LAPTOP SCREENS
Figure 1: LCD screen in a Laptop and the different components
Description
According to PC Magazine Encyclopedia, many laptops, today use high-quality Liquid Crystal
Display (LCD) screens. A laptop screen also called a LCD screen displays an image generated by
the laptop video card. The image is converted to electric signals sent to the screen and are then
reconverted to graphics. An LCD screen works by breaking the picture down into dots and
recreating it. A backlight lamp (also known as cold cathode fluorescent lamp (CCFL) bulb), the
main source of light in any LCD screen, shines light through two sheets (usually plastic) with a
layer of liquid crystal between them. The sheets are polarized in a perpendicular manner, meaning
that it allows to pass light through a sheet if it has a set orientation. This manipulation comes from
the individual crystals which, in response to an electrical charge, can polarize light and, in turn,
cause it to pass through the outside sheet and become visible. The case housing the screen is made
of glass or plastic and protects the polarized sheets. LCDs are based on the principle of polarization
(blocking light) rather than producing it, hence the need for the backlight.
LCD screens are used display information and media in a variety of devices: fax machines, laptop
computer screens, answering machine call counters, scientific instruments, portable compact disc
players, digital clocks, watches and microwave ovens.
Manufacturing Process and Safety
A LCD consists of several components: display glass, drive electronics, control electronics,
mechanical package, and power supply. A LCD can either be a passive matrix (PMLCD) or an
active matrix (AMLCD). According to Jeff Tyson (2000), author of the website, How Stuff are
Made, the passive matrix LCD “has a grid of conductors with pixels located at each intersection
in the grid”. Electricity is applied to control the light of each pixel. On the other hand, an active
matrix, also known as a thin film transistor (TFT) display, has a transistor located at each pixel
intersection, requiring less current to control the luminance of a pixel. The manufacturing process
for AMLCDs, however, is much more difficult than that for passive matrix LCDs. An LCD with
a single imperfection is discarded. This makes them very expensive to manufacture. Inorder to
manufacture passive matrix LCDs, the surface and rear glass of the display is first polished,
washed, and coated with silicon dioxide (SiO2). A layer of indium tin oxide is applied to the glass
and allowed to volatize and etched into the desired pattern. Subsequently, a layer of long chain
polymer is then applied to allow the liquid crystals to align properly, followed by a sealing resin.
The spacers next are put into place, and the glass sandwich is filled with the liquid crystal material.
The assembly is allowed to age and then mounted to integrated circuits and drive assembly (Tyson,
2000). Glass breaking is a significant hazard in LCD manufacturing; cuts and lacerations may
occur. Additionally, the chemicals used in cleaning and manufacturing LCDs are poisonous and
are irritants to the skin (Lister, 2017).
Material
A LCD screen’s main component are liquid crystals. Liquid crystals are materials that are in
intermediate phases. Both liquid and solid properties are demonstrated by liquid crystals; flow
properties associated with liquids and ordering properties in solids. LCs have ordered structures
with molecules aligning parallel to each other and their maximum axis and thus exhibit
anisotropic properties (University of Alabama at Birmingham, 2003). This means that they
exhibit a variety of physical properties, such as dielectric constant e, refractive index n, magnetic
susceptibility c, conductivity s, and viscosity h, have different values in the direction parallel and
perpendicular to the molecular axis.
An LCD screen is based on the following criteria (HowStuffWorks):
 The ability to transmit and change polarize light as this will determine what orientation of
light is seen. It will be able create dark images on the screen.
 The structure of LCDs can be changed by electric current. The ability to be altered
predictably by electric current is one of the main reason LCs are used as it creates a way
as to control light passage.
 The ability to conduct electricity is important as it allows for the orientating of the materials
molecular axis which is the basis of LCD technology; allowing for the polarization of light,
just by the application of a voltage.
The LC materials used in current LCDs are highly developed mixtures of various compounds
tailored to meet the requirements of environmental stability, wide operating temperature range,
proper response to the applied electric field, high electrical resistivity for matrix addressing, and
fast response time (Sarma, 2000).
Most of the LC materials are organic compounds which consist of rod-shaped or disk-shaped
molecules. For display applications, LC materials with rod-shaped molecules are the most
commonly used. Depending on the temperature and particular nature of a substance, liquid
crystals can be in one of several distinct phases. The LC materials are broadly classified into
three types (phases) — smectic, nematic, and cholesteric — according to their molecular order.
