Material Selection for Drones (UAV), Degradation and Thermal Stress Calculations PDF

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Program: BSc. Aeronautical EngineeringName ID: Idris Ahmed MalikEAU ID: 20181141558Material Science & EngineeringInstructor Name: Mr. Ajit YesodharanDue Date: 27-May-Topic: Assignment (Project)Abstract:The lightweight and strong materials that should be used in manufacturing of Unmanned Aeri...

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Program: BSc. Aeronautical Engineering Name ID: Idris Ahmed Malik EAU ID: 20181141558

Material Science & Engineering

Instructor Name: Mr. Ajit Yesodharan

Due Date: 27-May-2020

Topic: Assignment (Project)

Abstract: The lightweight and strong materials that should be used in manufacturing of Unmanned Aerial Vehicle (UAV) or Drone are included in this study. Currently, the technology development of the UAV is becoming more creative and advance. The mapping and observation process from the UAV will be efficient and cost-effective. The process of mapping and monitoring requires high UAV durability, for this reason, development of lightweight and rigid materials is required. Lightweight technology is very effective in UAV technology. Composite materials have many advantages in aerodynamics. The composite materials are made of fiberglass and resin, and this material must be used in parts not loaded with excessive pressure. The aviation industry uses fiberglass composites widely because of the hardness, strength, and toughness of the composite. This study was performed by selecting different materials that are suitable especially for drones. The first step was selecting the perfect material from many options available nowadays. The next step involved the advantages and disadvantages of the selected materials for better understanding and why a specific material may be more suitable, among others. In later steps, structural and mechanical properties of these selected materials are discussed in detail. The purpose of defining these properties was to differentiate the selected materials from other options and why these materials are more appropriate for the specific job. In the second task, the possible degradation, and the causes of degradation of these selected materials was conferred. Lastly, the thermal stress was calculated for the chosen material that must be used in control rods of the drone.

Task 1: Drones A Drone is a type of unmanned aerial vehicle (UAV) or known as unmanned aerial systems (UAS). The Drone is an airplane or remote-controlled robot or aircraft with software-controlled flight plans in their embedded systems, which work in conjunction with onboard and GPS sensors. [ CITATION Mar16 \l 1033 ]

UAV : Source

Drone : Source

Types of Drones: Drones can be classified on a different basis. They are based on 'use' such as Drones for Photography, Drones for a Mapping, Drones for Surveillance etc. However, the best differentiation of drones can be done based on aerial platforms. Based on the type of aerial platform used, there are 4 major types of drones: [CITATION Cir \l 1033 ] 1. Multi Rotor Drones 2. Fixed Wing Drones 3. Single Rotor Helicopter 4. Fixed Wing Hybrid VTOL (Vertical Takeoff and Landing)

Components of Drones: The main components that are considered for the drone manufacturing would be: 

Fuselage



Wings



Empennage (Tail)



Control Rods



Landing Gear



Tires



Electrical Cables



Propeller

Materials Selection for Drones: Drones are complex devices that are made up of different materials that work together. Each element performs a different function, so different factors are evident when selecting materials for each component. However, for each drone piece, the density of the material should be considered to minimize weight and maximize performance. [ CITATION Mat19 \l 1033 ] Top materials used in drones are: 

Carbon fiber – reinforced composites (CRFCs)



Thermoset Polymers or Thermoplastics such as polyester, nylon, polystyrene etc.



Aluminum



Lithium ion Batteries

Fuselage

Fuselage Components and Material Selection:

UAV Fuselage Design : Source The fuselage consists of two main parts which are frame and skin of the fuselage. Each of these components requires different material for fabrication. Equipment of each part must be considered with great meticulous.

Fuselage: Source

Materials for Fuselage Frame: The selected material for fuselage frame will be considered for a few things such as the manufacturability, cost, power, weight, cost of production, and easily available in the market. Following materials are considered for fuselage frame:



Material Options:



• Stainless steel

• Iron

• Carbon Rod

•Aluminum

• Balsa Wood

• CFRPs

Material Selected:  Balsa Wood

 Advantages and Disadvantages of Selected Material:

Advantages of Balsa Wood Balsa Wood has the lightest weight





Disadvantage of Balsa Wood The drawback of using Balsa Wood in

among aluminum, carbon rods, stainless

Fuselage frame is that the strength of

steel, and iron.

balsa wood is not strong as compared to



It is cheapest as compared to others.

other materials.



Balsa wood is comparatively softer than other materials therefore the manufacturing cost is low.



