols, ensuring the longevity, safety, and reliability of aircraft components, where various types of corrosion in aircraft can be a significant threat to the integrity and safety of metal structures. 13  Aircraft materials – Atomic and crystalline structure Properties Corrosion in aft cargo compartment 14  Aircraft materials – Atomic and crystalline structure Properties Finally, probably the overriding consideration is that of economics: What will the finished product cost? A material may be found that has the optimum set of properties but is prohibitively expensive. Here again, some compromise is inevitable. The cost of a finished piece also includes any expense incurred during fabrication to produce the desired shape. 15  Aircraft materials – Atomic and crystalline structure Properties CASE STUDY – LEARNING FROM MISTAKES –SHIP FAILURES Analyze mechanical failures, determine their causes, and then propose appropriate measures to guard against future incidents. Dramatic example of the brittle fracture of steel that was thought to be ductile Some of the early ships experienced structural damage when cracks developed in their decks and hulls. Three of them catastrophically split in half when cracks formed, grew to critical lengths, and then rapidly propagated completely around the ships’ girths. 16  Aircraft materials – Atomic and crystalline structure Properties CASE STUDY – LEARNING FROM MISTAKES –SHIP FAILURES Picture shows one of the ships that fractured the day after it was launched. Subsequent investigations concluded one or more of the following factors contributed to each failure: When some normally ductile metal alloys are cooled to relatively low temperatures, they become susceptible to brittle fracture—that is, they experience a ductile-to-brittle transition upon cooling through a critical range of temperatures. 17  Aircraft materials – Atomic and crystalline structure Properties CASE STUDY – LEARNING FROM MISTAKES –SHIP FAILURES The corner of each hatch (i.e., door) was square; these corners acted as points of stress concentration where cracks can form. Boeing 787 Doors and windows load analysis 18  Aircraft materials – Atomic and crystalline structure Properties CASE STUDY – LEARNING FROM MISTAKES –SHIP FAILURES Welding vs. Rivet Using prefabricated steel sheets that were assembled by welding rather than by the traditional time-consuming riveting. Unfortunately, cracks in Weld defects and discontinuities welded structures may propagate unimpeded for (i.e., sites where cracks can large distances, which can lead to catastrophic form) were introduced by failure. However, when structures are riveted, a inexperienced operators crack ceases to propagate once it reaches the edge of a steel sheet. 19  Aircraft materials – Atomic and crystalline structure Properties CASE STUDY – LEARNING FROM MISTAKES –SHIP FAILURES 20  Aircraft materials – Atomic and crystalline structure Properties TO PREVENT SUCH FAILURES ▪ Lowering the ductile-to-brittle temperature of the steel to an acceptable level by improving steel quality (e.g., reducing sulfur and phosphorus impurity contents). ▪ Rounding off hatch corners by welding a curved reinforcement strip on each corner. ▪ Installing crack-arresting devices such as riveted straps and strong weld seams to stop propagating cracks. ▪ Improving welding practices and establishing welding codes 21  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Solid materials have been conveniently grouped into three basic categories: Metals Chemical makeup and Atomic structure Ceramics Polymers 22  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Another category is advanced materials—those used in high-technology applications, such as semiconductors, biomaterials, smart materials, and nanoengineered materials 23  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Metals: Metals are composed of one or more metallic elements (e.g., iron, aluminum, copper, titanium, gold, nickel), and often also nonmetallic elements (e.g., carbon, nitrogen, oxygen) in relatively small amounts. Atoms in metals and their alloys are arranged in a very orderly manner and are relatively dense in comparison to the ceramics and polymers. 24  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS With regard to mechanical characteristics, these materials are relatively stiff and strong, yet are ductile (i.e., capable of large amounts of deformation without fracture), and are resistant to fracture, which accounts for their widespread use in structural applications. Metallic materials have large numbers of nonlocalized electrons—that is, these electrons are not bound to particular atoms. Many properties of metals are directly attributable to these electrons. For example, metals are extremely good conductors of electricity (Figure 1.8) and heat, and are not transparent to visible light; a polished metal surface has a lustrous appearance. In addition, some of the metals (i.e., Fe, Co, and Ni) have desirable magnetic properties. 25  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 26  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Bar chart of room temperature density values for various metals, ceramics, polymers, and composite materials. 27  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Bar chart of room temperature stiffness (i.e., elastic modulus) values for various metals, ceramics, polymers, and composite materials. 28  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Bar chart of room temperature strength (i.e., tensile strength) values for various metals, ceramics, polymers, and composite materials 29  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Bar chart of room-temperature resistance to fracture (i.e., fracture toughness) for various metals, ceramics, polymers, and composite materials 30  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Bar chart of room temperature electrical conductivity ranges for metals, ceramics, polymers, and semiconducting materials. 