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Chapter 1

Introduction

Overview

Materials engineering impacts on the quality of our lives. The go oning demand for high public presentation stuffs in structural applications has posed a great challenge for scientists and applied scientists. Materials engineering enables us to plan lasting constituents in military that serve several coevalss by understanding the features of stuff that we need in different operating conditions. The universe we live in has finite resources and because of that, stuffs applied scientists have responsibility of taking attention for the research, design, specification and stuffs building for future engineerings. As illustration, in military armoured vehicles, the stuff they use non merely strong plenty to protect against impact from missiles of conventional slug form, but besides light to cut down the weight of the vehicles.

Many of the merchandises presents are produced from massive stuffs. Majority of complexs have two constituents stuffs: a binder or matrix, and support. The support is typically stronger and stiffer than the matrix. The matrix holds the supports in an ordered design. Because the supports are on a regular basis discontinuous, the matrix every bit good helps to transform burden among the supports.

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Complexs are classify into three assorted classs, there are ; particle-reinforced, structural and fiber-reinforced. Sandwich panel is one illustration from structural complexs. It has two face sheets at the outer, coated by a nucleus which has lower in stiffness besides in strength interior. In add-on, the nucleus besides can be change with a honeycomb construction.

Honeycomb sandwich stuffs are one of such high public presentation stuffs. Sandwich, by definition, is made of three different beds, two thin face-sheets and a low denseness nucleus. It has a comparative high bending stiffness, lightweight, and high energy absorbing capacity, sandwich constructions have been used widely in aircraft constructions.

For this undertaking, the sandwich panel will be tested utilizing a ballistic impact trial for the ballistic opposition and angle consequence of incursion trial. Ballistic impact is concerned with the effects of missile on the mark. The ballistic impact is a really importance survey because it ensures the armour home base is made from a safe and optimal stuff for protection.

Problem Statement

Composite sandwich panels are of considerable involvement in aircraft constructions such as impact immune fuselage panels and as low weight panels in flying prima borders and flaps. They are susceptible to impact harm due to their thin complex teguments, but with suited nucleus stuffs may be designed to absorb impact energy.

Typical high speed impact trials on composite sandwich panels show that impact harm and failure, peculiarly with difficult missiles, is really localised consists of incursion of the outer composite tegument, harm to the nucleus and, if impact energy is high plenty, core incursion followed by interior skin harm or break.

Composite is used for energy absorbing application. Sandwich construction is used to heighten composite energy soaking up capableness. However, in order to imitate this local harm and failure detailed FE theoretical accounts are required to foretell and mensurate energy soaking up capableness. The theoretical account was validated with experimental trials by comparing numerical and experimental consequence.

With mention to Wan Awis ( 2010 ) researches have done, there are four chief jobs associating to armour panels.

The first is cost. Excessively complex armour readyings, largely those depending wholly on man-made fibres, can be responsible for a distinguished sum of the entire vehicle cost, and do its green goods non-profitable.

The 2nd is weight. Protective panel for heavy but movable armed equipment, for illustration Armoured Personnel Carrier ( APC ) and armored combat vehicles, is identified. Such armour by and large includes a solid bed of metal steel, which is planned to give protection adjacent to heavy and explosive missiles. Armor for light vehicles is predictable to avoid incursion of slugs of any sort, yet when hit at a impulse in the span of 700 to 1000 metres per second. On the other manus, due to weight restriction it is difficult to support light vehicles from high quality armor-piercing missiles, such as of 12.7 and 14.5 millimeter, because the weight of standard armour to digest such missile is such as to detain the mobility and operation of vehicles.

A 3rd is relates to ceramic home bases operate for single and light vehicle armour, which plates have be present discover to be susceptible to botch from mechanical impacts caused by stones, falls, etc.

A 4th is denseness. A solid armour panel, with air infinites between it ‘s a assortment of beds, enlarge the purpose profile of the vehicle. In instance of civilian retrofitted armoured vehicle which are equipped with internal armour, there is fundamentally no room for a solid panel in about all the countries necessitating armour.

Aims

To imitate the harm of composite sandwich constructions subjected to high-speed impact utilizing finite component.