Since it is softer, the manufacturability is better than others

Material for Fuselage Skin: UAV’s fuselage skin must be low in weight but must be tough and strong enough to protect fuselage frame. The cost of maintenance for the skin must be low. Also, the skin should not have corrosion and cracking due to fatigue. It should be easily produced in an efficient manner during its production. Following materials are considered for fuselage skin:



Material Options: • Fiber Glass Reinforced Plastic (FGRPs) • Carbon Fiber Reinforced Polymer • Spectra Fiber (A super-fiber engineered for its lightweight strength, abrasion resistance and durability – designed by Honeywell)



Material Selected:

 Spectra Fiber

[ CITATION Spe18 \l 1033 ]

 Advantages and Disadvantages of Selected Material:



Advantages of Spectra Fiber Low weight



Disadvantage of Spectra Fiber Higher costs for maintenance



Excellent corrosion resistance



Limited shortages of established



High resistance to fatigue



Reducing machinery works



The ability to form composite and

inventions and designs 

Degradation of structural properties at high temperature or when wet

complex components 

The ability to move fiber reinforcement straps and durability



A very low thermal expansion that reduces operating problems in highspeed and high-altitude flights.

[ CITATION Bor04 \l 1033 ]

Wings Due to the high requirements of modern UAV components (low weight – high strength) composites material continues to be the most suitable choice. These materials are characterized by a slightly higher Young’s modulus compared to aluminum alloys also has low weight, twice of that Aluminum. [ CITATION Łuk15 \l 1033 ] Wings of unmanned aerial vehicle (UAV) require different airfoil shape, chords, thickness, span, dimensions, surface area and geometry according to the destination and altitude. Despite of difference, one specific material can be used to all types of UAVs

Drone Wings: Source

Material Selection for Wings:

 Polymer Matrix Composites

Source: 2015 WILEY

Through analyzing above table, Polymer Matrix Composites is selected among all other available composites due to the low-cost fabrication and attractive properties. The most common Polymer Matrix Composites include Vinyl ester, epoxy, phenol, and formaldehyde (PF), Polyamide and polypropylene (PP).  Advantages and Disadvantages of Selected Material:

Advantages of Polymer Matrix

Disadvantage of Polymer Matrix



Composites Low cost of fabrication



Composites Low thermal resistance



Low density



High coefficient of thermal



High strength



High stiffness



Delamination occurs more often



Corrosion resistance



Complex fabrication



Vibration damping ability



Internal delamination and cracks



When reinforced with continues fibers

make it difficult to inspect, hence

obtain higher mechanical properties

complicated inspection techniques

than conventional mechanical

for detection are required.

properties 

High strength to weight and stiffness to weight ratio



Ability to produce fabrics such as

expansion

plain weave, twill weave, satin weave, and unidirectional weave.

Empennage (Tail) The empennage is also known as tail assembly or tail of the UAV. It is used to provide the stability to whole aircraft or drones. It is equipped with vertical stabilizing surface (also known as Rudder) and horizontal stabilizing surfaces (also known as elevators). These stabilizers are called control surfaces and are used to control the yaw and pitch movements of the aircraft or UAVs.

Empennage : Source

Materials Selection for Empennage: Same materials are to be considered for empennage as in selection of Fuselage frame materials like Stainless steel, iron, carbon rod, aluminum, balsa wood, and CFRPs. Since, strong material is required for constant maneuverability, the selected material should be strong, light weight, cost effective and must have high strength to weight ratio. Following is the material selected for empennage or tail for the drone. 

Material Selected:  Balsa Wood

The advantages and drawbacks are already discussed in the above/previous section (fuselage frame)

Control Rods

The control rods are also called push rod assembly. These control rods provide the linkage to different components in the drone or unmanned aerial vehicle (UAV). But most importantly, these control rods are used to control flaps and throttles.

Materials Selection for Control Rods: There are some options that can be considered for perfect control rods: 1. UAV Grade Ball Links 2. Titanium Control Rods 3. Stainless Control Rods

Control Rods : Source



Material Selected: 

Titanium Control Rods

 Advantages and Disadvantages of Selected Material:

Advantages of Titanium Control Rods  Hybrid Configuration  

Disadvantage of Titanium Control Rods  Expensive than steel and brass

Designed for extreme environment



Manufacturing cost is high

and altitudes



Custom made – not easily available

Coefficient of thermal expansion is lower than others



No friction Issues at higher altitudes



Stronger tensile strength than

in the market

others

Landing Gear Landing gears are major part of any UAV. The landing gear provides the stable support for the aircraft resting on the ground. During the landing, it acts as a shock absorbent of mechanical structure to absorb and transfer these loads to the dynamic part of the UAV (fuselage) so that most of the impact forces are dissipated. Landing gears also act as brakes during movement of UAV on the runway. [ CITATION IJM15 \l 1033 ]

Landing Gear : Source

Material Selection of Landing Gear: For landing gear, different materials are available which can be used for their unique combination of properties. Material for landing gear must have following properties: High strength, long fatigue life, excellent resistance to oxidation, moderate density, fracture toughness, higher creep strength and excellent resistance to corrosion.[ CITATION Sci12 \l 1033 ] Material Options: Following are some options to consider: •Aluminum Alloys •Nickel Alloys

Material Selected:

•Steel Alloys

•Titanium Alloys

•Magnesium Alloys

 Titanium Alloy (10Al-2Fe-3V)

Source: Mechanical Properties of Titanium Alloy (10Al-2Fe-3V)

 Advantages and Disadvantages of Selected Material:



Advantages of Titanium Alloy High Strength

 



