Scheda di revisione: Aerospace Structural Materials and Design

📋 Course Outline

1. Elasticity & Basic Principles
2. Material Properties & Failure
3. Structural Analysis & Loads
4. Material Selection & Properties
5. Composite Materials & Types
6. Stress & Strain Analysis
7. Finite Element Method & Discretization
8. Structural Elements & Functions
9. Fracture & Failure Theories
10. Design & Structural Optimization

📖 1. Elasticity & Basic Principles

🔑 Key Concepts & Definitions

• Elasticity: The property of a material to return to its original shape after deformation when the applied load is removed. Deformations disappear completely, indicating a reversible behavior.

• Ductility: The ability of a solid material to undergo significant plastic deformation under tensile stress before fracture, providing warning of failure through visible strain.

• Strength: The maximum stress a material can withstand without failure, whether tensile, compressive, or shear.

• Toughness: The capacity of a material to absorb energy and plastically deform without fracturing; a balance of strength and ductility.

• Brittleness: The tendency of a material to fracture with little to no plastic deformation (strain typically below 5%), often failing suddenly without warning.

• Fatigue: The weakening of a material caused by cyclic loading, which can lead to failure after many small stress cycles below the breaking stress.

📝 Essential Points

• Material Selection Factors: Strength-to-weight ratio is paramount; other properties include stiffness, toughness, corrosion resistance, fatigue life, ease of fabrication, availability, and cost.

• Elastic vs Plastic Behavior:

  • Elastic materials recover all deformation upon load removal.
  • Plastic materials exhibit permanent deformation after load removal; elastoplastic behavior occurs when materials behave elastically up to the elastic limit and plastically thereafter.

• Material Failure Modes:

  • Fracture due to excessive stress.
  • Fatigue failure after cyclic loading.
  • Corrosion leading to gradual material degradation.

• Mechanical Properties of Materials:

  • Aluminum alloys: Low density, high strength, good fatigue resistance, but susceptible to corrosion.
  • Titanium alloys: High fatigue and tensile strength, high temperature resistance, corrosion resistant, but costly and dense.
  • Steel: High strength and stiffness, heavier, used mainly for small components requiring high load capacity.
  • Composite materials: High strength-to-weight ratio, anisotropic properties, used increasingly in primary and secondary structures.

• Material Failures & Inspections:

  • Failures include fractures, fatigue cracks, corrosion.
  • Non-Destructive Testing (NDT) methods are critical for detecting hidden damages.

💡 Key Takeaway

Elasticity is fundamental in aerospace structures, enabling materials to withstand loads without permanent deformation; selecting the right material involves balancing strength, weight, durability, and cost to ensure safety and performance.

📖 2. Material Properties & Failure

🔑 Key Concepts & Definitions

• Ductility: The ability of a material to undergo significant plastic deformation under tensile stress before failure, indicated by large strains and warning signs of failure.

• Strength: The maximum stress a material can withstand without failure, including tensile, compressive, and shear strength.

• Toughness: The capacity of a material to absorb energy and plastically deform without fracturing; a balance of strength and ductility.

• Brittleness: The tendency of a material to fracture with minimal deformation (strain below 5%), often failing suddenly without warning.

• Elasticity: The property of a material to return to its original shape after the removal of applied load; characterized by reversible deformation.

• Fatigue: The progressive and localized structural damage that occurs when a material is subjected to cyclic loading below its ultimate strength, potentially leading to failure over many cycles.

📝 Essential Points

• Material selection for aircraft emphasizes a combination of strength and lightness, with additional considerations such as stiffness, toughness, corrosion and fatigue resistance, ease of fabrication, availability, and cost.

• Ductility provides warning before failure, while brittle materials fail suddenly with little warning, often below 5% strain.

• Elastic materials recover their shape after load removal; plasticity involves permanent deformation, with elastoplastic behavior occurring near the elastic limit.

• Toughness reflects a material's ability to absorb energy; high toughness indicates good resistance to crack propagation and impact.

• Fatigue failure results from cyclic loads, with aircraft components often tested for three times their expected lifecycle to ensure durability.

• Corrosion involves chemical reactions (oxidation) leading to material degradation; prevention methods include painting, anodizing, cladding, and cadmium plating.

• Material properties vary among aluminum alloys, titanium, steels, and composites, influencing their suitability for different aircraft components.

• Titanium alloys offer high fatigue and temperature resistance but are costly and dense; used mainly in demanding engine parts.