To find the energy soaking up capableness of the constituents on the behaviour of the sandwich panel under impact burden utilizing MSC-Dytran.

To develop a of energy-absorption theoretical account of the impact composite construction.

To formalize a numerical theoretical account with existent experiment.

Scope of Research

To qualify a mechanical behaviour of C fibre panel by utilizing tensile, compaction testing and find the fibre volume force and denseness.

Design and formalize the numerical theoretical account.

Conduct a ballistic impact trial simulation.

Using the experiments informations to cipher the energy soaking up on the impact on the difference angle.

Chapter 2

LITERATURE REVIEW

2.1 Introduction to Composite

Sandwich composite stuff has been widely used in the aircraft and aerospace industries because of its high strength to weight and stiffness to burden ratios. Typically sandwich complex is formed by adhering thin, strong facesheets to a midst, lightweight nucleus. Each constituents of this complex is comparatively weak and flexible but when working together they provide and highly stiff, strong and lightweight construction. ( Thomson et al, 2005 )

A complex is a mixture of two stages called the matrix stage and are embedded in other stuffs, reenforcing stage, is in the signifier of fibres, sheets or atoms. The most usual constituents of sandwiches are a honeycomb nucleus and carbon-fibre teguments due to their high specific stiffness and strength. Sandwich constructions are really reasonable to such tonss. ( Aktay et al, 2005 )

Characteristically, the matrix is normally a ductile or strong stuff while reenforcing stuffs are strong with low densenesss. If the complex is fabricated and designed decently, it combines the stamina of the matrix with the strength of support to accomplish a combination of desirable belongingss. The disadvantage is that such complexs are on a regular basis more expensive than conventional stuffs. ( Schaffer et al, 1999 )

2.2 Fiber-Reinforced Composite

Fiber-reinforced composite stuffs have been used in such diverse application as ballistic capsule, cars, featuring goods, aircraft, off-shore constructions, civil substructure, electronics, and marine vehicles. ( Agarwal and Broutman, 1990 )

Fiber-reinforced complexs frequently aim to better the strength to weight and stiffness to burden ratios ( i.e. want light-weight constructions that are strong and stiff ) . Glass or metal fibres are by and large embedded in polymeric matrices. Fibers are available in 3 basic signifiers ( Shackelford, 1996 ) :

Continuous – Fibers are long, heterosexual and by and large layed-up analogues to each other.

Chopped – Fibers are short and by and large indiscriminately distributed ( fibreglass ) .

Woven – Fibers come in cloth signifier and supply multidirectional strength.

Figure 2.1 Conventional Illustration of Fiber Types: Unidirectional, Chopped & A ; Woven. ( Shackelford, 1996 )

Table 2.1 Properties of Selected Fiber-Reinforcing Materials. ( Shackelford, 1992 )

Group

Dispersed Phase

Tocopherol

[ Mpa ( ksi ) ]

Compressive Strength

[ Mpa ( ksi ) ]

Precent Elongation at Failure

C-glass

69×103 ( 10×103 )

4.5

E-glass

72.4×103 ( 10.5×103 )

4.8

S-glass

85.5×103 ( 12.4×103 )

5.6

Ceramic fibre

C ( black lead )

360-380 x103

( 49-55 x103 )

SiC

430×103 ( 62×103 )

Ceramic hair’s-breadth

Al203

430×103 ( 62×103 )

Polymer fibre

Kevlar

131×103 ( 19×103 )

2.8

Metal Filament

Boron

410×103 ( 60×103 )

Concrete sum

Crushed rock and sand

34-69 x103 ( 5-10 x103 )

69-340

( 10-50 )

Table 2.1 nowadayss a listing of normally used fibre stuffs ; normally utilised fibres include E-Glass ( low cost ) , Kevlar ( really low denseness ) and Carbon ( high strength and modulus ) . Beards are little, individual crystal fibres that have a about perfect crystalline construction. ( Shackelford, 1992 )

Table 2.2 Properties of Composite Reinforcing Fibers ( Gerstle, 1991 )

Material

( GPa )

( GPa )

( % )

( Mg/m3 )

( MJ/kg )

( MJ/kg )

E-glass

72.4

2.4

2.6

2.54

28.5

0.95

S-glass

85.5

4.5

2.0

2.49

34.3

1.8

Aramid

124

3.6

2.3

1.45

86

2.5

Boron

400

3.5

1.0

2.45

163

1.43

HS black lead

253

4.5

1.1

1.80

140

2.5

HM black lead

520

2.4

0.6

1.85

281

1.3

Tocopherol is Young ‘s Modulus, is interrupting emphasis, is interrupting strain and is denseness.