Corrosion Resistance



Has good mechanical properties and can be easily welded



Has specific applications in aerospace industry



Long fatigue life,



Excellent resistance to oxidation and corrosion



Moderate density; Higher fracture toughness; higher creep strength

Tires

Disadvantage of Titanium Alloy Expensive than other alloys Must be designed and manufactured for specific purposes

The main purpose of tires is to provide mobility on the ground. In addition, they help the shock strut by reducing the impact of landing and absorb much of the roughness of takeoff and provide grip for stopping. [ CITATION NAV02 \l 1033 ]

Drone Tires : Source

Material Selection of Tire: Since there are only two option available for tire selection. 1. Tube-less tires

2. Tube type Tires

Material Selected:  Tube-less tires

 Advantages and Disadvantages of Selected Material:



Advantages of Tube-less Tires No silly punctures

Disadvantage of Tube-less Tires  Difficult to fit



Ability to run at lower pressure



Not all punctures are fixable



Light Weight



Expensive



Less friction



More stability

Electrical Cables

Electrical cables act as a nervous system for drones. These are used to provide electric power and to control the movements of the UAVs. Wire size is usually measured in AWG (American Wire Gauge), the smaller the number, the larger it is. To minimize the weight of drone, it is important that smallest possible wires must be selected.

Electrical Cables for Drones : Source

Material Selection of Electrical Cables: 

Copper wire is selected for electrical cables with following specifications:  For Battery: 14AWG for powerful setup and 16AWG for light weight builds  For Motor: 18AWG for powerful setup and 20AWG for light weight builds  Signals between components / Low Current (under 1A): 28AWG

Unit Conversion Table (AWG - Ampere):

Propeller

Propellers are devices that convert rotational motion into vertical rotation. Drone propellers provide the aircraft/UAV with spinning movement and airflow, resulting in pressure differences between the upper and lower parts of the propeller. This speeds up the bulk of the air in one direction, giving it the ability to lift against gravity. [ CITATION UST19 \l 1033 ]

Drone Propeller : Source

Material Selection of Propeller: Material Options: Following are the two options to consider: •Plastic

•Carbon Fiber

Material Selected:  Carbon Fiber  Advantages and Disadvantages of Selected Material: Drone propeller blades are usually made mostly from plastic or carbon fiber. Plastic propellers are cheap and flexible, which allows them to produce a better impact. The increased durability of carbon fiber propellers, although it offers less rigidity, reduces vibrations thus improving the drone's flight performance and making it quiet. Carbon fiber is also lighter than plastic, allowing it to save weight.

Structural & Mechanical Properties of Selected Materials

Modulus

Tensile

of

Strength

Elasticity

(Yield)

3.71 GPA

11.6 MPa

9%

3 MPa

Wood

172 GPa

3000 MPa

2.9 – 3.6%

300 MPa

Composite

PMC

333 - 1226

410-1180

(Fibers)

MPa

MPA

18%

3.7 GPa

Composite

HCP

80-125

(alpha - α)

GPa

14%

54 MPa

Metal

9-10%

945 MPa

Selected

Structure

Material

(Type)

Balsa

Grains (A,

Wood Spectra

B, C-type) Laminated

Fiber Polymer

Structure

Matrix Composite s Titanium (Control Rods) Titanium

Fatigue Elongation

Limit

Material

(Strength)

434 MPa

BCC

Alloy (10Al-

Lattice

107-110

900-970

2Fe-3V)

Structure

GPa

MPa

Metallic Alloy

(beta - β) May vary Tube-less Tire

Monomers

2.5 GPa

85 MPa

~ 21-65%

with

Rubber

quality/Load / usage

Copper Wire

BCC / FCC

30 GPa

97 MPa

40 – 50%

60-80%

Metal Composite

Carbon Fiber

(when HCP

228 GPa

3.5 GPa

1.5%

N/A

combined with other materials)

Source: Data obtained from multiple online resources and calculations, (Values may vary)

Task 2:

Degradation

Degradation of Materials: Degradation is the deterioration of a material because of environmental reactions.[ CITATION Mac18 \l 1033 ] Types of Degradation: There are three main types of degradation: 1. Water Degradation

2. Land Degradation

3. Atmospheric Degradation

There is also chemical degradation because of chemical reactions. Degradation of Selected Materials: 

Balsa Wood Degradation of Balsa Wood:





Caused by: Fungi, insects, and water



Degradation: Erosion, cavitation, shrinkage and tunneling patterns of deterioration.

Spectra Fiber Degradation of Spectra Fiber: 

Caused by: Damages during production, exposure time, temperature, and humidity



Degradation: Flattening of fibers, reduction in load-bearing capacity and partial delamination.



Polymer Matrix Composites: Degradation of Polymer Matrix Composite: 

Caused by: Exposed to UV radiations, freezing temperature, water, and aging



Degradation: Corrosion, structure failure, reduction in durability, decrease in strength, and change in elastic constants.



Titanium (Control Rods): Degradation of Titanium: 

Caused by: Humid air, constant load and pressure, environmental location, bad design features



Degradation: Brittle cracking, fracture, and surface corrosion.