Perforation of Composite Sandwich Panels

Perforation of Composite Sandwich Panels CHAPTER 1 INTRODUCTION 1.1 Introduction The use of sandwich structures has been increasing in recent years because of their lightweight and high stiffness. Commonly, the naval industry and transportation uses the E-glass fibers while the aerospace industry uses composite structures such as carbon fiber. The use of sandwich panels with composite facesheet in the naval industry is particularly appealing because they have better corrosion and environmental resistance and reduced magnetic signatures when compared to double-hull construction steel ships. On the other hand, composite sandwich panels are easily susceptible to damage by a strange object impact. The damage may be visible, penetration or perforation, or invisible, internal delamination and debonding. Both types of damages will result in stiffness and strength reduction. It is then important to study the impact behavior of composite sandwich panels. Failure in composite structures can be caused by low, high and extremely high or localized impact. An impact caused by a foreign body initiates two waves from impact point in a panel: a through-thickness wave and a transverse shear wave. Whether or not these waves play an important role in the impact response of the panel depends on the actual contact duration between the projectile and panel and the time it takes the transverse shear wave to reach the panel boundary. Figures 1.1 (a)-(c) show three-impact scenarios: low-velocity, high-velocity and ballistic impact. In low-velocity impact, the contact force duration is long compared to the time it takes the transverse shear wave travel to reach the plate boundary. Many waves reflect back and forth across the side dimension of the panel. In high-velocity impact, the contact force duration is much shorter than the transverse shear wave travel time through the panel. Usually high-velocity impact is the same with perforation and localized damage of the panel. Ballistic impact deals only with through-thickness wave propagation. During ballistic impact, there is complete perforation of the panel with little or no panel deformation. The contact force duration is approximately the wave travel time through the panel thickness. Ballistic impact usually involves the study of penetration mechanics. Low-velocity High-velocity Ballistic Impact The projectile to panel mass ratio will control whether wave propagation effect dominates the panel impact response and then suggested that a mass ratio be use as a parameter to determine impact response. It was shown that small mass impacts produce more damage than high-mass impacts having same kinetic energy. While small-mass impacts were defined by wave-controlled response, large mass impacts were defined by boundary-controlled response. Common examples of low-velocity impact are of bird strikes, collision with floating object, and dropped tools, may cause damage. Underwater blast or debris from a faraway explosion and air was considered as a high-velocity impact situation. Examples of ballistic impact would be a bullet or fragments from a nearby explosion hitting the panel. Another important factor governing the impact on composite structures is the ballistic limit. The ballistic limit is defined as the highest velocity of the projectile to cause perforation. When the residual velocity (exit) of the projectile is zero, then the initial velocity of the projectile that causes perforation is the ballistic limit of the sandwich panel. The ballistic limit may be calculate analytically or determined experimentally. In the experimental method, sandwich panels are shoot with projectiles over narrow range of velocities to either just cause penetration or to just perforate the panel. There exists a striking velocity at which 50% of the panels are completely perforate above this value and remaining 50% are partly penetrate below this value. This striking velocity is expresse as V50, which is the ballistic limit of the panel. In the analytical approach, the ballistic limit is determined by the conservation of energy principle. The approach is complex because it inc ludes a variety of factors like core thickness, facesheet thickness, shape of the projectile, core crushing stress, and so on. 1.2 Problem Statement This topic was an expansion of the Wan Awis research. He has done only an experimental work. For impact application, we need to predict skin and core material thickness. Since impact phenomena depend on numerous parameters such as material properties or projectile geometry, a numerical model, validated experimentally, is necessary to allow the study of the influence of several parameters without making costly experimental tests. This will definitely enhance the development of our military technology and achievements in the future because of the ability of this software to cut production cost and time consuming of the experimental work. The numerical figures have been compared to modal test results aiming mainly to validate the studies. Simulation based on finite element analysis (FEA) must not exceed  ± 15% error or this simulation could be claimed not acceptable. 1.3 Objective To simulate the damage of composite sandwich structures subjected to high-velocity impact using finite element analysis. To determine the energy absorption capability of the components on the behavior of the sandwich panel under impact load using ANSYS AUTODYN 13.0 To validate a numerical model with actual experiment. 1.4 Scope of Works To characterize a mechanical behavior of carbon fiber panel by using tensile and determine the fiber volume force and density. Design and validate the numerical model. Conduct a ballistic impact test simulation. Using the experiments data to calculate the energy absorption on the impact. CHAPTER 2 LITERATURE REVIEW 2.1 Introduction A great deal of research has been conducted in the area of impact of composite structures. In this chapter, previous work done on the impact response of laminated composite plates and composite sandwich panels will be reviewed. 2.2 Impact of Composite Laminates A detail study of impact of composite laminates in the three impact regimes ballistic impact, low-velocity and high-velocity is presented in this section. 