31  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Ceramics: Ceramics are compounds between metallic and nonmetallic elements; they are most frequently oxides, nitrides, and carbides. For example, common ceramic materials include aluminum oxide (or alumina, Al2O3), silicon dioxide (or silica, SiO2), silicon carbide (SiC), silicon nitride (Si3N4), and, in addition, what some refer to as the traditional ceramics—those composed of clay minerals (e.g., porcelain), as well as cement and glass. 32  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS With regard to mechanical behavior, ceramic materials are relatively stiff and strong—stiffnesses and strengths are comparable to those of the metals. In addition, they are typically very hard. Historically, ceramics have exhibited extreme brittleness (lack of ductility) and are highly susceptible to fracture. However, newer ceramics are being engineered to have improved resistance to fracture; these materials are used for cookware, cutlery, and even automobile engine parts. 33  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Furthermore, ceramic materials are typically insulative to the passage of heat and electricity (i.e., have low electrical conductivities), and are more resistant to high temperatures and harsh environments than are metals and polymers. With regard to optical characteristics, ceramics may be transparent, translucent, or opaque, and some of the oxide ceramics (e.g., Fe3O4) exhibit magnetic behavior. Several common ceramic objects are shown in The characteristics, types, and applications of this class of materials will be discussed later. 34  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 35  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Polymers: Polymers include the familiar plastic and rubber materials. Many of them are organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements (i.e., O, N, and Si). Furthermore, they have very large molecular structures, often chainlike in nature, that often have a backbone of carbon atoms. 36  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Some common and familiar polymers are polyethylene (PE), nylon, poly (vinyl chloride) (PVC), polycarbonate (PC), polystyrene (PS), and silicone rubber. These materials typically have low densities, whereas their mechanical characteristics are generally dissimilar to those of the metallic and ceramic materials—they are not as stiff or strong as these other material types. 37  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS However, on the basis of their low densities, many times their stiffnesses and strengths on a per-mass basis are comparable to those of the metals and ceramics. In addition, many of the polymers are extremely ductile and pliable (i.e., plastic), which means they are easily formed into complex shapes. 38  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS In general, they are relatively inert chemically and unreactive in a large number of environments. Furthermore, they have low electrical conductivities and are nonmagnetic. One major drawback to the polymers is their tendency to soften and/or decompose at modest temperatures, which, in some instances, limits their use. 39  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 40  Aircraft materials – Atomic and crystalline structure Case Study CARBONATED BEVARAGE CONTAINERS Define 6 specifications 41  Aircraft materials – Atomic and crystalline structure Case Study CARBONATED BEVARAGE CONTAINERS provide a barrier to the passage of carbon dioxide, which is under pressure in the container; be nontoxic, unreactive with the beverage, and, preferably, recyclable; be relatively strong and capable of surviving a drop from a height of several feet when containing the beverage; be inexpensive, including the cost to fabricate the final shape if optically transparent, retain its optical clarity; and be capable of being produced in different colors and/or adorned with decorative labels. 42  Aircraft materials – Atomic and crystalline structure Case Study CARBONATED BEVARAGE CONTAINERS All three of the basic material types—metal (aluminum), ceramic (glass), and polymer (polyester plastic)—are used for carbonated beverage containers (per the chapter- opening photographs). All of these materials are nontoxic and unreactive with beverages. In addition, each material has its pros and cons. For example, the aluminum alloy is relatively strong (but easily dented), is a very good barrier to the diffusion of carbon dioxide, is easily recycled, cools beverages rapidly, and allows labels to be painted onto its surface. However, the cans are optically opaque and relatively expensive to produce. 43  Aircraft materials – Atomic and crystalline structure Case Study CARBONATED BEVARAGE CONTAINERS Glass is impervious to the passage of carbon dioxide, is a relatively inexpensive material, and may be recycled, but it cracks and fractures easily, and glass bottles are relatively heavy. Whereas plastic is relatively strong, may be made optically transparent, is inexpensive and lightweight, and is recyclable, it is not as impervious to the passage of carbon dioxide as aluminum and glass. For example, you may have noticed that beverages in aluminum and glass containers retain their carbonization (i.e., “fizz”) for several years, whereas those in two-liter plastic bottles “go flat” within a few months. 44  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Composites: A composite is composed of two (or more) individual materials that come from the categories previously discussed—metals, ceramics, and polymers. The design goal of a composite is to achieve a combination of properties that is not displayed by any single material and also to incorporate the best characteristics of each of the component materials. 