As seen in the Table 2.2, the fibres used in modern complexs have strengths and stifnesses far above those of traditional bulk stuff. The high strengths of glass fibres due to treating that avoids the internal or surface defects which usually weaken glass, and the strength and stiffness of the polymeric aramid fibre is a effects of the about perfect alliance of the molecular ironss with the fibre axis. ( Gerstle, 1991 )

hypertext transfer protocol: //info.lu.farmingdale.edu/depts/met/met205/fiberorient.JPG

Figure 2.2 Fiber Orientation in Fiber Reinforced Composites. ( Elgun, 1999 )

2.3 Carbon Fibers

Carbon fibres refer to fibres which are at least 92 % C in composing. They can be short or uninterrupted ; their construction can be crystalline, formless, or partially crystalline. ( Fitzer, 1990 )

Carbon_fibers_Kohlenstofffasermatte.jpg

Figure 2.3 Carbon Fiber ( Wikipedia )

Table 2.3 Properties of Assorted Fibers and Beards. ( Askeland, 1989 )

Material

Density ( g/cm3 )

Tensile Strength ( GPa )

Modulus of Elasticity ( GPa )

Ductility ( % )

Melting Temp ( A°C )

Specific Modulus ( 106 m )

Specific Strength ( 104 m )

E-glass

2.55

3.4

72.4

4.7

& lt ; 1725

2.90

14

S-glass

2.50

4.5

86.9

5.2

& lt ; 1725

3.56

18

SiO2

2.19

5.9

72.4

8.1

1728

3.38

27.4

Al2O3

3.95

2.1

380

0.55

2015

9.86

5.3

ZrO2

4.84

2.1

340

0.62

2677

7.26

4.3

Carbon ( high-strength )

1.50

5.7

280

2.0

3700

18.8

19

Carbon ( high-modulus )

1.50

1.9

530

0.36

2730

36.6

13

BN

1.90

1.4

90

1.6

2030

4.78

7.4

Boron

2.36

3.4

380

0.89

2450

16.4

12

B4C

2.36

2.3

480

0.48

2700

20.9

9.9

SiC

4.09

2.1

480

0.44

2980

12.0

5.1

TiB2

4.48

0.10

510

0.02

1277

11.6

0.3

Be

1/83

1.28

300

0.4

3410

19.7

7.1

Tungsten

19.4

4

410

0.98

147

2.2

2

Polyethylene

0.97

2.59

120

2.2

500

12.4

27.4

Kevlar

1.44

4.5

120

3.8

1982

8.81

25.7

Al2O3 beards

3.96

21

430

4.9

2550

11.0

53.3

BeO beards

2.85

13

340

3.8

2450

12.3

47.0

B4C beards

2.52

14

480

2.9

2700

19.5

56.1

SiC beards

3.18

21

480

4.4

15.4

66.5

Si3N4 beards

3.18

14

380

3.7

3700

12.1

44.5

Graphite beards

1.66

21

703

3.0

1890

43

128

Cr beards

7.2

8.90

240

3.7

1890

3.40

12

Table 2.3 compares the mechanical belongingss, runing temperature, and denseness of C fibres with other types of fibres. There are legion classs of C fibres. Postpone 2.3 merely shows the two high-performance classs which are labeled “ high strength ” and “ high modulus ” . Among the fibres ( non numbering the beards ) , high strength C fibres exhibit the highest strength while high modulus C exhibits the highest modulus of snap. Furthermore, the denseness of C fibres is rather low, doing the specific modulus ( modulus/density ratio ) of high-modulus C fibres exceptionally high. The polymer fibres, such polythene and Kevlar fibres, have densenesss even lower than C fibres, but their thaw temperatures are low. The ceramic fibres, such as glass, SiO2, Al2O3, and SiC fibres, have densenesss higher than C fibres. ( Askeland, 1989 )