2.2.1 Low-velocity Impact Abrate, 1998 give a specific review on different analytical models of impact on composite laminates. He classified impact models into four groups: impact on infinite plate model, energy balance models, spring-mass models, and complete models. In the energy balance model, the initial kinetic energy of the projectile is used to calculate the deformation of the composite laminate. The velocity of the projectile reaches zero at the maximum deflection of the composite laminate. At this point, all of the kinetic energy of the projectile is converted to strain energy needed to deform the composite laminate. Energy balance model assumes that the structure behaves in quasi-static manner. The time history of force and deflection are obtained using the spring-mass model representing the composite laminate. The model shown in Figure 2.1 consists of nonlinear contact stiffness (K), one spring representing the linear stiffness of the structure (Kbs), another spring for the nonlinear membrane stiff ness (Km), effective mass of the structure (M2) as well as the mass of the projectile (M1). Equations of motion are written from a free body diagram. The infinite plate model is used when the deformation wavefront has not reached the boundary but if the wave reaches the plate boundary then this model is not an appropriate one to use. In the complete model, the dynamics of the structure and projectile are taken into explanation. Appropriate plate theory has to be selected and used. In many cases the classical plate theory can be used but when transverse shear deformations become significant, higher-order theories must be used. One of the earliest studies on the impact of composite laminates was by Goldsmith et al, 1995, who conducted high-velocity and quasi-static impact tests on carbon-fiber laminates by using a cylindro-conical projectile. Three different specimen of varying thickness were considered. Energy balance principle was used to predict the dynamic penetration energy, static penetration energy, and also the ballistic limit of the composite laminate. The fiber failure accounted for most of the energy absorbed. The predicted theoretical energy was in good agreement with measured energy for thin laminates but not for the thick laminates. This was approved to the fact that transverse shear deformation played an important responsibility in thick laminates subjected to low-velocity impact. The effect of transverse shear deformation was not dominant due to its quick occurrence in the high-velocity impact of laminates. Therefore, the predicted energy in the dynamic case was always close to but less than the measured energy for the thin and thick laminates. The predicted ballistic limit was less than measured values due to the nonlinear factors. Cantwell, 2007 studied the influence of target geometry in the low-velocity impact of composite laminate. The tests were performed on GFRP plates with hemispherical indenter on either circular or square supports. He used energy-balance model to predict the plate deflection and the delamination area of the laminated structure. His study stated that there is little or no influence of target geometry on the failure modes. It also suggested that delamination was dependent on interlaminar shear stress and increasing the plate diameter required more energy for damage initiation. Hou et al., 2000 predicted impact damage in composite laminates using LSDYNA 3D. The numerical results were compared to experimental results on low-velocity impact on composite laminate with an initial velocity of 7.08 m/s The Chang-Chang failure criteria was modified taking the shear stress into consideration and the model was implemented in DYNA 3D. 2.2.2 High-velocity Impact In 1988, Cantwell performed high-velocity impact tests of CFRP laminates with 6 mm diameter, 1g steel ball as the projectile. The influence of fiber stacking sequence and target geometry was study. The experiments reveal that varying the target geometry had no significance on initial damage caused. While the damage initiated in the distal facesheet in thin laminates, however, in thick laminates it initiated from incident facesheet. Zhao et al., 2007 investigated the failure modes in composite laminates subjected to high-velocity impact. Three different laminates were subject to impact by hemispherical projectile in the range of 10-300 m/s. An energy balance was considered and equations for residual velocity for the laminates were given in terms of the mass of the projectile and striking velocity. The thickness and stacking sequence were finding to play an important role in the energy absorption. Cheng et al., 2007 developed an analytical model based on the spring-mass model for high-velocity impact of a blunt ended and a sharp-ended projectile on thick composite laminates. They considered the effect of moving boundary due to the propagation of shear wave. The analysis was modeled using series of quasi-static events. At the end of each quasi-static step, the failed layers were remove based on punch shear damage and fiber damage criteria, and the wave front was moved outwards. While the first spring stiffness constant was measure based on the penetration depth of the projectile, the second spring stiffness constant was measured based on the bottom node of the plate. 2.2.3 Ballistic Impact Silva et al., 2005 performed numerical simulations of ballistic impact on thin Kevlar 29 composite laminates using a fragment-simulating projectile. The laminate material model was simulating using AUTODYN and the projectile was modeled using Johnson-Cook strength model. Finite element mesh for both laminate and projectile was generating using True Grid. Accurate predictions of ballistic limit (V50) and the failure modes were made. Ballistic limit is the minimum velocity of impact at which a given projectile just perforates a given target. On occasion, the term is also used to identify the maximum impact velocity at which the projectile can penetrate into the target with perforation. It is often defined statistically as the impact velocity for which the projectile has a 50% probability of perforating the target; it is then denoted by V50. Guild et al., 2007 conducted numerical simulations of ballistic impact on composite laminates and compared them with experimental results. The laminates were made of E-glass/vinyl ester resin with varying thickness and ball bearings of varying mass were use as projectiles. The damage modes included fiber failure, matrix failure, penetration, and delamination. Hashin failure criteria was use to determine the damage mode. Delamination was modeled using an interface between the two plies. As the force increased between two nodes above the specified value, the nodes were untied and the delamination increased. The ballistic limit from experiments was in good agreement with numerical results Naik et al., 2008 studied the ballistic impact behavior of thick composites. E-glass/epoxy laminates of varying thickness were subject to high-velocity impact. The effects of projectile diameter, projectile mass and laminate thickness on the ballistic limit were studied. Wave theory and an energy balance were use to predict the ballistic limit of the laminate. The contact duration of the projectile with the laminate was maximum when the initial velocity was equal to ballistic limit and decreased when the initial velocity increased beyond the ballistic limit. Deka et al., 2008 conducted ballisitic impact on E-glass/polypropylene composite laminates with cylinder-shaped projectiles. The experimental results were validating with numerical analysis using LS-DYNA. Although the laminate was modeling in Hypermesh, LS-DYNA was used to analyze failure mechanisms. The analytical model was base on energy conservation and failure in the numerical analysis was predicted based on Hashins failure criteria. 