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ABSTRACT

“Material Selection for Smartphone Body Shell”

By Muhd Arshad Hassni, Bill Kyung Seok Baik, Muhammad Harith Mohd Fauzi,Jaehyuk Daniel Shim

The main goal in manufacturing a smartphone body shell relates to the phone’s durability,

performance and design. In terms of performance, the phone should be fully functional; choosing a

material that does not hinder with signal reception. Since every smartphone must maintain its

performance, the phone’s shell must play a key role in sustaining its functionality over time. This leads to

the importance of a durable shell, as our goal is to ensure that the device becomes capable of lasting

over time in terms of both its performance and appearance. Lasting through minor physical damage,

keeping the inside of the phone safe, and keeping the device reasonably compact and light are vital for

the current market.

Many resources exist in regards to the aspect of materials selection offering great potential to

significantly modify and optimize the current design of the smartphone shell. Some key characteristics

that we will be aiming to modify include the weight, stiffness and strength that the shell exhibits.

This report will explore a number of sequential steps through the material selection process that

is going to be used or considered in determining the best material candidates in designing the

smartphone shell. Through understanding the parameters which affect the performance of the shell,

important information has been collected and analyzed. This information will contribute to the process of

designing the smartphone shell thus affecting the materials selection. Therefore, by taking all of these into

account, this report is aiming to find the most suitable material that will optimize the functionality,

performance and durability of a smartphone body shell.

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1.0 INTRODUCTION

The purpose of this report is to investigate the best material that can be used for the smartphone

shell. This deduction is primarily based on our Material Engineering courses, including library and

internet research.

Advances in technology and the discovery of new materials have enabled researchers to create

new materials that perform better than existing materials. There are wide range of materials, some of

which make them viable candidates for use in the shell of the smartphone. There is always room for

improvement as the purpose of new development of better design and material used is to serve a better

performance of both the smartphone and its users.

First, the background history of the smartphone shell will be presented. This section will provide

a look into the evolution of the smartphone shell’s design. A section of design analysis is also included

regarding the conditions that must be met with the design of the new shell. Some attributes will have to

stay the same while others require improvements on ubiquitous problems that are prevalent in the widely

accepted standard for smartphone shell today. In regards to improvement of the current design, the

materials utilized for the shell of the smartphone in today’s market will be analyzed.

A free body diagram is provided for a better understanding of this concept. Material index will

be derived based on our desired material properties that we would like to optimize. From here, a

material will be selected from a list of material candidates that satisfies our design constraints. Next, we

will discuss about shape factors in order to determine the most appropriate shape for our selected

material in designing the smartphone shell. Finally, we are going to compare different processes in order

to select the ideal manufacturing route that both suits our design and minimize costs.

2.0 HISTORY

The first smartphone was introduced in 1990s produced by IBM. From its day of birth until

today, a number of design evolutions along with developments have occurred with the purpose to give a

better performance along with a better user experience. At the same time, the mechanical functions of

the smartphone shell also becoming more important. Different materials have been used throughout the

time in designing the shell in order to meet current design requirements. From plastic in the early days, it

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was developed through research to produce a stiff and light material known as polycarbonate that is

widely used currently by Samsung smartphone. On the other hand, stainless steel and aluminum alloy

have also become the choice of producers such as Apple in designing their smartphone(iPhone) shell

due to their unique properties. This shows that material selection plays an important role in designing the

smartphone shell in producing a smartphone with the best quality.

3.0 DESIGN ANALYSIS

This design strives not to change the fundamental principles of the object, but rather serves as an

update of incremental performance advancements. In regards to the shell of the smartphone which we

seek to optimize, there are several parameters that must be considered that will allow us to identify the

bounds within our specified designing process. Though it would be possible to come up with hundreds

of disorganized suggestions for the specification of the shell in consideration, we will be taking a

systematical approach by clearly and concisely identifying goals and constraints that are associated with

the design of the shell.

3.1 Free Body Diagram

Figure 1. Smartphone shell in bending

The free body diagram shows a situation where a smartphone shell is in bending situation. From

the magnified figure, we can see tension and compression situation that happen in bending. Therefore,

the material that we are going to use for the shell must be able to withstand these forces in order to

maintain the functionality of the smartphone.

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3.2 Design Constraints

The goal of the project is to optimize the shell of a smartphone in regards to its performance in

everyday use. Because there are a large quantity of resources to work with in regards to the aspect of

materials selection, there is much potential to significant modification and thus optimizing the current

design of the smartphone shell. Some key characteristics that we will be aiming to modify include the

weight, stiffness, and strength that the shell exhibits.