2.3.1 Classification and Types of Carbon Fibers

Based on concluding heat intervention temperature, strength and modulus, C fibres can be classified into the undermentioned classs ( Hegde et al, 2004 ) :

Base on precursor fiber stuff:

Gas-phase-grown C fibres

PAN-based C fibres

Rayon-based C fibres

Mesophase pitch-based C fibres

Pitch-based C fibres

Isotropic pitch-based C fibres

Base on C fibres belongingss:

Super high-tensile ( SHT ) ( tensile strength & gt ; 4.5GPa )

Low modulus and high-tensile ( HT ) ( modulus & lt ; 100GPa, tensile strength & gt ; 3.0GPa )

Ultra-high-modulus ( UHM ) ( modulus & gt ; 450GPa )

High-modulus ( HM ) ( modulus between 350 – 450GPa )

Intermediate-modulus ( IM ) ( modulus between 200 – 350GPa )

Base on concluding heat intervention temperature:

Type-I, high-heat-treatment C fibres ( HTT ) , where concluding heat intervention temperature should be above 2000A°C and can be associated with high-modulus type fibre

Type-II, intermediate-heat-treatment C fibres ( IHT ) , where concluding heat intervention temperature should be around or above 1500A°C and can be associated with high-strength type fibre

Type-III, low-heat-treatment C fibres, where concluding heat intervention temperature non greater than 1000A°C. These are low modulus and low strength stuff.

Table 2.4 Characteristic and Applications of Carbon Fibers ( hypertext transfer protocol: //www.engr.utk.edu/mse/Textiles/CARBON % 20FIBERS.htm )

Physical strength, specific stamina, light weight

Aerospace, route and Marine conveyance, featuring goods

High dimensional stableness, low coefficient of thermic enlargement, and low scratch

Missiles, aircraft brakes, aerospace aerial and support construction, big telescopes, optical benches, wave guides for stable high-frequency ( GHz ) preciseness measuring frames

Good quiver damping, strength and stamina

Audio equipment, speaker unit for Hi-fi equipment, pickup weaponries, automaton weaponries

Electrical conduction

Automobile goons, fresh tooling, shells and bases for electronic equipments, EMI and RF shielding, coppices

Biological inertness and x-ray permeableness

Medical applications in prosthetic devices, surgery and x-ray equipment, implants, tendon/ligament fix

Fatigue opposition, self-lubrication, high damping

Textile machinery, genera technology

Chemical inertness, high corrosion opposition

Chemical industry, atomic field, valves, seals, and pump constituents in procedure workss

Electromagnetic belongingss

Large generator retaining rings, radiological equipment

2.4 Sandwich Panel

Sandwich panels can be merely defined as a three-layer construction that consists of two thin, outer teguments of high-strength stuff separated by a low-density and low-weight nucleus stuff. The nucleus stuff separates the face sheets that provide most of the strength to the construction. ( Hoffart et al, 2008 )

Sandwich panel nucleuss are low in denseness and lightweight ; but when combined with reenforcing fibres and rosin, they become improbably stiff, light and strong constructions. The nucleus helps absorb impact and distribute impact. In a honeycomb sandwich panel has much lower impact opposition as the tegument is non in full contact with the honeycomb nucleus although frequently stronger and stiffer. In a sandwich panel, the compaction strength of the nucleus helps forestall the sandwich from clasping, delaminating or pursing. ( Sandwichpanel.org, 2010 )

Sandwich panel usually consists of a low-density nucleus stuff sandwiched between two high modulus face teguments to bring forth a lightweight panel with exceeding stiffness as shown in Figure 2.4. The face skins act like the rims of an I-beam to supply opposition to the dividing face teguments and transporting the shear forces. The faces are typically bonded to the nucleus to accomplish the composite action and to reassign the forces between the constituents. ( Akour et Al, 2010 )

Figure 2.4 Illustration Sandwich Plate Geometry ( Akour et Al, 2010 )

hypertext transfer protocol: //upload.wikimedia.org/wikipedia/commons/thumb/b/b2/CompositeSandwich.png/220px-CompositeSandwich.png

Figure 2.5 Diagram of an Assembled Composite Sandwich ( A ) , and its Constituent Face Sheets or Skins ( B ) and Honeycomb Core ( C ) ( Alternately: Foam Core ) ( Wikipedia )

2.4.1 Face sheets

The face sheets provide the flexural rigidness of the sandwich panel. It should besides possess tensile and compressive strength. Since the carbon-epoxy complex has lower denseness than aluminium, important weight nest eggs can be realized by replacing them. The analysis of composite home bases by Harris et Al ( 1996 ) indicates that the sandwich plates with C epoxy face sheets have the lowest weight for different burden instances and that they are dimensionally more stable for a broad scope of temperatures.