• Steel provides high strength and stiffness but is heavy, used mainly for small castings and critical fasteners.

• Aluminum alloys are favored for their low weight and improved mechanical properties through alloying, used extensively in airframes and skins.

• Composite materials (fiber-reinforced plastics) provide high strength-to-weight ratios, corrosion resistance, and fatigue durability, increasingly replacing metals in aircraft structures.

💡 Key Takeaway

Material properties such as ductility, strength, toughness, and fatigue resistance are critical in designing aircraft structures that are lightweight, durable, and safe. The choice of materials—metals or composites—must balance these properties to meet performance, safety, and economic requirements.

📖 3. Structural Analysis & Loads

🔑 Key Concepts & Definitions

• Structural Loads: External forces or moments acting on an aircraft structure during operation, classified into ground loads (taxiing, landing, towing) and air loads (during flight).
• Fuselage Loads: Forces experienced by the fuselage due to payload weight, pressurization, maneuvering, and landing impacts, including bending, tension, compression, and shear.
• Wing Loads: Forces on the wing caused by lift, including shear forces, bending moments, and torsion, especially concentrated at the root.
• Pressurization Loads: Internal cabin pressure exerting tension or compression on fuselage walls, especially around doors, windows, and cutouts.
• Structural Elements: Components like frames, stringers, spars, ribs, bulkheads, and skin that provide strength, stiffness, and shape to aircraft structures.
• Load Path: The route through which loads are transferred from the point of application to the aircraft’s main structural elements, ensuring load distribution and safety.

📝 Essential Points

• Aircraft structures must withstand diverse loads: static (e.g., weight, payload) and dynamic (e.g., turbulence, maneuvers).
• Fuselage design involves reinforcement around cutouts (doors, windows) to maintain load integrity; pressurization causes significant internal stresses.
• Wing structure includes spars, ribs, and stringers; the root experiences maximum shear and bending moments, requiring high strength and stiffness.
• Tail components (tailplane, rudder) generate lift and torsion, influencing fuselage stress distribution.
• Landing gear absorbs shock during landing; shock absorbers and brakes dissipate energy to prevent structural damage.
• Load transfer involves careful design of structural elements to ensure safety under all operational conditions, including emergency scenarios like depressurization.

💡 Key Takeaway

Aircraft structural integrity relies on a complex interplay of loads and carefully designed load paths, ensuring safety and performance through reinforced fuselage, wing, and landing gear components capable of handling static and dynamic forces during all flight phases.

📖 4. Material Selection & Properties

🔑 Key Concepts & Definitions

• Ductility: The ability of a material to undergo significant plastic deformation under tensile stress before fracture, providing warning of failure through visible deformation.

• Strength: The maximum stress a material can withstand without failure, including tensile, compressive, or shear strength.

• Toughness: The capacity of a material to absorb energy and plastically deform without fracturing; a balance of strength and ductility.

• Brittleness: The tendency of a material to fracture with minimal deformation (strain typically below 5%), often failing suddenly without warning.

• Elasticity: The property of a material to return to its original shape after deformation when the load is removed.

• Fatigue: The weakening of a material caused by repeated cyclic loading below the breaking stress, potentially leading to failure after many cycles.

📝 Essential Points

• Material selection for aircraft prioritizes strength-to-weight ratio, with additional considerations for stiffness, toughness, corrosion resistance, fatigue life, fabrication ease, availability, and cost.

• Ductility warns of failure through deformation, aiding maintenance and safety; brittle materials fail suddenly with little warning.

• Elastic materials recover their shape after load removal, whereas plastic materials undergo permanent deformation.

• Fatigue is critical in aircraft design; components are often tested for three times their expected lifecycle to ensure durability.

• Corrosion resistance is vital; methods include painting, anodizing, cladding, and cadmium plating to protect metals.

• Materials in aircraft:

  • Titanium alloys: High strength, fatigue resistance, high-temperature stability, but costly and dense; used in engine parts.
  • Steels: High tensile strength, used in small components like fasteners and landing gear pivots.
  • Aluminum alloys: Low density, good strength, widely used; alloy series (2000, 5000, 6000, 7000, 8000) tailored for specific properties.
  • Composite materials: Fiber-reinforced plastics (FRPs) like CFRP offer high strength-to-weight ratios, used extensively in modern aircraft structures.