The nematic phase is primarily used in LCD screens. One feature of liquid crystals is that they're
affected by electric current (anisotropic property). A particular sort of nematic liquid crystal,
called twisted nematics (TN), is naturally twisted. Applying an electric current to these liquid
crystals will untwist them to varying degrees, depending on the current's voltage. This is one
property that is controlled for LCs for use in LCDs (Tyson, 2000). A classic example of a
nematic LC material is p-azoxyanisole (PAA or C14H14N2O3) with a nematic phase in the range
of 117 to 136 °C. Another but older example of nematic LC is N-(p-methoxybenzylidene-pbutylaniline) (MBBA or C18H21NO) with a nematic phase in the range of 22 to 47 °C.
The thickness of the LCD cell is usually restricted to 5-25 micrometers. Because proper
thickness is crucial for cell operation and because spacers don't always achieve uniform
thickness.
BULLET PROOF VEST
Description
Bulletproof vests are modern light armor specifically designed to protect
the wearer's vital organs from injury caused by firearm projectiles.
Modern bulletproof vests consist of panels, a vest-shaped sheet of
Figure 2: Bulletproof Vest;
Curtesy of
http://kevlarbulletproofvest.
weebly.com
advanced plastics polymers that is composed of many layers of either
Kevlar or Dyneema® that is sealed together. Bulletproof vests are used to
reduce the impact of bullets on the body. Kevlar® is used to make vests, car tires, diving gloves,
cut resistant gloves, fireproof clothing, military helmets, panels and wings for fighter jets, and
the bodywork and petrol tank for Formula One racing cars (Ryan, 2011).
Manufacturing Process and Safety
In order to manufacture bulletproof vests, the polymer, poly-para-phenylene terephthalamide,
must first be produced through polymerization which results in a crystalline liquid with polymers
in the shape of rods. Kevlar is an aromatic polyamide. The synthesis of these polymers is done
through the nucleophilic acyl substition between a diamine and diacid, both substituted with a
phenyl group. It is then spun in to yarn, filament or fiber by extrusion through a spinneret (a
small metal plate full of tiny holes that looks like a shower head). The yarns are then further
woven into a sheet material that is bulletproof. The bulletproof panels, are cut into patterns and
extensive testing is required to identify the proper thickness of ballistic material. The level of
protection required determines the thickness of the final product. The cut and sewn layers of
ballistic material then need to be put into a protective envelope which is then heat sealed with
Kraton against water and humidity. The sealed cover is the basic ballistic panel that provides a
bulletproof vest with its bullet resistant qualities. The ballistic panels are then fitted into a
specially designed carrier. A carrier, plus ballistic panels together form the basic bullet resistant
vest (Body Armour News, 2010). The solvent that dissolves the polyamides is very toxic and
proper protective suits have to be worn when manufacturing Kevlar®.
In selecting materials for a bullet proof vest, the material must have:
 High strength to weight ratio- High-strength fabric liner acts as body armor, it absorbs
and diffuses the remaining portion of energy of the bullet and play the role of a buffer, so
as to reduce the non-penetrating injury. Theoretically, the higher the tensile strength, the
lesser the elongation ability of a strong material and its potential energy absorption
(Jiangsu Anhua Police Equipment Manufacturing Co.,Ltd, 2014).
 High modulus- High modulus in the material for the body armor does not allow excessive
deformation, so the inevitable fiber for body armor while having a high ability to resist
deformation (Dupont Inc., 2014).
 Toughness - The vest should be able to absorb the energy of the bullet and deform
plastically.
Bulletproof vests undergo many of the tests. The fiber manufacturer tests the fiber and yarn
tensile strength, and the fabric weavers test the tensile strength of the resultant cloth.
Kevlar® fiber and filament come in a variety of types, each with its own unique set of properties
and performance characteristics for different protection needs. Several grades of Kevlar are
available (Dupont Inc., 2014):
Kevlar K-29 – used in industrial applications, ballistic applications, ropes and cables, protective
apparel such as cut-resistant gloves, in life protection uses such as helmets, vehicular armoring,
and plates, as rubber reinforcement in tires & automotive hoses, asbestos replacement, brake
linings, and body/vehicle armor.