2.4.2 Cores

The intent of the nucleus is to increase the flexural stiffness of the panel. The nucleus in general has low denseness in order to add every bit small as possible to the entire weight of the sandwich building. The nucleus must be stiff plenty in shear and perpendicular to the faces to guarantee that face sheets are distant apart. In add-on the nucleus must defy compressive tonss without failure. The nucleuss can be about any stuff, but in general autumn into the undermentioned four types. They are foam or solid nucleus, honeycomb nucleus, Web nucleus and Corrugated or truss nucleus. In Web nucleus and truss nucleus building, a part of the in-pane and bending tonss are besides carried by the nucleus elements. ( Sudharsan, 2003 )

2.5 Honeycomb Sandwich Panel

Table 2.5 Standard Compositions of Honeycomb Sandwich Panels ( Hexcel, 2001 )

Panel composing

Key features

Aluminium honeycomb nucleus, aluminum teguments.

Medium weight and stiffness at low cost.

Aluminium honeycomb nucleus, woven glass fiber teguments.

Lighter and less stiff than aluminium-skinned panels, at lower cost.

Non-metallic Nomex honeycomb nucleus, unidirectional or woven glass fiber teguments.

More resilient and higher cost than panels with aluminium honeycomb nucleus. Unidirectional fibers give greater stiffness, at higher cost than woven fibers.

Non-metallic Nomex honeycomb nucleus, unidirectional or woven C fiber teguments.

The lightest and stiffest panels, which is reflected in their cost.

Honeycomb is normally used as a nucleus in sandwiched constructions to run into design demands for extremely stressed structural constituents. When sandwiched between beds of C fibre, honeycomb shows extreme opposition to shear emphasiss. As a structural nucleus stuff, it is used in all types of aerospace vehicles and back uping equipment where sandwich construction offers aeromechanicss smooth surfaces, stiff panels of minimal weight, and high weariness opposition. The same structural belongingss are besides used for commercial applications for illustration snow and H2O skies, tools, floors and bulkheads. Honeycomb is besides used where designs need a agency of energy soaking up. It besides has a high stiffness and specific strength. Below are the characteristics of honeycomb ( Raymond et al, 2008 ) :

Compatible with most adhesives used in sandwich complexs

Good thermal stableness

Over expanded cell constellation suited for organizing simple curves

Excellent insulator belongingss

High strength to burden ratio

Corrosion resistant

High stamina

Thermally insulating

Excellent weirdo and weariness public presentation

Densities every bit low as 32 kg/m3 ( 2.0 lb/ft3 )

They are available in assortment of stuffs for sandwich constructions. They range from low strength and stiffness applications to high strength and lightweight applications such as aircraft industries. They can be formed to any form or curve without inordinate warming or mechanical force. Honeycombs have really high stiffness perpendicular to the faces and the highest shear stiffness and strength to burden ratios of the available nucleus stuffs. The most normally used honeycombs are made of aluminium or impregnated glass or aramid fiber mats such as Nomex and thermoplastic honeycombs. The chief drawback is high cost and trouble in managing. ( Sudharsan, 2003 )

2.5.1 Honeycomb Sandwich Panel Construction

A structural sandwich is a superimposed building formed by adhering two thin facings to a thick 1. The chief design construct is to infinite strong thin facings far plenty individually with a midst nucleus to guarantee the combination will be stiff, to give a nucleus that is strong and stiff plenty to keep the facings plane with an epoxy rosin ply, and to give a nucleus stuff of adequate shearing opposition. ( Bob Burdon, 2009 )

2.5.2 Aluminum Honeycomb

Aluminum honeycomb sandwich panels ( AHSP ) have been widely used in the Fieldss of aerospace, defence, railroad, Marine, automotive, athletics industry, and communicating for the virtues of light weight, high stiffness and high strength. But AHSP shows it ‘s vulnerable before impact force. McGowan et Al ( 1998 ) represented that fabrication defect would go on to AHSP caused by careless impact. This harm about did n’t tag on the face sheet externally but it would do strength decrease internally. It was besides stated that the conditions and grades of impact harm were variable harmonizing to the trial methods such as bead weight impact trial and air-gun trial etc.