2.3 Impact of Composite Sandwich Panels In this section, a detail study of impact of composite sandwich panels in the three impact regimes low-velocity, high-velocity and ballistic impact is presented. 2.3.1 Low-velocity Impact Mines et al., 1998 investigated quasi-static loading and low-velocity impact behavior on two different composite sandwich panels. While the first panel was made up of E-glass/vinyl ester skin and Coremat ® core, the second panel was made of Eglass/epoxy skin and aluminium honeycomb core. The first panel with Coremat ® core had failed in the sequence of core shear, debonding, and distal facesheet damage and incident facesheet failure. The second panel failed by core shear, debonding, incident facesheet failure and then distal facesheet failure later. In the low-velocity impact tests, the failure pattern remained the same in both the panels as of the quasi-static tests. The core properties and impact velocity govern the energy absorption capability of the sandwich panel. Wen et al., 1998 investigated the penetration and perforation of composite laminates and sandwich panels under quasi-static, drop-weight and ballistic impact tests by flat-faced, hemispherical-ended and conical-nosed indenters/projectiles. They categorized the impact on laminates and sandwich panels into low-velocity impact and wave-dominated (high-velocity/ballistic impact) response. It was also stated in the research that sandwich panels subjected to low-velocity impact have similar load-displacement characteristics as of quasi-static loading case. The perforation energy required by flat faced projectile was more than hemispherical-ended and conical shaped projectiles in high-velocity impact. Schubel et al., 2005 investigated quasi-static and low-velocity impact behavior of sandwich panels with woven carbon/epoxy facesheets and PVC foam. The low-velocity impact model behaved similar to quasi-static loading case when loads and strain levels were same. The static indentation response was compared to the numerical results obtained using ABAQUS and were in good agreement. A membrane solution, assuming membrane in the core affected region and plate on elastic foundation in the rest of sandwich panel was in poor agreement with the numerical results. Hoo Fatt et al., 2001, developed static and dynamic models of sandwich panels subjected to low-velocity impact. They investigated the behavior of sandwich panels having carbon/epoxy skins and a Nomex honeycomb core with a hemispherical indenter under various support conditions such as simply supported, fully clamped, and rigidly supported. Spring-mass models were considered to determine the load-displacement curve. They also investigated the damage initiation of sandwich panels under low-velocity impact loading. The initial mode of damage depended upon the panel support conditions, projectile nose shape, geometry of the specimens, and material properties of the facesheet and core. Various failure patterns were studied and solutions based on them were derived separately. The analytical solution for the ballistic limit was also found and results for thick laminates were in better agreement than thin laminates. Suvorov et al., 2005 performed numerical analysis on sandwich panels with foam core and studied the effect of interlayer in between the top facesheet and foam core. The foam core was modeled as crushable foam in ABAQUS. While the polyurethane (PUR) interlayer reduced the deformations in both the core and the composite facesheets, the elastomeric foam (EF) interlayer offered a better protection for the foam core alone. Besant et al., 2001 performed numerical analysis on sandwich panels with aluminium honeycomb core. The metal honeycomb core was modeled as elastic perfectly plastic material. A quadratic yield criterion was proposed for the core material, which included both normal and transverse shear stresses. The importance of core plasticity in finite element analysis was explained. 2.3.2 High-velocity Impact A great deal of work has been done in the area of low-velocity impact of laminates and sandwich panels and high-velocity impact of laminates but limited work has been presented in the domain of high-velocity and ballistic impact of sandwich panels. The following describes some recent studies on the high-velocity impact of composite sandwich panels Velmurugan et al., 2006 studied the projectile impact on composite sandwich panels in the range of 30-100 m/s. The sandwich models in this study were not the typical sandwich panels in the conventional sense. They had a core height comparable to the facesheet thickness and acted as a bonding agent between the facesheets. Energy-balance model was used to determine the ballistic limit of three different sandwich panels. They assumed the sandwich panel as a single plate since the foam layer was thin and comparable to facesheet thickness. Also uniform failure mechanism along the through thickness direction was assumed in their model. Skvortsov et al., 2003 developed an analytical model using energy-balance principle to determine the ballistic limit of composite sandwich panels subjected to high velocity impact. Two different sandwich panels were subjected to high velocity impact using three different projectiles. These tests were conducted on simply supported and rigidly supported boundary conditions, and the initial velocity was varied in the range of 70-95 m/s. The predicted panel energy was close to the experimental values and the error was due to the strain-rate effects, plastic behavior, and hardening phenomena, which are not consider in the analysis. 