Kevlar K49 – High-modulus type used primarily in fiber optic cable, textile processing, plastic
reinforcement, ropes, cables, and composites for marine sporting goods and aerospace
applications.
Kevlar K100 – colored version of Kevlar, used in ropes and cables, tapes and strappings, gloves
and other protective apparel, and sporting goods.
Kevlar K119 – higher-elongation, flexible and more fatigue resistant yarn types found in
mechanical rubber goods, such as tires, automotive belts, and hoses.
Kevlar K129 – higher tenacity for ballistic applications,
Kevlar AP – 15% higher tensile strength than K-29, next-generation fiber that offers advanced
performance, value, and increased design flexibility in many applications.
Kevlar XP – lighter weight resin and KM2 plus fiber combination, used in motorcycle racing
gear, life protection accessories, ropes and cables, and high-pressure hoses used in the oil and gas
industry.
Kevlar KM2 – enhanced ballistic resistance for military armor applications.
Any ballistic pack made of several layers of material stitched together will retain moisture after
being saturated with water. When this happens the water acts as a lubricant, aiding a projectile to
penetrate the structure. For this reason, fabrics of Kevlar® used for ballistic vests are treated with
a water-repellent according to a procedure specially developed for ballistic fabrics of Kevlar®
(Kumar, 2016).
Although the specific details of the manufacturing of aramid fibers remain proprietary secrets, it
is believed that the processing route involves solution polycondensation of diamines and diacid
halides at low temperatures (near 0°C), resulting in the formation of aramid forming polyamides.
Low temperatures inhibit by product generation and promote linear polyamide formation,
allowing maximization of strength and high modulus (University of Alabama at Birmingham,
2003).
CRICKET BAT
A cricket bat is specialized piece of equipment used by batsmen in the
sport of cricket to hit the ball (Venkataramaiah, 2015). The bat consists of
a cane handle attached to a flat-fronted willow-wood blade. The shape of
the blade of a cricket bat is generally flat on the striking face and with a
ridge on the reverse (back) that has the most wood and is the section in
Figure 3: Cricket bat;
curtesy of
allroundercricket.com
which the ball is hit. The bat is traditionally made from willow wood,
specifically from a variety of White Willow called Cricket Bat Willow
(Salix alba var. caerulea), treated with raw (unboiled) linseed oil, which has the protective
function of maintaining the moisture levels in the wood and thus preventing cracks (Cricket Bats
Manufacturing Process, 2013).
This variety of willow is used as:
 It is very tough and durable as it can absorb the energy of the ball without fracturing and
be utilized repeatedly.
 It is shock-resistant, flexible and resistant to splintering not being significantly dented nor
splintering on the impact of a cricket ball at high speed.
 It is light in weight so that the batsman can wield the bat easily.
Manufacturing and Treatment
Bat manufacturing process is totally a manual skilled job and the perfect shape and size of bats is
totally depends on skill level of operator. However some companies use CNC lathes to shape
bats.
Whole trees are cut and then segmented into 28 inch (71 cm ) lengths with chainsaws. The
lengths are then divided into ‘clefts of required size, which is shaped roughly into bat shape. This
process is called riving. It is important that the correct side of the cleft is chosen as the face as
this is what will become the face of the finished bat. The “blade” as it is now known, then has
both ends waxed to prevent splitting and then air or kiln dried to the required moisture content.
Special care is needed when testing the moisture content to ensure that reasonable uniformity is
achieved (Cricket Bats Manufacturing Process, 2013).
The blades are pressed, so that the bat internal fibers come closer and provide strength so that bat
can withstand the impact caused by cricket ball. Pressing is an important operation as over
pressing can make bat surface hard.
After pressing, the handle is fit to the cricket bat. The handle is made from twine which increases
its flexibility and strength. After fitting the handle, the craftsman places the bat into vice and give
the final shape of cricket bat by removing the extra wood with the help of tool known as Draw
Knife. When finishing, the bat is sanded, the shoulder of bat is given its shape and the grip is
applied to the handle. Final finishing of cricket bats takes place with the help of horse’s shin
bone. Manufacturer logo are then added to the finished bat. Care must be taken when carving as
the knife is sharp.