Santosa et Al ( 1998 ) compared the impact strength between the honeycomb cell and froth. They found that the aluminium honeycomb could have better impact behaviour than aluminium froth under unidirectional burden and a combination burden of compressive and bending.

Reddy et Al ( 1998 ) analyzed the impact conformation with the experiential equation derived. Papka et Al ( 1997 ) evaluated the harm mechanism after impacting by optical analysis and supersonic c-scan. Kim et all ( 1995 ) found that trial frequence is lower than resonance frequence of honeycomb construction by utilizing mechanical electric resistance method in malice of assorted ways of happening the debonding honeycomb construction.

Kim et Al ( 2000 ) calculated the elastic modulus, shear modulus, Poisson ‘s ratio, compressive bending strength, shear bending strength and flexibleness of the kind of cell. In the research triangular and star cell was weak compressive bending strength and shear bending strength. But it had high flexibleness.

Features of aluminium honeycomb ( Plascore, 2009 ) :

High thermic conduction

Use temperatures up to 350 I¦ F

Fungi resistant

Excellent wet and corrosion opposition

Low weight/high strength

Fire resistant

2.6 Ballistic Impact

Harmonizing to Abrate ( 1998 ) , several definitions of ballistic impacts are used in the literature. Impacts ensuing in complete incursion of the laminate are frequently called ballistic impacts, whereas non-penetrating impact are called low-velocity impacts. Although non-penetrating impacts were studied extensively, impact incursion in composite stuffs has received well less attending. A different categorization consists of naming low-velocity impacts those for which emphasis moving ridge, a shear moving ridge, and Rayleigh moving ridges propagate outward from the impact point. Compressive and shear moving ridges reach the back face and reflect back. After many contemplations through the thickness of the laminate, the home base gesture is set up are called low-velocity impacts.

A simple method can be used to measure a passage speed beyond which stress moving ridge effects dominate. A cylindrical zone instantly under the impactor undergoes a unvarying strain across each cross subdivision as the moving ridge progresses from the forepart to the back face. With this simplifying premise, the job is reduced to that of the impact of a stiff mass on a cylindrical rod. Then, the initial compressive strain on the wedged surface is given by

where V is the impact speed and degree Celsius is the velocity of sound in the cross way. Typically, critical strains between 0.5 and 1.0 % are used to cipher the passage speed. For common epoxy matrix complexs, the passage to a stress wave-dominated impact occurs at impact speeds between 10 and 20m/s. Drop weight examiners by and large induce low-velocity impacts since a bead tallness of 5m will bring forth an impact speed of 9.9m/s and most examiners have a shorter bead tallness. ( Caldwell et al, 1990 )

In analyzing ballistic impacts, it is of import to mensurate the residuary speed of the missile accurately. This is a hard undertaking because many little atoms, fibres, and shear stoppers are pushed out by the missile during incursion. This stuff can trip the speed-sensing device being used and yield erroneous values. ( Arndt and Coltman, 1990 )

With high speed impact, it is really of import to mensurate the incident and residuary speeds of the missile in order to cipher the energy absorbed during the incursion procedure. Measuring the residuary speed of the missile utilizing optical detector is hard, since spalled stuff, shear stopper, and little atoms can travel in front of the missile as it exits the other side of the laminate, Zee et Al ( 1991 ) developed a microvelocity detector to mensurate the speed of a missile during the incursion procedure.

2.7 Energy Absorption

Cantwell and Morton ( 1985 ) calculated the ballistic perforation energy as the amount of the energy the mark absorbs by flection Ef, contact distortion Ec, delamination Ed and shear-out Es. For thicker marks, two distinguishable failure procedures are observed for the upper and lower parts of the specimen. ( Bless and Hartman, 1989, Bless et Al. 1990, Lin et al.1990, Cantwell and Morton 1990 ) .