2.3.3 Ballistic Impact Kepler et al., 2007 conducted ballistic impact on sandwich panels consisting of GFRP plates and Divinycell H80 core, with three different projectiles. Lumped spring mass model was use to calculate force histories and panel response. Concentric rings connected by shear springs represented the sandwich panel. In this model, core shear deformation was assumed as the single significant contributor to the sandwich panel stiffness. The facesheet orthotropic was neglected in the panel response. Four different force histories: constant force, triangular force, sine series, and combination of sine and triangular force were used to calculate the energy loss in the panel. Of these, triangular and combined force gave results in better agreement with experimental results. 2.4 Aluminium Honeycomb For design and construction of lightweight transportation systems such as satellites, aircraft, high-speed trains and fast ferries, structural weight saving is one of the major considerations. To meet this requirement, sandwich construction is frequently use instead of increasing material thickness. This type of construction consists of thin two facing layers separated by a core material. Potential materials for sandwich facings are aluminium alloys, high tensile steels, titanium, and composites depending on the specific mission requirement. Several types of core shapes and core material are been applied to the construction of sandwich structures. Among them, the honeycomb core that consists of very thin foils in the form of hexagonal cells perpendicular to the facings is the most popular. A sandwich construction provides excellent structural efficiency, i.e., with high ratio of strength to weight. Other advantages offered by sandwich construction are elimination of welding, superior insulating qualities and design versatility. Even if the concept of sandwich construction is not very new, it has primarily been adopt for non-strength part of structures in the last decade. This is because there are a variety of problem areas to be overcome when the sandwich construction is applied to design of dynamically loaded structures. Other investigators have previously carried out noteworthy theoretical and experimental studies on linear elastic and nonlinear behavior of aluminium sandwich panels. Kelsey et al., 1985 derived simple theoretical expressions of the shear modulus of honeycomb sandwich cores. Witherell, 1977 performed an extensive theoretical study for structural design of an air cushion vehicle hull structure using aluminium honeycomb sandwich panels. Okuto et al., 1991 showed the validity of the so-called equivalent plate thickness method in which a honeycomb sandwich panel subjected to inplane loads is approximately replaced by a single skin panel with equivalent plate thickness. Kobayashi et al., 1994, studied Elasto plastic bending behavior of sandwich panels. An experimental study was undertaken by Yeh et al., 1991 to investigate the buckling strength characteristics of aluminium honeycomb sandwich panels in axial compression. Kunimo et al., 1989 both, have studied the characteristics of the energy absorption capacity of bare honeycomb cores under lateral crushing loads theoretically and experimentally. 2.5 Ballistic Limit The ballistic limit may also be defined as the maximum velocity at which a particular projectile is expected to consistently fail to penetrate armor of given thickness and physical properties at a specified angle of obliquity. Because of the expense of firing tests and the impossibility of controlling striking velocity precisely, plus the existence of a zone of mixed results in which a projectile may completely penetrate or only partially penetrate under apparently identical conditions, statistical approaches are necessary, based upon limited firings. Certain approaches lead to approximation of the V50 Point, that is, the velocity at which complete penetration and incomplete penetration are equally likely to occur. Other methods attempt to approximate the V0 Point, that is, the maximum velocity at which no complete penetration will occur 2.6 Energy Absorption Mechanism of Composite Materials The research was done by Naik and Shrirao at 2004. Impact loads can be categorized into three categories which is low-velocity impact, high-velocity impact and hyper-velocity impact. This classification is made because of change in projectiles velocity will result in different mechanisms in terms of energy transfer between projectile and target, energy dissipation and damage propagation mechanism. Basically, ballistic impact is considered as low-mass high velocity impact. In this impact event, a low-mass projectile is launched by source into target at high velocity. It is unlike low-velocity impact that involved high-mass impactor impacting a target at low velocity. In view of the fact that ballistic impact is high velocity event, the effect is localized and near to impact location. According to Naik et al. (2006), seven possible energy absorbing mechanisms occur at the target during ballistic impact. Those mechanisms are cone formation at the back face of the target, deformation of secondary yarns, tension in primary yarns/fibres, delamination, matrix cracking, shear plugging and friction between the projectile and the target. Then, the researchers formulated all these energies into equation whereby the total energy absorbed by the target is summation of kinetic energy of moving cone EKE, shear plugging ESP, deformation of secondary yarns ED, tensile failure of primary yarns ETF, delamination EDL, matrix cracking EMC and friction energy EF. ETOTALi = EKEi + ESPi + EDi + ETFi + EDLi + EMCi + EFi Mines et al. (1999) identified three modes of energy absorption when analysed the ballistic perforation of composites with different shape of projectile. These energy absorptions are local perforation, delamination and friction between the missile and the target. However, the contribution of friction between the missile and the target in energy absorption is low compared to the other two. In terms of local perforation, three through-thickness regimes can be identified, namely: I shear failure, II tensile failure and III tensile failure and delamination. Out of these three regimes, the through-thickness perforation failure is dominated by shear failure. Similar observation has been made by other researcher for thick graphite epoxy laminates whereby the perforation failure is dominated by shear failure. The third main energy absorption mechanism is delamination. Delamination can propagate under Mode I (tensile) and Mode II (shear) loading and each mode can dominate each other depend ing on structural configuration of the composite as well as material properties. Therefore, it can be predicted that the total perforation energy is a summation of energy absorption due to local perforation, delamination and friction between the missile and the target. Epred = Ef + Esh + Edl where Ef = friction between the missile and the target; Esh = local perforation; Edl = delamination Apart from that, Morye et al. (2000) has studied energy absorption mechanism in thermoplastic fibre reinforced composites through experimental and analytical prediction. They considered three mechanisms that involved in absorbing energy by composite materials upon ballistic impact. The three energy absorption mechanisms are tensile failure of primary yarns, elastic deformation of secondary yarns and the third mechanism is kinetic energy of cone formed at back face of composite materials. They concluded that kinetic energy of the moving cone had a dominant effect as energy absorption mechanism for composite materials. However, they neglected a delamination as one of the factor contributed to the failure of composite materials during ballistic impact. 