• Composite materials:

  • Made from fibers (glass, carbon, Kevlar) embedded in a matrix (epoxy, plastic).
  • Laminated composites: Multiple fiber layers for high in-plane strength; susceptible to delamination.
  • Sandwich composites: Core material between face sheets for high stiffness and lightweight structures.

💡 Key Takeaway

Selecting aircraft materials involves balancing strength, weight, durability, and cost; advanced composites now play a pivotal role in reducing weight and enhancing performance, but require careful consideration of their anisotropic and brittle nature.

📖 5. Composite Materials & Types

🔑 Key Concepts & Definitions

• Composite Material: A material made from two or more constituent materials with significantly different physical or chemical properties, combined to produce a new material with enhanced characteristics.

• Fiber-Reinforced Polymer (FRP): A composite where fibers such as glass, carbon, or aramid are embedded in a polymer matrix (e.g., epoxy), providing high strength and stiffness.

• Laminated Composite: A composite made by stacking multiple fibrous layers (plies) bonded with a matrix, characterized by high in-plane strength but potential delamination issues.

• Sandwich Composite: A composite structure with two thin, stiff face sheets bonded to a lightweight core, offering high bending stiffness and strength with minimal weight.

• Delamination: A failure mode in laminated composites where layers separate due to poor interlaminar bonding or loading, compromising structural integrity.

• Torsion-Box Structure: A structural configuration in wings where spars and skin form a closed box to resist torsion and bending loads effectively.

📝 Essential Points

• Material Composition: Composites combine fibers (strength and stiffness) with matrices (binding and protection), resulting in anisotropic properties dependent on fiber orientation.

• Advantages of Composites:

  • High strength-to-weight ratio
  • Corrosion resistance
  • Design flexibility
  • Damage tolerance (especially with 3D architectures)
  • Reduced structural weight (e.g., CFRP can reduce weight by ~12%)

• Types of Composite Architectures:

  • Laminated composites: Assembled from multiple layers; susceptible to delamination, but can be enhanced with 3D fiber architectures.
  • Sandwich composites: Face sheets + core; ideal for primary structures requiring high bending stiffness with low weight.

• Applications in Aerospace:

  • Primary and secondary structural parts (wings, fuselage sections)
  • Engine components
  • Radomes, antenna dishes
  • Landing gear doors
  • Tail stabilizers

• Growth Trends:

  • Increasing use in commercial aircraft (e.g., Boeing 787 with >50% composites)
  • Significant cost and weight savings
  • Future prospects include ceramic matrix composites for high-temperature engine parts

• Limitations:

  • Poor through-the-thickness properties in laminated composites
  • Delamination risk
  • Brittle nature of some fibers (e.g., CFRP)
  • Moisture absorption affecting matrix properties

💡 Key Takeaway

Composite materials, especially fiber-reinforced plastics, revolutionize aerospace design by providing high strength and stiffness with minimal weight, enabling more efficient, durable, and innovative aircraft structures. However, their anisotropic nature and failure modes require careful design and manufacturing strategies.

📖 6. Stress & Strain Analysis

🔑 Key Concepts & Definitions

• Stress: Force per unit area within materials arising from externally applied loads, expressed in units such as Pascals (Pa). Types include tensile, compressive, shear, and torsional stresses.

• Strain: The measure of deformation representing the relative displacement between particles in a material caused by stress, typically expressed as a dimensionless ratio or percentage.

• Elasticity: The property of a material to return to its original shape after removing the applied load, characterized by a linear stress-strain relationship within the elastic limit.

• Hooke’s Law: A fundamental principle stating that, within the elastic limit, stress is directly proportional to strain (σ = Eε), where E is the modulus of elasticity.

• Torsion: A type of shear stress resulting from twisting of a material about its longitudinal axis, commonly analyzed in shafts and circular sections.

• Bending: The deformation of a structure subjected to transverse loads, producing tension on one side and compression on the opposite side of the neutral axis.

📝 Essential Points

• Stress-Strain Relationship: In elastic materials, stress and strain are linearly related up to the elastic limit; beyond this, plastic deformation occurs.

• Material Behavior: Different materials exhibit varying elastic and plastic responses; ductile materials deform significantly before failure, while brittle materials fail with minimal deformation.

• Stress Analysis Methods:

  • Direct methods: Calculating stresses directly from applied loads and geometry.
  • Energy methods: Using strain energy principles to analyze complex structures.
  • Torsion analysis: Employing shear stress formulas for circular shafts.
  • Bending analysis: Using moment-curvature relationships to determine stresses in beams and plates.