A lower-bound estimation for the incursion energy for a thin laminate ( 4 to 16 plies ) was obtained by Cantwell and Morton ( 1989 ) . The hole produced by shearing of the fibres during perforation was shaped as a abbreviated cone get downing with the diameter of the missile and with a 45 I¦ half angle ( Figure 2.6 ) . The energy required to bring forth the hole was estimated by multiplying the break energy per unit country by the country of the frustum

where H is the laminate thickness and R is the projectile radius. For simple supported beams subjected to a cardinal force P, the strain energy is given by

where the P is cardinal force, L is length of the beam, E is Young ‘s Modulus and I is minute of inactiveness. ( Cantwell and Morton, 1989 )

Figure 2.6 Shear Failure Mode ( Abrate, 1998 )

Kinetic energy absorbed by the mark home base was determined by utilizing the contact ( Vs ) and residuary speeds ( Vr ) of the missile. Energy soaking up was calculated from the difference in kinetic energies of the missile before impact and after perforation as given by the undermentioned expression ( Wan Awis, 2009 ) :

2.8 Finite Element Analysis

Matthew ( 2003 ) explained in his book Finite Element Modeling of Composite Materials and Structures that the finite component ( FE ) analysis is simply an alternate attack to work outing the regulating equations of a structural job. hence, FE and classical methods will bring forth indistinguishable consequences for the same job, provided the former method is right applied.

Prevorsek et Al ( 1993 ) used a finite component theoretical account for imitating the distortion of a composite home base during ballistic impact, and a finite difference theoretical account for finding the temperature rise during the event. The analysis showed that a important temperature rise occurs at the projectile-composite interface, but because of the short continuance of the impact and the low thermic conduction of the composite, this temperature rise is confined of a really little part around the interface. The volume of stuff affected is excessively little to hold any consequence on public presentation.

Buitrago et Al ( 2009 ) was analyzed the perforation of composite sandwich constructions subjected to high-speed impact utilizing finite component theoretical account in ABAQUS/Explicit. The experimental trials provided information merely about the speed of the missile before the impact over the front tegument and after the perforation of the back tegument. However, the finite component theoretical account showed the development of the missile while it was traversing through the sandwich home base.

Talebi et Al ( 2009 ) investigated the effects of missile nose angle on fabric impact ; describe fabric distortion and failure under such type of lading. They obtained energy soaking up tendencies in conformity with missile nose angle and found the maximal projectile efficiency when perforating into fabric armour.

Chapter 3

Methodology

Introduction

Advanced complexs are a relatively new technology stuff. As a consequence, dependable database of stuff belongingss are rather rare. Generating belongings databases, hence, is frequently an of import portion of composite technology undertakings. To make justly in this research, the methodological analysis for this undertaking will steer this research from the beginning until the concluding consequence.

First of wholly, the acerb digestion method must be done to find the ply and weight of epoxy composite tegument. The acerb digestion method is conducted harmonizing to standard ASTM D3171. Then for the behaviour of composite sandwich construction, the tensile trial will be executing under the standard ISO 1924-2:1994 nut / ASTM D 3518. The flow of this research is clearly shown in Figure 3.1.

Figure 3.1 Mechanical and Modeling Testing Flow on Carbon Fiber and Sandwich Composites

Acid Digestion Method

Chemical digestion is described in ASTM D3171. A chemical must be selected that does non damage the fibres. Typical choices consist of sulphuric acid and H peroxide for peep and polyimide, azotic acid for epoxy and others as described in ASTM D3171. The fibre volume fraction is calculated as

where Vf = volume fraction of fibres, Wf = weight of fibres, Wm = weight of matrix, = denseness of fibres and = denseness of matrix

Nitric Acid Digestion Method Procedure

The C fibre specimens were so placed in single 100-ml glass beakers marked No. 1, 2, and 3.

These beakers were filled with 60 milliliters of 70 % azotic acid, covered with a ticker glass, and placed on a hot home base heated to about 120A°C ( 250A°F ) .