2.7 Kinetic Energy Equation Kinetic energy (KE) attack is a penetration of the residual energy of a projectile. A projectile can give a certain amount of energy to attack and damage a vehicle if the projectile sufficient residual energy when it arrive at the target. This residual is very important to overmatch the capability and strength of the target material to resist penetration, and then it will penetrate. Kinetic energy shot can be presented with the simple law of physic. K.E =  ½ Mprojectile Vprojectile2 Increasing the mass (Mprojectile) of the shot increases its energy, but the real payoff comes from increasing its velocity (Vprojectile). If the diameter of the shot fills the whole gun barrel, the projectile becomes heavier and difficult to accelerate to required velocity with the length of the barrel. Additionally, a large diameter solid shot will provide more energy to penetrate the armour plate compared to a projectile which has the same mass but a smaller diameter. Consequently, the larger shot is not only less effective at the target but it is difficult to give it the necessary velocity. According to Chang et al., 1990, depth of penetration at the target will depend not only on residual energy, but also on shape and size of the projectile. The curve shape at the projectile head is more important, as it must not only able to pierce the armour but the shoulders of the shot must also support the remainder so that it does not break up on its way through the armour. If for given mass the diameter of the shot is reduced and is length increased, then for the same residual energy the shot will penetrate further, as it is working on a smaller cross section area of armour. The ratio of length-to-diameter is called slenderness ratio. Any projectile with ratio in excess of 7:1 cannot be spin stabilized it is not until they reach a ratio approximately 20:1 that they can call long rod. So, based on those discussions above, we can conclude that energy absorption can be performed by this relation Eabsor = Ein Eout = [ ½ Mprojectile Vin2] [ ½ Mprojectile Vout2] =  ½ Mprojectile (Vin2 Vout2) So, Eabsorbed =  ½ Mprojectile (Vin2 Vout2) 2.8 Tsai-Hill Failure Criterion Hill, 1950 proposed a yield criterion for orthotropic materials: G+HÏÆ'12+F+HÏÆ'22+F+GÏÆ'32-2HÏÆ'1ÏÆ'2-2GÏÆ'1ÏÆ'3-2FÏÆ'2ÏÆ'3+2LÏ„232+2MÏ„132+2NÏ„122=1 This orthotropic yield criterion will be used as an orthotropic strength or failure criterion in the spirit of both criteria being limits of linear elastic behavior. Thus, Hills yield stresses F, G, H, L, M and N will be regarded as failure strengths. Hills criterion is an extension of von Mises yield criterion. The von Mises criterion, in turn, can be related to the amount of energy that is used to distort the isotropic body rather than to change its volume. However, distortion cannot be separated from dilatation in orthotropic materials, so Equation 2.8 is not related to distortional energy. Unfortunately, some authors still mistakenly call the criterion of Tsai-Hill a distortional energy failure criterion. The failure strength parameters F, G, H, L, M and N were related to the usual failure strength X, Y, and S for a lamina by Tsai. If only Ï„12 acts on the body, then, because its maximum value is S, 2N=1S2 Similarly, if only ÏÆ'1 acts on the body, then G+H=1X2 And if only ÏÆ'2 acts, then F+H=1Y2 If the strength in the 3-direction is denoted by Z and only ÏÆ'3 acts, then F+G=1Z2 Then, upon combination of Equations (2.10), (2.11) and (2.12), the following relations between F, G, H and X, Y, Z result: 2F=1Y2+1Z2-1X2 2G=1X2+1Z2-1Y2 2H=1X2+1Y2-1Z2 For plane stress in the 1-2 plane of a unidirectional lamina with fibers in the 1-direction, ÏÆ'3 = Ï„13 = Ï„23 = 0. However, from the cross sectional of such a lamina in Figure 2.3, Y = Z from the obvious geometrical symmetry of the material construction. Thus, Equation (2.8) leads to ÏÆ'12X2-ÏÆ'1ÏÆ'2X2+ÏÆ'22Y2+Ï„122S2=1 as the governing

Critical Lens Essay :: essays papers

Critical Lens Essay Whenever someone performs a task, he/she can labor over it carefully, or do a rushed job. A student writing an essay describing the causes of the American Revolution, or a president proposing ways to end World War II illustrate two situations where both simple and complicated ways to address a problem exist. Writing a non-analytical response to the essay question would be easy to do. Likewise, dropping atomic bombs over cities, razing them and eliminating many people would not be entirely morally correct. H.L. Mencken^s assertion that ^for every problem there is one solution which is simple, neat, and wrong^ is excellent for assessing the literary elements in two works: Fences by August Wilson and Snow Falling on Cedars by David Guterson. Fences is filled with difficulties between characters, and many of these were not reconciled in a proper manner. One problem involved Cory, a high school student and his father, Troy. Cory, an accomplished football player wanted to focus on his team and play in college. However, his father was against Cory^s goals, insisting he prioritize his work and house chores over the football. Ordinarily, there is nothing wrong with a parent making major decisions for his/her children, but in this case, Troy^s solution to the problem was simply to go behind Cory^s back and revoke his membership on the team. Going behind one^s back is an easy way out of resolving a problem^the person was plainly too indolent to spend the time to find a more mutually acceptable solution. Troy^s demeanor is unacceptable not only with Cory, but also with other characters in the book. For example, when Lyons asks him for a small amount of money, Troy creates a big scene, detailing problems he had had in the past with getting credit, such as paying for furniture through ten-dollar monthly installments. It is clear that Troy is rather selfish, for he tries to keep what little amount of money he has for himself. In Snow Falling on Cedars, readers observe different types of problems. While those in Fences tend to be between two people, those in Guterson^s book usually involve a large group of people, often the entire town of San Piedro. The principal question throughout the novel centers around who killed Carl Heine. The entire town seems to show prejudice against Kabuo, primarily because he is Japanese. This prejudice is obvious even in affairs unrelated to Kabuo^s trial. In a descriptive paragraph about life in San Piedro, readers learn that Japanese workers at the Port Jefferson mill were