• Structural Stability & Instability: Structures must be designed to avoid buckling and other forms of instability, especially in thin-walled aerospace components.

• Material Properties Impact:

  • Ductility allows warning before failure.
  • Toughness indicates energy absorption capacity.
  • Brittleness leads to sudden failure with little warning.
  • Corrosion can degrade material strength over time, affecting stress analysis.

• Load Types in Aircraft Structures:

  • Ground loads: During taxiing, landing, towing.
  • Air loads: Aerodynamic forces during flight.
  • Body forces: Gravity, inertial effects.

• Material Selection Factors:

  • Strength-to-weight ratio.
  • Resistance to fatigue, corrosion.
  • Ease of fabrication and cost.

💡 Key Takeaway

Stress and strain analysis in aerospace structures involves understanding material behavior under various loads to ensure safety, optimize weight, and prevent failure through appropriate material selection and structural design.

📖 7. Finite Element Method & Discretization

🔑 Key Concepts & Definitions

• Finite Element Method (FEM): A numerical technique for solving complex structural, thermal, and fluid problems by subdividing a large system into smaller, simpler parts called finite elements, which are interconnected at nodes.

• Discretization: The process of dividing a continuous domain (such as a structure or a field) into finite elements, transforming a continuous problem into a finite set of algebraic equations.

• Mesh: A network of elements and nodes that discretizes the domain; the quality and density of the mesh influence the accuracy and computational cost of FEM analysis.

• Element: The basic building block in FEM, representing a simple shape (e.g., triangle, quadrilateral, tetrahedron) over which equations are approximated.

• Shape Functions: Mathematical functions used within elements to interpolate the unknown field variables (displacements, temperatures, etc.) based on nodal values.

• Assembly: The process of combining element equations into a global system that models the entire structure or domain.

📝 Essential Points

• FEM transforms complex differential equations governing physical phenomena into algebraic equations suitable for computer solution, enabling analysis of intricate geometries and boundary conditions.

• Discretization involves meshing the domain into elements; finer meshes generally increase accuracy but require more computational resources.

• The choice of element type (e.g., 2D, 3D, linear, quadratic) affects the approximation quality and convergence rate.

• Shape functions approximate the variation of unknowns within each element; their order determines the element's interpolation capability.

• Proper mesh quality (element shape, size, and distribution) is critical to obtaining reliable results; poor meshing can lead to inaccuracies or convergence issues.

• Boundary conditions and loads are applied at nodes or elements, influencing the solution of the assembled system.

• The FEM process involves four main steps: pre-processing (meshing and defining properties), solving (assembling and solving equations), post-processing (visualizing results), and validation.

💡 Key Takeaway

Finite Element Method discretizes complex structures into manageable elements, enabling detailed analysis of stresses, strains, and other physical phenomena through numerical approximation, with mesh quality being vital for accurate results.

📖 8. Structural Elements & Functions

🔑 Key Concepts & Definitions

• Fuselage: The main body of an aircraft that carries payload, passengers, and supports structural loads such as bending, torsion, and pressurization.
• Wing: An aerodynamic surface that generates lift; composed of internal structure (spars, ribs, stringers) and external skin.
• Spars: Primary load-bearing beams running spanwise in wings, resisting bending and shear forces.
• Ribs: Structural components that give shape to the wing, support the skin, and prevent buckling.
• Stringers: Longitudinal stiffeners attached to the skin to resist compression and torsion.
• Pressurized Shell: The fuselage's stressed skin, reinforced with frames and bulkheads to withstand internal cabin pressure.
• Torsion-Box: A structural configuration where spars and skin form a closed box to resist torsional loads.
• Landing Gear: Supports the aircraft on the ground, absorbs shocks during landing, and facilitates taxiing.
• Composite Materials: Hybrid materials made from fibers (e.g., carbon, glass) embedded in a matrix (e.g., epoxy), offering high strength-to-weight ratios.
• Laminated Composites: Layers of fibrous material combined with a matrix, optimized for in-plane strength but vulnerable to delamination.
• Sandwich Composites: Structures with a lightweight core between two face sheets, providing high stiffness and strength with low weight.