There is a lot to be desired in regards to overall performance. One factor we must consider is

thermal conductivity. In designing the smartphone shell, it would be reasonable to narrow down a

material that has a high thermal conductivity so that the body of the material does allow heat to flow

freely and thus prevent damage towards other components of the smartphone.

It is also important to consider the elasticity of the material that we will be using. We want to

choose a material with high toughness so that the material will not easily fracture, as such a mode of

failure would most likely affect the functionality of the smartphone especially if the phone is dropped. If

the material dents elastically on the other hand, this should be tolerable as the shape of the design should

only morph slightly and thus prevent any damage from being inflicted to inner components.

In designing a smartphone shell, we must also consider a situation where the shell will most likely

experience most of the time: bending. The compression and tension which happen in bending can affect

the functionality of the phone and might as well causes the phone to break easily. Therefore, in

encountering this problem, a stiff material should be selected in designing the smartphone shell so that

the shell does not bend easily thus preserve the phone in good condition.

In regards to the optimization of the shell’s performance, we should consider that a lighter

design will most likely be more favorable to users. This is because people nowadays tend to depend on

their smartphones more than ever and it is the device that they have in their hands everywhere they go.

Therefore, it is more convenient to bring a lighter device instead of having a heavy piece of technology in

their pocket.

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4.0 MATERIALS SELECTION

We will start our material selection process by translating our design needs discussed above to

function statements. We break down our design needs into function, objective, constraints, and free

variable statements for a systematical approach. Then we will utilize the material indices and material

property charts to screen out the best candidates.

4.1 Function

The function of the smartphone shell is to protect the core system of a smartphone; therefore,

the shell must be an elastic beam that can resist fracture due to external energy and creep over time. The

most significant function of the smartphone shell is not to exceed the elastic limit of the shell’s material

because the inner components of the phone cannot be protected anymore once the shell is plastically

deformed. For this reason, the beam has to be elastic so that the shell can absorb certain amount of

kinetic energy when the phone is dropped; in other words, the shell has to have the ability to return to its

original shape when the beam absorbs energy.

4.2 Objective

Our objective is to minimize the mass of the smartphone shell. This might be inconsistent with

our function of the smartphone shell; however, our group agreed that the toughness of the smartphone

does not need to be maximized since a phone will almost never experience extremely high energy.

Rather, we are looking to optimize the toughness of the shell because the shell should have some

degrees of toughness as phones are normally used in everyday life, not in extreme environments. This is

one of the main reasons why we decided to minimize the mass since high toughness often requires high

density that would make a phone too heavy for a user to carry. This leads to our main reason:

convenience. As the name of the product, smartphone, implies, the phone has to carry as many

functions as possible without weight of the phone disturbing the users’ comfort. In summary, the ideal

material for smartphone would have some resistance to fracture with the minimum weight.

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4.3 Constraints

Stiffness: High stiffness is required as to prevent major deformation of the phone in any real life

circumstance such as the phone being dropped from a user’s hand.

Elastic limit: Yield stress is the limit where the deformation caused by exerted force can return

to its original state. Since the plastic deformation of the smartphone shell would not fully

function, it is important for the shell to have high yield stress.

Thermal conductivity: Insulating material would not allow heat from inner components to

dissipate therefore resulting in overheating of the phone. However, good thermal conductivity

would also cause overheating from outer environments such as sun. Moderate thermal

conductivity of the shell would prevent the phone from overheating from both environment and

inner components.

Cost: The cost of the material used for the phone’s shell must be at a reasonable price and be

kept as low as possible. However, we are not going to find materials index for cost as it should

be dealt as multiple objectives. We are going to discuss cost in process selection part.

4.4 Free Variables Materials

Cross sectional area

Figure 2 Solid rectangular beam4.5 Material Index

Now that we have our constraints listed in 4.3, we can relate our objective with the constraints

to find the material indices to screen out the best material for a smartphone shell. We are going to use

yield stress for hardness, Young’s modulus for stiffness, and thermal conductivity as those three

properties are the main constraints that involves protection of the inner components of a smartphone. in

addition, due to the complexity of actual smartphone case’s geometry, we simplified its geometry to a

square beam. Square beam is suitable cross sectional area as most of the smartphone are mostly

rectangular.