The Uk Diabetes Problem Health And Social Care Essay

I have done the nursing occupation in my back place state Nepal and now I am making the attention helper for aged people in attention place. Most of the occupants are enduring from different diseases, such as diabetes, dementedness.In my unit most of occupant are suffered from diabetes. In my state Nepal I have seen many patients of diabetes, from where I got the more cognition about the diabetes. Not merely UK people but besides whole universe people is enduring from the diabetes. Many research are conducted on this instance, diabetes affects six per centum of the universe ‘s population and its prevalence is duplicating every coevals.There are presently over two and half million people diabetes in UK and there are more than half a million people with diabetes who have the status and do n't cognize it. Harmonizing to diabetes UK statistics show that over 80 % of people diagnosed with type2 diabetes and corpulence. Diabetes patient spend an norm of & A ; lb ; 4500 yearly on costs for handling their diseases in the universe. The cost of diabetes to the national wellness service stands at about & amp ; lb ; 1 million per hr and is increasing quickly a new study indicates ( www.diabetes.co.uk ) .Diabetes 29/04/2011 ) histories for about a ten percent of NHS budget each twelvemonth a entire exceeding & A ; lb ; 9 billion. The complications of diabetes are legion and deathly and include amputation, bosom disease kidney failure and sightlessness, the study highlights the facts that eight out of 10 people with diabetes dices of bosom disease and stroke.Goverment is passing tonss of money and has committed to guaranting there is greater focal point on speed uping the gait of betterment in diabetes attention. Increasing the diabetes patients evidently affect the system and economic system position of the state because alternatively of utilizing money in productive work, concern and building authorities is paying for diabetes which is straight influences the state. HEALTH Wellbeing AND QUALITY OF LIFE It is really complicated and difficult to specify wellness, there are 100s of positions from different writer and different organisations.As we know all of the accept the definition of universe wellness organisation, wellness is a complete, physical mental and societal well- being and non simply the absence of disease and frailty which means wellness is in relationship with different factors like single, physical, societal physiological, emotional, environmental and cultural it means wellness is non merely absence of disease. Person may go ailment with his mental and societal position and his milieus. Health is really of import factor in human life as we know the stating wellness is wealth. Same like wellness wellbeing is besides the of import factor of healthy and affluent life. Actually well-being is being healthy felicity, free from emphasis, mentally, physically, socially and emotionally. Health and wellbeing are the most of import constituents of healthy life. These are the constituent which determines the quality of life. Along with wellness and well-being quality of life is really of import which play large function in life of single. Quality of life denotes how the person is? His day-to-day life activities, his or her wellbeing. This is the term which determines populating status, installations, possibilities, security, satisfaction, income, employment, nutrient, instruction, quality wellness services, hygiene, public assistance and support. It is different from everyone. The chief thing determine quality of life is our ability to bask all that life has to offer for cases, the ability to walk, talk and experience all contributes to our all quality of life. ( journal.diabetes.org volume 30/04/2011 ) Diabetess During our life clip we know is likely to diabetes mellitus, better known as diabetes.Diabetes is found when the sugar in our blood is excessively high. It happens when something goes incorrect with the manner our organic structure uses the nutrient we eat. Our organic structure breaks down nutrient into sugar, fat, and protein. Our organic structure uses sugar for energy. A endocrine called insulin helps our organic structure turn sugar into energy. Insulin is made in the pancreas, which is located near our tummy. When we eat, our pancreas supposed to do the right sum of insulin to travel the sugar from our blood into our organic structure ‘s cells. When we have diabetes, we have no insulin or non adequate insulin, or our organic structure does non react to the insulin it makes. The sugar stays in our blood. When excessively much sugar builds up in our blood and reaches a certain degree we have DIABETES. Diabetes is serious, womb-to-tomb unwellness. It can do bosom and blood v as diseases, sightlessness, kidney failure, nervus harm, dentition and gum jobs, and toe, pes or leg amputations. ( www.handsonhealth-sc.org Idaho 1119 ) . If we can non command diabetes can perplex gestation, and birth defects are more common in babes born to adult females who have it. Understanding digestion and insulin Most of the nutrient we eat is broke down into glucose, it is the signifier of the sugar in the blood.it is the chief fuel for the organic structure. After digestion procedure, glucose base on ballss into the blood stream, where it is used by cells for growing and energy. For glucose to acquire into the cells insulin must be present. Insulin is a endocrine produced by the pancreas, pancreas is the big secretory organ behind tummy, people with diabetes do non do insulin, or they can non utilize insulin decently, or both. This causes glucose to construct up in the blood alternatively of traveling into the cells. As a consequence people with the status frequently feel ; thirsty, hungry tired.