45  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Composites: A large number of composite types are represented by different combinations of metals, ceramics, and polymers. One of the most common and familiar composites is fiberglass, in which small glass fibers are embedded within a polymeric material (normally an epoxy or polyester).The glass fibers are relatively strong and stiff (but also brittle), whereas the polymer is more flexible. Thus, fiberglass is relatively stiff, strong and flexible. In addition, it has a low density 46  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Translucent fiberglass Fiber glass sheets 47  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Close view of glass fibers 48  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Another technologically important material is the carbon fiber–reinforced polymer (CFRP) composite—carbon fibers that are embedded within a polymer. These materials are stiffer and stronger than glass fiber–reinforced materials but more expensive. CFRP composites are used in some aircraft and aerospace applications, as well as in high-tech sporting equipment (e.g., bicycles, golf clubs, tennis rackets, skis/ snowboards) and recently in automobile bumpers. The new Boeing 787 fuselage is primarily made from such CFRP composites. 49  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Carbon fiber wing repair 50  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Close view carbon fiber 51  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS A380 material 52  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS B787 material 53  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Elastomers—polymeric materials that display rubbery-like behavior (high degrees of elastic deformation). Natural materials—those that Stiffness vs. density occur in nature; for example, wood, leather, and cork. Foams—typically polymeric materials that have high porosities (contain a large volume fraction of small pores), which are often used for cushions and packaging 54  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Advanced materials: Semiconductors Biomaterials Smart materials Nanomaterials 55  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Advanced materials: Materials utilized in high-technology (or high-tech) applications are sometimes termed advanced materials. By high technology, we mean a device or product that operates or functions using relatively intricate and sophisticated principles, including electronic equipment (cell phones, DVD players, etc.), computers, fiber-optic systems, high-energy density batteries, energy-conversion systems, and aircraft. 56  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Semiconductors: Semiconductors have electrical properties that are intermediate between those of electrical conductors (i.e., metals and metal alloys) and insulators (i.e., ceramics and polymers. Furthermore, the electrical characteristics of these materials are extremely sensitive to the presence of minute concentrations of impurity atoms, for which the concentrations may be controlled over very small spatial regions. Semiconductors have made possible the advent of integrated circuitry that has totally revolutionized the electronics and computer industries (not to mention our lives) over the past four decades. 57  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Semiconductors, sometimes referred to as integrated circuits (ICs) or microchips, are made from pure elements, typically silicon or germanium, or compounds such as gallium arsenide. Semiconductor is a substance often used in electrical circuits and components that partially conducts electricity, allowing electrons to flow throughout the circuit when a certain voltage is applied. 58  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Biomaterials: The length and the quality of our lives are being extended and improved, in part, due to advancements in the ability to replace diseased and injured body parts. Replacement implants are constructed of biomaterials—nonviable (i.e., nonliving) materials that are implanted into the body, so that they function in a reliable, safe, and physiologically satisfactory manner, while interacting with living tissue. That is, biomaterials must be biocompatible—compatible with body tissues and fluids with which they are in contact over acceptable time periods. Biocompatible materials must neither elicit rejection or physiologically unacceptable responses nor release toxic substances. Consequently, some rather stringent constraints are imposed on materials in order for them to be biocompatible. 59  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Biomaterials: Suitable biomaterials are to be found among the several classes of materials discussed earlier in this chapter—i.e., metal alloys, ceramics, polymers, and composite materials. Throughout the remainder of this book we draw the reader’s attention to those materials that are used in biotechnology applications. Over the past several years the development of new and better biomaterials has accelerated rapidly. Example biomaterial applications include joint (e.g., hip, knee) and heart valve replacements, vascular (blood vessel) grafts, fracture-fixation devices, dental restorations, and generation of new organ tissues. 60  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 61  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 62  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Smart Materials: Smart (or intelligent) materials are a group of new and state-of-the-art materials now being developed that will have a significant influence on many of our technologies. The adjective smart implies that these materials are able to sense changes in their environment and then respond to these changes in predetermined manners—traits that are also found in living organisms. In addition, this smart concept is being extended to rather sophisticated systems that consist of both smart and traditional materials. Components of a smart material (or system) include some type of sensor (which detects an input signal) and an actuator (which performs a responsive and adaptive function). Actuators may be called upon to change shape, position, natural frequency, or mechanical characteristics in response to changes in temperature, electric fields, and/or magnetic fields. 