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We are going to be using the equation for bending since bending is the most common

deformation for smartphone shell. Figure 3 illustrates how beam in bending is related to smartphone’s

deformation: 1 is the finger we use to click the smartphone and 2 and 3 acts as the supports. This also is

the case for dropping a phone; in the case of a drop, 1 would be the weight of the phone, and 2 and 3

would be the force due to the ground when the phone hits the ground.

Figure 3. Beam in bending

4.6 Derivation of Materials Indices

Derivation here is only a brief derivation. For the full derivation, refer to the appendix attached at

the back of this report. The variable are specified below:

m = mass; b = width; h = height; L = length; S = stiffness; F = Force due to bending;E = Young modulus; I = second moment of area; = density; = deformationρ δ

Material Index for Stiffness

Objective Equation: ALm = ρ

Constraints Equation: Deformation = Moment of Inertias = δF FL3

48EI I = A212

By rearranging the four equations above, and using area A as free variable, our objective equation

becomes,

( ) m = ρ 4ESL3 2

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therefore our material index becomes

M = ρE21

since we always want to maximize the material index, and our objective is to minimize the mass, we use

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the reciprocal of M. Thus our final material index for stiffness is with free variable “b” is

1M = ρ

E21

Material Index for Yield Stress

Since there is only one objective, the objective equation is going to be same for all the material

indices; therefore, all the equations that are referred as objective is the objective equation in the material

index for stiffness.

Constraint Equation: or σ = AF A = σ

F

By rearranging and combining the objective equation and constraint equation, the objective equation

becomes

L( ) m = F ρσ

then our material index for yield stress is

1M = ρ

σ

Material Index for Thermal Conductivity

Constraint Equation: − Q = λ tΔT

by rearranging and combining the objective and constraint equation using “A” as our free variable,

L m = ρ −( λ QΔT) 21

then our material index for thermal conductivity is

1M = 1

ρλ21

4.7 Material Property Charts and Screening

Now that we have material indices for our constraints, we are going to screen out materials that

has highest material indices therefore selecting the materials with the best performances for each

constraints.

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Chart 1. Young’s Modulus against density

Chart 1 relates Young’s modulus and density. The slope of the line is 2 according to the material index with free variable A(refer to material index for stiffness and appendix for slope). Candidates: Bamboo, CFRP, Rigid Polymer Foam (LD), Silicon Carbide, Wood (typical along grain)

Chart 2. Yield Strength against Density

Chart 2 relates yield strength and density. The slope of the line is 1 according to the material index with

free variable A (refer to material index for yield stress and appendix for slope) Candidates: CFRP,

Low Alloy Steel, Magnesium Alloys, Silicon Carbide, and Titanium Alloys

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Chart 3. Thermal conductivity against density

Chart 3 relates thermal conductivity and density. The slope of the line is ­1/2 according to our material

index for thermal conductivity (refer to material index for thermal conductivity and appendix).

Candidates: Copper,Gold, Silver, Tungsten Alloys, Tungsten Carbides

4.8 Selection from Initial Screening

Utilizing the material property charts illustrated above to screen out the candidates for

smartphone shell, we are taking any materials that were selected twice or more in three screenings

performed. We concluded that the possible candidate materials are Silicon Carbide and CFRP. On the

one hand, CFRP may meet stiffness and yield stress constraints, but it is far away from the material

index line for thermal conductivity. On the other hand, even though Silicon Carbide was not a candidate

material in thermal conductivity screening, it is fairly close to the material index line (refer to Chart 3)

and it satisfies stiffness and yield stress constraints. For this reason, we have selected, at this stage,

Silicon Carbide to be the best material for smartphone shell.

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5.0 SHAPE OPTIMIZATION

According to Ashby (2011), shape can be utilized “to increase the mechanical efficiency of a

material. which means that the section uses as little material as possible. Shape selection in design refers

to the selection on the cross­sectional shape in the form of tie or beam or shaft or column”(p.244). Our

group has agreed that the shell must be an elastic beam that can resist fracture due to the external energy

and creep over time.

5.1 Effect of Shape on Design

If we look at the existing design, smartphone manufacturers give their best to get the proper and

well­designed shape based on market demand. Some customers consider the mass of the smartphone

to be the most important, the lighter the phone, the more convenient the phone is. However, some of the

consumers would prefer smartphones made from high quality material. Manufacturing higher quality

products requires high cost thus having the ideal shape is essential to minimize the amount of material

used and definitely minimize our production cost.