📝 Essential Points

• Structural Functions:
  • The fuselage must withstand bending, torsion, and pressurization loads while minimizing weight.
  • Wings generate lift and resist aerodynamic bending, shear, and torsion; spars and ribs are critical for load distribution.
  • The tail stabilizers provide torsional stability and control.
  • Landing gear absorbs impact loads during landing and supports aircraft on the ground.
• Material Selection:
  • Strength, lightness, stiffness, toughness, corrosion resistance, and fatigue life are key criteria.
  • Titanium alloys excel in high-temperature, high-stress areas like turbine blades.
  • Aluminum alloys are widely used for their low weight and good mechanical properties.
  • Steel is used for small, high-strength components due to its high density.
  • Composites, especially CFRP, are increasingly replacing metals for weight savings and high performance.
• Loads on Aircraft Structures:
  • Ground loads include taxiing, landing, and towing forces.
  • Air loads involve aerodynamic forces during flight, including lift, drag, and torsion.
  • Fuselage experiences internal pressure, especially in pressurized cabins, causing bending and tension.
  • Wing loads are highest at the root, where shear forces and bending moments concentrate.
  • Fuel distribution affects load balancing; tanks are often emptied from the root to the tip.
• Design Considerations:
  • Structural elements must balance strength and weight efficiency.
  • Reinforcements like frames, bulkheads, and stringers are essential for maintaining shape and integrity.
  • The use of advanced composites allows significant weight reduction, improving fuel efficiency and payload capacity.

💡 Key Takeaway

Aircraft structural elements are meticulously designed to withstand diverse loads while minimizing weight, with material choice and structural configuration playing crucial roles in ensuring safety, performance, and efficiency. Advances in composite materials are transforming aircraft design by enabling lighter, stronger, and more durable structures.

📖 9. Fracture & Failure Theories

🔑 Key Concepts & Definitions

• Fracture: The separation or cracking of a material into two or more pieces due to stress exceeding its strength. It can be brittle or ductile.
• Failure: The inability of a material or structure to perform its intended function, often caused by exceeding strength limits or fatigue.
• Stress: Internal force per unit area within a material, caused by external loads, expressed as tensile, compressive, or shear stress.
• Strain: The deformation or displacement per unit length resulting from applied stress.
• Fracture Toughness (K_IC): A material's ability to resist crack propagation, indicating its resistance to fracture in the presence of flaws.
• Failure Theories: Mathematical models predicting the failure of materials under complex loading, including maximum normal stress, maximum shear stress, and distortion energy theories.

📝 Essential Points

• Types of Failure:
  • Brittle failure: Sudden fracture with minimal deformation, often with little warning.
  • Ductile failure: Significant plastic deformation before fracture, providing warning signs.
• Failure Criteria:
  • Maximum Normal Stress Theory: Failure occurs when the maximum principal stress exceeds the material's tensile strength.
  • Maximum Shear Stress Theory: Failure occurs when shear stress reaches the shear strength.
  • Distortion Energy (von Mises) Theory: Failure occurs when the energy of distortion exceeds a critical value, suitable for ductile materials.
• Crack Propagation:
  • Initiated at flaws or cracks within the material.
  • Governed by fracture mechanics; crack growth depends on stress intensity factors.
• Material Toughness & Fracture Resistance:
  • High toughness materials can absorb more energy before fracturing.
  • Fracture toughness is critical in aerospace to prevent catastrophic failure.
• Failure in Composite Materials:
  • Often involves delamination, fiber breakage, or matrix cracking.
  • Anisotropic properties require specialized failure models.
• Fatigue & Creep:
  • Cyclic loading can cause failure at stresses below static strength (fatigue).
  • Sustained high temperature loading leads to creep failure over time.
• Corrosion & Environmental Effects:
  • Chemical degradation weakens materials, increasing failure risk.
  • Protective measures (coatings, anodizing) are essential.

💡 Key Takeaway

Failure theories provide essential frameworks to predict and prevent material and structural failure, especially in aerospace applications where safety and reliability are paramount. Understanding the failure mechanisms and criteria helps in designing structures that can withstand complex loading and environmental conditions without catastrophic failure.

📖 10. Design & Structural Optimization

🔑 Key Concepts & Definitions

• Structural Optimization: The process of designing structures to achieve the best performance according to specific criteria (e.g., minimum weight, maximum strength) while satisfying constraints such as material properties and load conditions.

• Material Properties: Characteristics that define a material's behavior under various loads, including strength, ductility, toughness, elasticity, stiffness, plasticity, fatigue resistance, and corrosion resistance.

• Elasticity: The ability of a material to return to its original shape after deformation when the applied load is removed.

• Structural Instability: A failure mode where a structure experiences sudden and large deformations under load, such as buckling, often due to inadequate stiffness or strength.