Case Analysis Chevrolet Europe

Case Analysis Chevrolet Europe Problem Statement The manager for brand strategy of GM addressed the Project Midas team in early 2004. The marketing team of the Project Midas had to provide â€Å"a positioning statement for the Chevrolet brand in Europe† (Kerin Peterson 644). The Project Midas had to provide the statement, but the product line of the GM Daewoo, model characteristics, prices, distribution coverage and dealers’ sales practices were to remain the same.Advertising We will write a custom case study sample on Case Analysis: Chevrolet Europe specifically for you for only $16.05 $11/page Learn More Additionally, the Project Midas team had to achieve a goal of one percent market share for the brand in the European market (Kerin Peterson 634). However, the primary objective of the Project Midas team was to make European car buyers acquainted with the Chevrolet brand. Admittedly, the marketing team had to make the brand popular (or at least known) to achieve other goa ls provided. Short Summary of the Facts Basically, the Project Midas had to make the Chevrolet brand known to Europeans as the brand was â€Å"virtually unknown† to European customers in 2004 (Kerin Peterson 649). According to research less than one percent of European customers knew the Chevrolet brand and its bowtie logo. On the other hand, Daewoo cars were quite popular in many European countries. This could be a very good foundation for the development of the appropriate strategy. Analysis of the Facts Unknown to the European car buyers In the first places, it is important to consider the fact that the Chevrolet brand was quite unknown to the European car buyers. As has been mentioned above, less than 1% of the European customers knew anything about Chevrolet. Therefore, it could be possible to create a positioning statement from scratch, i.e. the marketing team could develop a brand-new strategy to introduce the brand. On the other hand, some people could have some misc onceptions concerning the car. For instance, Europeans could think the car was not for them â€Å"due to preconceptions of American cars as gas-guzzling yank tanks† (Kerin Peterson 649). Therefore, while creating a positioning statement, it was essential to take into account this fact as well. Thus, The Project Midas marketing team did not have to adapt certain strategy to the existing portfolio of the brand (as the brand was almost unknown), but they had to debunk existing misconceptions. Positive image of the Daewoo brand Secondly, while constructing a positioning statement, the Project Midas team could exploit popularity of certain Daewoo cars. For instance, Daewoo Matiz was particularly popular in such countries as Poland, Chech Republic, Portugal and Italy. More so, according to Kerin Peterson it became the winner at â€Å"The World’s Most Beautiful Automobile of 1998† (in the segment of the small car) (644). According to research held in 2003 owners of t he Matiz (or potential buyers of this car) valued such qualities as reliability and fair price (Kerin Peterson 646). It was also found that the owners of these cars were loyal to the brand. Other preferences expressed by the European buyers of the Matiz were as follows: â€Å"peace of mind†, practicality of the car, applicability for urban settings, style and â€Å"friendly dealership personnel† (Kerin Peterson 648).Advertising Looking for case study on business economics? Let's see if we can help you! Get your first paper with 15% OFF Learn More Customer Profile Finally, it is also important to consider the customers’ profile. The European car owners can be divided into three major groups: the â€Å"Social Climber Segment† (upper middle class and middle class) represents 9% of cars owners, the â€Å"Conventional Modern/Progressive Modern Mainstream Segment† (younger middle class, above-average income) represents 18% of c ars owners, the â€Å"Counter Culture Segment† (lower class, middle class) represents 8% of cars owners (Kerin Peterson 640). Admittedly, it is quite difficult to address all the three groups. However, it is possible to cover at least two of them. It could be effective to address the latter two segments. Interestingly, Kerin Peterson provide the following customer profile of the Daewoo brand customers: unpretentious, â€Å"traditional meaning of life†, broad age range, mainly married (649). Therefore, these customers could form the target group of the new campaign aimed at introducing the Chevrolet brand. Alternatives It is possible to suggest at least three alternatives to achieve the goal mentioned above. In the first place, it is effective to use various informational channels to make people aware of the new brand. For instance, the experience of the Chevrolet brand proved to be quite effective. They provided Daewoo cars owners with corporate letters (sent via e-m ail) which announced the changes which were taking place (Hollensen 582). Therefore, loyal buyers could learn more about the changes which were taking place in the company. However, it could be more effective to use the Internet more excessively. Not only Daewoo cars buyers should be acquainted with the Chevrolet brand. It is possible to send information about the brand to buyers of various products (other cars, or even tyres). Apart from this, it is essential to take parts in various events: exhibitions, fairs, competitions. This can help to introduce the new brand to a wide audience. It can be effective to sponsor various TV programs which have the same audience as the target group of the Daewoo brand customers. This will help to raise the awareness among loyal customers of the Daewoo brand. Besides, it can be also effective to collaborate with various companies. For instance, the Chevrolet car could be a prize for the winner of some competition held by some retailing network. Thi s could be a good way to promote the new Chevrolet brand. However, it is not enough just to announce the appearance of the new brand on the European market. It can be more effective to focus on debunking misconceptions of American cars. The information channels mentioned above could be used (the Internet, TV, sponsorship, collaboration with other companies).Advertising We will write a custom case study sample on Case Analysis: Chevrolet Europe specifically for you for only $16.05 $11/page Learn More Apart from these channels, it can be effective to start an advertising campaign with new advertisement (video, pictures, brochures) available on the Internet, on TV and in print. The major focus of the campaign will be the following message: some American cars were really ‘gas-guzzling’, but at present American cars are as economical as their European counterparts. Recommendations / Solutions Thus, the major goal is to make people acquainted with th e new brand. One of the trumps of the Chevrolet in Europe is that Europeans know little about the brand itself, but they have certain misconceptions concerning American cars. It can be effective to note that even though this misconception was true in the past, now things have changed. The advertising campaign should communicate the following messages: American cars were ‘gas-guzzling’ before the 2000s; American car producers (the Chevrolet brand in particular) now address environmental concerns; American car producers (the Chevrolet brand in particular) address issues concerning gas and financial crises; The Chevrolet brand is aware of the European customers’ needs; The Chevrolet brand strives for meeting the European customers’ needs. Admittedly, such attention to the needs of the customers will create a positive image of the company and the new brand. Negative emotions are believed to be stronger than positive ones. Therefore, information based on nega tive emotions can be more memorable and credible. Of course, it is important to ‘convert’ negative things in highly positive. Thus, it can be effective to contrast some conventional American cars with the new Chevrolet brand cars. It is also important to explain why the American manufacturer chooses the new concepts. The European customers should get the answer to the questions: Why Americans have chosen Daewoo? Can this American brand be suitable for Europeans? Besides, it is essential to make people understand that all the qualities valued in the Daewoo brand will be present in the Chevrolet brand. It is important to remember that Daewoo Matiz cars have been really popular in Europe. For instance, in 2002, more than 132,000 units were sold in Europe (Kerin Peterson 644). Therefore, it is necessary to use this popularity. It is possible to communicate the idea of high quality. Again, it is important to make customers think of American cars’ quality. It is possi ble to communicate the following message: the popular European car was approved by the American car manufacturer. Admittedly, world recognition will increase the brand’s value.Advertising Looking for case study on business economics? Let's see if we can help you! Get your first paper with 15% OFF Learn More As far as information channels are concerned, it is possible to make the major focus on the Internet which has become one of the central information channel. People are extensively using the Internet which is often associated with innovations and progressiveness. This is a very good channel to introduce the new modern car brand. Hollensen, Svend. Global Marketing: A Decision-Oriented Approach. Harlow, Essex: Pearson Education, 2007. Kerin, Roger and Robert Peterson. Strategic Marketing Problems: Cases and Comments. Lebanon, Indiana: Prentice Hall, 2009.