5.2 Existing Design

For the past decade, technology has evolved in many different aspects including the

improvement on the shape of the material. As we know that, there is a trade­off between mass and the

performance of the smartphone. We can compare Samsung Galaxy II (SII) to Samsung Galaxy III

(SIII). Both smartphone models are made of polycarbonate, which exhibits a brittle fracture when the

material ( polycarbonate) is dropped with a very high speed. According to Gaymans, “brittle fracture

occurs on polycarbonate if the deformation rates are increased”(2000). For example, if we drop the

smartphone from the second floor of a building, the event will cause a large force when it hits the ground

due to the higher rate of deformation and causes brittle fracture.

Probability of brittle fracture can be reduced if we lower the stress concentration factor of the

material. If we compare both smartphones, SIII(133g) is heavier than SII(116g) by 17g but is more

resistance to deformation and crack propagation due to its round corners and curved edges (refer

Figure 8 in appendix). In a simple way, SIII has demonstrated a lower stress concentration factor due

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to a larger radius of the curvature of the crack tip formed. According to Callister, “stress concentration

factor is defined as the ratio of the maximum stress to the magnitude of the nominal applied

stress”(p.243).

The formula : = 2 as a is the length of the surface crack and is the radius of K t = σ°σm [aρt]

1/2 pt

curvature of the crack tip.

Under a brittle condition, the polycarbonate will undergo fracture if the shell’s material has a

very large stress concentration factor because of large stress amplification. Therefore, Samsung has

changed the shape from a rectangular corner to the curved corners to get a large value for which ρtlowered the stress concentration factor. But due to the change in shape, extra amount of material has

been added to accommodate the design shape for SIII. Therefore, it increases the mass and definitely

the phone’s production cost.

5.3 Shape Factors and Material Indices

Shape factor is the measure of the efficiency of the material usage. Recalling back, our group

has agreed that the smartphone acts as an elastic beam in which the design constraints from are the

stiffness and yield strength. Therefore, the beam must carry bending moments and our task is to

minimize the bending moment by having a proper shape. To do that, we need to obtain the correct

shape factor, which is represented by the ratio of the stiffness of the shaped section to the neutral

reference shape. Therefore, we make an analysis on the square beam and I­beam (refer to the

appendix). The best shape obtained in from previous analysis is the square beam.

Objective equation Constraint equation

Equation of Mass (i) m = (bh)Lρ

(ii) = 1m ρ

(Eϕ )eB1/3

( )( )4bSL3 −1/3 1

bL

(iii) S = = (stiffness equation)δ F FL3

48EI

(iv) I = ( the equation of I )(v) (deflection equation)δ = 12FL3

48Eϕ bheB

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(vi) S = ( new stiffness equation)L34Eϕ bhe

B3

(vii) h = (taking h as free variable) [ SL34Eϕ beB ]

−1/3

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Assuming the materials is silicon carbideThe amount of mass used for the square beam (h as the free variable) is 2.7*10^(­3) kg

The table above describes the derivation of the objective equation (i) as the function of density,

section area and length. From the table, we have taken the stiffness as the design constraint The

constraint equation is represented by equation (iii). Next, the second moment of area which is a variable

in the stiffness equation is defined as the function of the shape factor by equation (iv). Derivation has

been made and we take h as the free variable in equation (vii). Finally, we substitute the equation (vii)

into the objective equation (i) and get the new objective equation (ii).

Our group has agreed that the square beam is the optimal shape for our design as the mass for

the beam made out of Silicon Carbide is a reasonable mass(2.7*10^(­3)kg). In contrast, I­beam shape

has given us an unreasonable mass of 6.6*10^(­4) kg. If we pick I­beam as our design shape, the

design would be less stiff and there would be more deflection due to the bending.

5.4 Limiting Factor

However, when we consider the shape factor, there are some limitations that exist within the

design.The first is the empirical limit. If we look at the shape factor of the square beam, the shape factor

is equivalent to the ratio of the second moment of area to the section area. Based on the objective

equation, we have seen that, mass minimization requires us to maximize the shape factor.Theoretically,

we will take the second moment of area to be infinity and the section area to be as small as possible.

However, it is impossible for that kind of design. Therefore, it limits the numerical value of our shape

factor. Shape factor is represented by the slope of the log­log graph in the material chart below (

obtained from CES) : = (refer to the appendix).ϕeB A12I

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Chart 4. Second moment of area against section area

The upper limit for the shape efficiency are important. They are central to the design of

structures that are light or for which, for other reasons(cost), the material content should be minimized.