63  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Smart Materials: Four types of materials are commonly used for actuators: shape-memory alloys, piezoelectric ceramics, magnetostrictive materials, and electrorheological/magnetorheological fluids. Shape-memory alloys are metals that, after having been deformed, revert to their original shape when temperature is changed. Piezoelectric ceramics expand and contract in response to an applied electric field (or voltage); conversely, they also generate an electric field when their dimensions are altered. The behavior of magnetostrictive materials is analogous to that of the piezoelectrics, except that they are responsive to magnetic fields. Also, electrorheological and magnetorheological fluids are liquids that experience dramatic changes in viscosity upon the application of electric and magnetic fields, respectively. 64  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Shape Memory Alloys 65  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Shape Memory Alloys 66  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Some of our Piezoelectric ceramic applications include: Medical – Bone conduction hearing aids, Ultrasonic surgical instruments, Micro- and nano-dosing equipment Communications – Antennas, Sensors Optics – Fiber positioning, turntable lasers Automotive – Knock sensors, Fuel injectors Commercial – Alarms, Buzzers, Printers 67  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 68  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 69  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Smart Materials: For example, one type of smart system is used in helicopters to reduce aerodynamic cockpit noise created by the rotating rotor blades. Piezoelectric sensors inserted into the blades monitor blade stresses and deformations; feedback signals from these sensors are fed into a computer-controlled adaptive device that generates noise-canceling antinoise. 70  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Nanomaterials: One new material class that has fascinating properties and tremendous technological promise is the nanomaterials, which may be any one of the four basic types—metals, ceramics, polymers, or composites. However, unlike these other materials, they are not distinguished on the basis of their chemistry but rather their size; the nano prefix denotes that the dimensions of these structural entities are on the order of a nanometer (10−9 m)—as a rule, less than 100 nanometers (nm; equivalent to the diameter of approximately 500 atoms). 71  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Nanomaterials: Some of the physical and chemical characteristics exhibited by matter may experience dramatic changes as particle size approaches atomic dimensions. For example, materials that are opaque in the macroscopic domain may become transparent on the nanoscale; some solids become liquids, chemically stable materials become combustible, and electrical insulators become conductors. Furthermore, properties may depend on size in this nanoscale domain. Some of these effects are quantum mechanical in origin, whereas others are related to surface phenomena—the proportion of atoms located on surface sites of a particle increases dramatically as its size decreases. 72  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Nanomaterials: Because of these unique and unusual properties, nanomaterials are finding niches in electronic, biomedical, sporting, energy production, and other industrial applications. Some are discussed in this text, including the following: Catalytic converters for automobiles Nanocarbons—fullerenes, carbon nanotubes, and graphene Particles of carbon black as reinforcement for automobile tires Nanocomposites Magnetic nanosize grains that are used for hard disk drives Magnetic particles that store data on magnetic tapes 73  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS Nanometer-scale materials can be stronger, more durable, and more conductive than their larger-scale (called bulk) counterparts. How does nanotechnology work step by step? Instead of manufacturing materials by cutting down on massive amounts of material, nanotechnology uses the reverse engineering principle, which operates in nature. It allows the manufacturing of products at the nano scale, such as atoms, and then develops products to work at a deeper scale 74  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 75  Aircraft materials – Atomic and crystalline structure CLASSIFICATION OF MATERIALS 76  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure Commonly used metals 77  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure 78  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure 79  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure 80  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure 81  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure Crystalline structure Atoms of pure metal are arranged in a regular grid and packed together 82  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure Glass atoms are arranged randomly They are called amorphous material 83  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure Repeating number of identical units 84  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure There are several number of different unit cells MOST COMMON ONES FOR METALS 85  Aircraft materials – Atomic and crystalline structure Atomic and crystalline structure Packing factor of unit cells It is about how much they can fill the unit cell volume This is also directly related with density Metals have higher packing factor and higher density 86