The specimens remained in the beakers on the hot home base for approximately 1 hr after the azotic acid began to boil, or until, based on a ocular review, no epoxy matrix stuff remained, adhering the single fibres together.

When this point had been reached, the beakers were removed from the hot home base and allowed to chill.

The azotic acid was carefully drained off so that all fibres remained in the beaker.

The azotic acid was poured into a waste container for disposal.

The beakers incorporating the C fibres were so refilled with 100 milliliter of distilled H2O.

The fibres were gently swirled in the beakers utilizing a glass stirring rod to clean the acid and epoxy matrix residue from the fibres.

Next, the distilled H2O was carefully drained off and fain of.

This procedure was repeated two more times, followed by a concluding rinse utilizing 95 % ethyl intoxicant.

The beakers were so placed in a drying oven at 49A°C ( 120A°F ) for a lower limit of 8 hours to thoroughly dry the fibres.

The beakers were so placed in a certain desiccator and allowed to chill to room temperature.

The beakers were so removed from the desiccator and the fibres in the single beakers were weighed utilizing the Mettler balance. This weight was recorded for each specimen.

The dry weight of each fibre and null volume specimen, the submersed weight of each specimen, the weight of the fibres entirely, and the densenesss of the fibre and matrix stuffs were used to cipher the fibre and null volume per centums of each specimen as described in ASTM D 3171-76 ( 1992 ) and ASTM D 792-66 ( 1992 ) .

Mechanical Testing

The mechanical testing of composite constructions to obtain parametric quantities such as strength and stiffness is a clip consuming and frequently hard procedure. It is, nevertheless, an indispensable procedure, and can be slightly simplified by the testing of simple constructions, such as composite sandwich construction. The informations obtained from these trials can be straight related with changing grades of simpleness and truth to any structural form. Some, such as the tensile trial, are widely recognized as criterions, whereas there are tonss of different trials for the measurings of shear belongingss.

Tensile Testing

Tensile proving is tallies harmonizing to ASTM criterion D 3518 / ISO 14129:2002 nut. Tensile proving utilizes the trial geometry as shown in figure 3.2 and consists of two parts: a cardinal part called the gage length, within which failure is expected to happen, and the two terminal parts which are clamped into a clasp mechanism connected to a trial machine.

Figure 3.2 Typical Tensile Composite Test Specimen ( Hodgkinson, 2000 )

These terminals are normally tabbed with a stuff such as aluminium, to protect the specimen from being crushed by the clasps. This trial specimen can be used for longitudinal, cross, cross-ply and angle-ply testing.

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Figure 3.3 Tensile Testing ( hypertext transfer protocol: //www.matweb.com/reference/tensilestrength.aspx )

Figure 3.4: Screw Action Grips With a 50 millimeter Gauge Length Clip-on Extensometer on Specimen. ( Hodgkinson, 2000 )

Finite Element Modeling

The orthotropic nature of each bed of sandwich laminate is represented in MSC Dytran so that stacking sequence and stuff belongingss of the composite sandwich construction can be decently incorporated into the analysis.

For the methodological analysis of finite component mold, foremost, the composite must be created by MSC Patran. The ply of the composite epoxy tegument must be determined. Second, the nucleus will be model by utilizing solid geometry. For the late advancement, the mold are shown in figure below.

Making a composite theoretical account.

Figure 3.5: Create Geometry

Figure 3.6: Create Mesh Seeds

Figure 3.7: Create Surface Mesh

Figure 3.8: Apply Boundary Conditions to The Model

Figure 3.9: Use Load to the Model

Figure 3.10: Check Element Conventions

Figure 3.11: Specify a Material Coordinate System

Figure 3.12: Use the Material Coordinate System to the Elementss

Figure 3.13: Analysis and Attach XBD Result File

The consequence for this mold can non obtain because during the analysis, the mistake is occurred.

Create Rigid incursion ball

Figure 3.14: Create Geometry ( Point )

Figure 3.15: Create Geometry ( Surface )

Figure 3.16: Create Mesh

Figure 3.17: Mirror/Transform Mesh

Figure 3.18: Equality All Nodes

Figure 3.19: Define Ball Material Properties

Figure 3.20:

Figure 3.21:

Figure 3.22:

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