In addition to that, when efficient shapes can be fabricated, the limits of the efficiency are set by the

competition between failure modes. For this design, we just consider the bending as the failure mode

even we have the other mode of failure like buckling. The shape factor avoid generalized buckling in

compression can only made be increased by a certain amount because further increasing the shape

factor leads to the structure becoming unstable for localized buckling.

6.0 PROCESS SELECTION

Now that we performed our overall material selection, we will examine possible processing

techniques and come up with one process that is most suitable for our design. Previous analysis proved

that silicon carbide (SiC) with a square cross sectional shape is most suitable for our design of a

smartphone shell. Taking this into account, we will take the process selection approach to screen out

and rank the different processes accordingly. One type of process for each of the three manufacturing

steps (shaping, joining and finishing) will be needed. The screening process will be mainly taken through

the usage of process selection charts by Ashby and the CES software will help us the rank the

processes.

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6.1 Silicon Carbide

Silicon carbide (SiC, carborundum) is classified as a technical ceramic and is made by fusing

sand and coke (CES). It is a very hard, stiff material and works in very high temperature ranges. It is

highly resistant to corrosion and has excellent durability in almost any circumstance. Silicon carbide has

a density range of 3100 to 3210 kg/m3 at a price of roughly 14.76 USD/kg to 21.06 USD/kg.

6.2 Process Requirements

Before initial screening of the many processes, we should take into consideration exactly what

requirements should be met during processing. In the shaping process, we will aim to design a solid

square cross sectional shape as determined earlier through the use of shape factors. During the joining

process, it is crucial to regard which individual process will best keep the smartphone intact firmly

together when it faces damage. Finally, the finishing process will be essential to produce a smooth,

attractive surface for the smartphone to gain consumers’ interest.

The primary objective for process selection is to minimize the cost as much as possible. This is

an obvious choice since no manufacturer wants to inflate costs in processing especially. Another

objective is considering which process provides best compatibility and be as efficient as possible.

6.3 Shaping Process

Figure 4 consists of a process compatibility chart in which all types of materials are labeled and

recorded if a certain process can be made possible with a chosen material. In our case, we are only

going to consider silicon carbide which is a ceramic. This chart shows us that our immediate process

candidates for shaping are powder methods, electro­machining and conventional shaping. All three

processes are able to generate our proposed shape (square beam shape) at a wide range of mass,

giving us some insured flexibility.

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Figure 4. Shaping process selection

Subsequently, we will analyze a process­section thickness chart (Figure 5). This chart shows all

the different possible thickness ranges that individual processes can produce. We will arbitrarily set a

safe section thickness range of 7­10 mm and this is reasonable for a thickness of a modern smartphone.

As indicated by the chart, electro­machining cannot produce a section thickness of 10 mm it lies a little

short of it. Therefore, at this point we will eliminate electro­machining as a possible process solution.

This leaves conventional machining and powder methods as our candidates that will be analyzed further.

Figure 5. process­section thickness chart

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6.4 Ranking the Shaping Process

Within the numerous different methods of conventional machining and powder methods, we will

narrow it down to three possible choices. The reason for this was that not all methods were compatible

or could operate at a reasonable cost. The three methods we believe are best suitable is circular sawing

(conventional machining), powder injection molding (powder methods), and pressing and sintering

(powder methods). From these 3 methods, we will then determine which one is the most efficient in

terms of cost and production for our smartphone shell design.

Circular sawing: a rotating circular blade is used to make contact and shape the material. The

blade can be used horizontally, vertically or in an inclined angle to provide great precision and smooth

finish on the surfaces. It provides compatibility with both small and large material masses as it is

commonly used in many engineering applications (specifications in appendix).

Powder injection molding: a process in which ceramic powder and a thermoplastic binder

injected together under a specific pressure into heated molds on standard injection molding machines

(specifications in appendix).

Pressing and sintering: loose powder packed in a shaped ceramic is sintered at almost 2/3 of

the powder’s melting temperature. Powder is first compressed in a cold die to give it strength so that it

can be sintered as a free­standing body. Hot pressing is used for better densification, strength and

ductility of the final material (specifications in appendix).