Manufacturers grade the wood into various categories as soon as the blades are sawn to give an
approximate idea of stock levels (J.S.Wright & Sons Ltd, 2012). They are:
A Grade 1 Blade- best looking blade, though it will not necessarily play the best. There may be
some red wood evident on the edge of the blade. The grain on the face will be straight and there
will be a minimum of 6 grains visible. There may be the odd small knot or speck in the edge or
back but the playing area should be clean.
A Grade 2 Blade-has also very good quality and normally a larger amount of red wood can be
seen on the edge of a blade, this has no effect on the playing ability of the bat it is purely
cosmetic. Again there will be at least 6 straight grains on the face of the blade with maybe some
blemishes, pin knots or “speck” visible, we also put the top 2% of the excellent quality butterfly
blades that we get into Grade 2.
A Grade 3 Blade- The blade as it is supplied. This is a middle grade that is produced in much
higher numbers than the top grades. A Grade 3 Blade has up to half colour across the blade
which again has no direct relation to the playing ability of the wood, it just has less visual
attraction. There will be a minimum of 5 grains on the face of the blade which may not always be
perfectly straight. Again some small knots or butterfly stain may be present with sometimes
more prominent “speck”.
A Grade 4 Blade - normally over half colour or contains butterfly stain (see our page on
Imperfections in Willow). It will still play as well as the other grades. Any number of grains are
possible with often only 4 grains, the willow containing ‘butterfly’ stain is very strong, and there
could also be more “speck” and other faults.
TENNIS RACKET
A racket or racquet is a sports implement consisting of a
handled frame with an open hoop across which a network of
strings or catgut is stretched tightly. It is used for striking the
ball in tennis (Woodward, 2010).
Manufacturing
Most common rackets are now made of aluminum or of a
Figure 4: Tennis racket parts; Curtesy of
tenniscompanion.org
composite of graphite, fiberglass, and other materials. Aluminum
rackets are usually made of one of several alloys. One popular alloy
contains 2% silicon, as well as traces of magnesium, copper, and chromium. Another widely used alloy
contains 10% zinc, with magnesium, copper, and chromium. The zinc alloy is harder, though more brittle,
and the silicon alloy is easier to work (Lake, 2015).
The frame is formed by melting the aluminium and drawn through a die to get the shape. The rough
racket is then placed in a drilling machine, and holes are drilled for the yoke (the throat piece that holds
the bottom of the strings) on the sides for the strings, and at the base of the stick. The frames are then
placed in a sander to smooth out sharp edges left from the drilling (Woodward, 2010). After the rackets
are O tempered by heating then and quenching. This process hardens the aluminum, giving the racket
additional strength. The rackets are placed on a tray in an oven and heated to white-hot. Then the tray is
removed from the oven and the rackets are immersed in water. After tempering, the rackets may also be
anodized. They are immersed in a mild sulfuric acid solution, and an electric current is passed through the
bath. This treatment changes the surface of the aluminum, and gives the rackets a shiny finish
(Woodward, 2010). The rackets are then strung, usually with nylon or polyester and finished. The rackets
are tested for strength, durability, flex and other important criterias.
The material used must have the following criteria:

High strength to weight ratio is a key factor as the material must be strong enough to withstand
the impact of the oncoming ball and be light so that the user can swing easily.

Flexibility is also an important consideration. Flexible frames have greater shock absorption
properties to improve shooting precision, stiffer frames provide more power by keeping the head
rigid and truer to the incoming ball but the vibrations must be absorbed elsewhere, such as in the
arm (Claire Davis, 2010).

High stiffness, Young’s Modulus and durability- This ensures that the impact of the ball does not
easily deform the racket. The modulus must be within a range that allows flexibility but also
sturdiness. It must be able to undergo stress without wearing easily.
The Designation number for aluminum alloy used in rackets are as follows:
Silicon- 4XXX
Magnesium- 5XXX
Magnesium & Silicon-6XXX
Zinc-7XXX
The first digit (Xxxx) indicates the principal alloying element, which has been added to the aluminum
alloy and is often used to describe the aluminum alloy series. The second single digit (xXxx), if not 0,
indicates a modification of the specific alloy, if it is zero it indicates the original alloy and the last two
digits identify different aluminium alloys in the group or series (Aalco, 2005).
Example: 6061 and 6063 The 6 indicates that it is of Magnesium and Silicon alloy series, the 0 indicates
that there is no modification to the alloy, and the 61 and 63 identifies it in the 6xxx series.