• Load Types: External forces acting on a structure, classified into:

  • Ground Loads: Forces during taxi, landing, or towing.
  • Air Loads: Aerodynamic forces during flight, including lift, drag, and moments.

• Material Selection Criteria: Factors influencing choice of materials for aircraft structures:

  • Strength-to-weight ratio
  • Stiffness
  • Toughness
  • Corrosion and fatigue resistance
  • Ease of fabrication
  • Cost and availability

📝 Essential Points

• Design Goals: Achieve optimal structural performance by balancing strength, weight, and durability through material selection and geometric configuration.

• Material Trade-offs: Improving one property (e.g., strength) often compromises others (e.g., ductility or corrosion resistance). Engineers must optimize these trade-offs based on application.

• Optimization Techniques: Use energy methods, finite element analysis, and iterative design to refine structural components for minimal weight and maximal load-carrying capacity.

• Structural Stability: Critical to prevent buckling and torsional failures, especially in thin-walled components like fuselage skins and wing structures.

• Load Path Optimization: Ensuring efficient load transfer through structural elements (frames, stringers, spars, ribs) minimizes material use and enhances safety.

• Material and Structural Innovations: Adoption of advanced composites (fiber-reinforced plastics) and optimized geometries (e.g., torsion-box wings) significantly reduce weight and improve performance.

• Design for Manufacturability: Structural optimization must consider ease of fabrication, inspection, and maintenance, especially in complex geometries.

💡 Key Takeaway

Structural optimization in aerospace engineering involves selecting and designing materials and geometries that maximize strength and durability while minimizing weight, ensuring safety and efficiency through advanced analysis and innovative materials.

📊 Synthesis Tables

Aspect	Elasticity & Basic Principles	Material Properties & Failure
Core Focus	Reversible deformation, elastic behavior	Ductility, strength, toughness, brittleness
Key Properties	Elasticity, ductility, toughness, fatigue	Ductility, strength, toughness, brittleness
Failure Modes	Fracture, fatigue, corrosion	Fracture, fatigue cracks, corrosion
Material Types	Metals, composites, alloys	Aluminum, titanium, steel, composites
Application Emphasis	Material selection based on elasticity and failure modes	Material selection balancing ductility, strength, fatigue resistance

Aspect	Structural Analysis & Loads	Material Selection & Properties
Core Focus	External forces, load paths, structural elements	Mechanical properties, weight, corrosion, cost
Key Concepts	Load types, load transfer, load distribution	Material strength, ductility, fatigue, corrosion resistance
Structural Components	Fuselage, wings, tail, landing gear	Metals, composites, alloys, their properties
Design Considerations	Load capacity, safety margins, reinforcement	Material compatibility, environmental resistance

⚠️ Common Pitfalls & Confusions

1. Confusing elasticity with plasticity—assuming elastic behavior implies no permanent deformation, which is incorrect for plastic materials.
2. Overlooking brittle failure signs—assuming all materials show warning signs before failure.
3. Misjudging fatigue life—assuming static strength tests suffice; fatigue involves cyclic loading effects.
4. Ignoring corrosion effects—assuming materials are corrosion-resistant when they may degrade over time.
5. Confusing toughness with strength—toughness involves energy absorption, not just maximum stress.
6. Misapplying material properties—using steel properties for aluminum components or vice versa.
7. Overlooking load transfer paths—failing to ensure load paths are designed to prevent stress concentrations and failure.

✅ Exam Checklist

• Define elasticity, ductility, strength, toughness, brittleness, and fatigue.
• Explain the importance of material selection based on mechanical properties and environmental factors.
• Describe common failure modes: fracture, fatigue, corrosion.
• Identify key material properties of aluminum alloys, titanium alloys, steel, and composites.
• Differentiate between elastic and plastic behavior, including elastoplasticity.
• Understand the effects of cyclic loading and fatigue life considerations.
• Recognize the role of non-destructive testing (NDT) in detecting hidden damages.
• Outline the types of loads acting on aircraft structures: static, dynamic, pressurization, maneuvering.
• Describe load transfer mechanisms and load paths in aircraft structures.
• Identify primary structural elements: fuselage, wings, tail, landing gear, and their functions.
• Understand the principles of finite element discretization for structural analysis.
• Summarize fracture and failure theories: Griffith, von Mises, maximum shear stress.
• Recognize the importance of structural optimization in design for weight, strength, and safety.