As we are aiming to identify the process with the lowest cost when the smartphone case is in

mass production, we are going to use process cost model equation to compare the costs of our

candidate processes. The cost model indicates that, for mass production, pressing and sintering has

lower cost than powder injection and molding (more details in Appendix). Then the comparison

between circular sawing and pressing/sintering tells us that pressing/sintering is more applicable in our

case because of high production rate and reasonable size of batch rate and capital cost (refer to Table

1). aterial cost per unit mass C = m + Batch SizeFixed Tooling Cost + 1

Batch Rate∑i

1Overhead Costi

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Circular sawing Powder injection

molding

Pressing and

sintering

Tooling Cost Low High Medium

Equipment Cost Medium High Medium

Labour Intensity Medium Low Low

Capital Cost (not specified) $165 945­

$1 659 450

$58 125­ $331 890

Production rate (not specified) 40­ 360 /hr 120­ 1200 /hr

Economic batch size 1­ 10 000 000 100 000­ 10 000 000 5000­ 5 000 000

Table 1. Cost­process comparison

For circular sawing, the batch size range spans too long to the extent that capital cost and

production rate varies vastly. The labour intensity for circular sawing is highest among the three, which

means that although tooling cost is low the labour costs cannot be neglected. The powder injection

molding method is a rather quick, expensive production method. In this process, although labour

intensity may be low, the tooling cost is considerably high along with equipment cost. This means that

this process is going to take up money periodically and fail to meet our objective. Consequently, the

pressing and sintering method appears to be the ideal choice it provides a moderate cost range that is

fairly manageable.

At this point, it is safe to say that pressing and sintering is the most suitable for our smartphone

case processing method.

6.5 Joining Process

The next step is the joining process, here we will examine which process is compatible with

silicon carbide and choose the one that offers the best results. According to Figure 6, it is accurate to

state that adhesives and fasteners are the only possibilities in our design as silicon carbide is a ceramic.

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Figure 6. Joining process selection

Through usage of the CES software, we learned that the specific processes that are directly

compatible with ceramics are flexible adhesives, rigid adhesives and snap fit fasteners. Further details

and specifications of these methods can be found in the Appendix.

Through comparison, rigid adhesives appear to be the best choice. First of all, snap fit fasteners

work best with materials with large yields strains such as polymers. Although usage with ceramics may

work, it may not be the ideal selection as snap fit fasteners are mainly used for polymer parts or metal

casings. Although the usage of flexible adhesives could also be a fair choice, we believe that they are

mostly applied with metals and polymers mostly on large scale structures. Rigid adhesives do offer

larger ranges of materials that were frequently used, which includes ceramics. As referenced in the

appendix, they are constantly used in the electronic industry from recent past therefore it was an

attractive choice for rigid adhesives for our joining process.

6.6 Finishing process (surface treatment)

Today’s users demand fashionable and trendy cases for their phones, which is why we need to

consider finishing processes that can enhance the appearance of our smartphone case. At this stage of

our designing process, we can improve our design by introducing and applying appropriate surface

treatment to our material.

In our case, our objectives for final processing are to improve the fracture toughness and

enhance the appearance. Ashby proposes a few of common final processes such as heat treatment,

quenching and coating. Polymer powder coating/spraying is one of the suitable options for our final

processing treatment since polymer coating would enable us to colour the surface for an attractive look.

Not only that, the polymeric surface would prevent surface cracks of SiC from propagating thus

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improving our drawback of fracture toughness.

There are three types of polymer coating: polymer electrostatic spray, flame spraying, and

fluidized­bed coating. All polymer coatings are applicable to our smartphone case because none of them

are toxic, or has any negative effect on environment and all of them enhances the performance of the

smartphone case. However, electrostatic spray stands out as our top candidate for surface treatment

due to its desired properties: good surface hardness, smooth surface, medium equipment cost, and low

relative tooling cost. Those physical properties would meet our finishing process objectives to improve

the fracture toughness and to improve the appearance.

7.0 CONCLUSION

Throughout this report, our group demonstrated how silicon carbide is the best material for our

design of a smartphone shell. Although ceramics are not commonly used in today’s smartphones, we

attempted to introduce several good qualities that ceramics possess and should be considered in future

smartphone designs. We were able to prove that silicon carbide satisfies all of our needs for this design

through various analysis and comparisons with other materials. This material provides the ideal stiffness

to resist plastic deformation and maximizes our material indices for optimal performance. After that, we

observed that a solid square cross section is the most efficient through shape factor analysis. For the

manufacturing process, we undertook various screening and ranking of the numerous processes and

methods that were available to us. From these we were able to determine that shaping was to be done

with the pressing and sintering method, using rigid adhesives for joining the material together, and

polymer electrostatic spray for surface treatment. Using all sequential analysis shown in this report, we

are now prepared to take the next step to material development in the smartphone industry.