How to Write When Muse Doesnt Help

How to Write When Muse Doesnt Help There you are. Slamming your brain repeatedly against the keyboard at 1:53am while your loudest â€Å"make ideas happen† music blares from your headphones. Intermittently, you are uploading pictures of your cat to Instagram while cursing the professor who assigned this stupid essay. You are considering selling your soul to the Devil in lieu of a working thesis statement. Don’t make any blood oaths just yet. Even when your brain just doesn’t seem to be making any connections, there are ways to get your ideas flowing and that essay started. With a little creative help and a lot of determination, even the most uninspired essay can turn into a gem. 1. Go Where the People Are In a recent study from the University of Illinois at Urbana-Champaign, researchers found that ambient noise at around 70 decibels actually improves creative thought. They found that extreme quiet, 50 decibels or lower, impedes the ability to think abstractly since it introduces too much focus into the equation. On the other hand, make sure you don’t go where there is too much noise. The study also showed that noises over 85 decibels, the sound of heavy traffic, is too distracting for creative thinking. So, make sure you go to a coffee shop, not a metal concert. 2. Create an Outline Remember in high school when your teacher forced you to make an outline? It might have seemed like a huge waste of time then, but it’s a great trick to get your essay on the page. In fact, with a good enough outline, half of your paper will already be written for you. In fact, there is a simple 7-step procedure to have an excellent outline that will always get you off to a good essay start. Answer the prompt. In one or two sentences, answer the prompt for the article. This is your thesis statement. It will go at the end of your first paragraph. Write a main sentence for each of your paragraphs. Each paragraph should help to explain what you stated in your thesis. For each paragraph, write one sentence about what that paragraph is going to say. List 2-3 resources for each paragraph. Look at the main sentence for each paragraph. Now, find some resources that prove what you said in that sentence. List them. Now that you have all your paragraphs and thesis statement outlined, you will have some great ideas on how to start writing your essay. By the time you’re finished writing the body, or â€Å"meat,† of your essay, you should have some good ideas on how to write the introduction and conclusion. 3. Set a Timer One of the best ways to get writing when your brain feels like mush is to do a timed writing. Simply set your timer for 5-10 minutes and sit down at your computer. Start writing whatever comes into your head. If you’re working on an essay, write down all the things you know about the subject, or how you feel about it. Whatever you do, don’t stop writing. When you run out of things to say, simply write, â€Å"I don’t know what to say.† Your brain will eventually fill that space with things that can help you connect your ideas with the essay you need to complete. 4. Do Some Research I don’t mean search â€Å"funny cat videos† for two hours. I mean, real research. For example, if your essay needs to be about a current event, go to an online news source and start looking at headlines. Anything that catches your attention is a great place to begin your research. Especially if you’re low on time, research is another area where it’s a good idea to time yourself. Set the clock for one hour and look for concrete evidence to support your ideas. Educational websites (.edu) and governmental websites (.gov) are the most authoritative, so their excellent places to start. Also, make sure that you are citing your source so that you don’t get in trouble for plagiarism. 5. Just Write It In the end, writing an essay is simply about sitting down and doing it. Many authors, essayists, and professional writers don’t wait for inspiration before they put pen to paper. As a student, you can’t wait until inspiration strikes to start your essay. Simply setting aside a time to write and then making it happen is the best way to avoid losing your soul to a college essay assignment.

What were the major historical causes for the successive waves of Essay

What were the major historical causes for the successive waves of Greek colonization In what ways did Greek colonies impact Greek political institutions and cultural values - Essay Example Moreover, years of military expertise and familiarity with defending the Greek Speaking world from a host of foreign threats came to integrate deeply within an understanding of Greece and its role throughout the region. As can be seen from the situation that is been described, there was not merely one or two factors that encourage to Greece to colonize and otherwise invade the surrounding regions. Instead, a litany of factors coalesced and encouraged the nascent state, as a direct result of its exposure, trade, and subsequent military conquest, that colonization would be an effective means through which a greater level of wealth and regional influence could be exhibited. After the conquest of the first wave of Greek colonization, it became clear that a level of administrative authority, unlike what existed within the Greek states, must be exerted as a means of ensuring that a level of separatism and possible/potential rebellion was not exhibited. Due to the fact that the individuals who were colonized were inherently â€Å"non-Greek† the colonies could not be expected to be administered willingly in the same way that free men within the Greek city states existed. As such, a new form of administration and one that promoted a level of Greek culture, identification, and governance was established within these newly conquered realms. Although it was not a primary interest of the Greek colonizers to instill a level of cultural respect, the institutions and governance structure that was established effectively created a level of Greek culture and respect for it within the institutions that have thus far been described. As with any empire throughout the course of history, the growth and diversity of colonies created a situation in which Greece was forced to expend a great deal of energy, time, and money as a means of administering and ensuring that these colonies continue

Organizational Behaviour Essay Example | Topics and Well Written Essays - 1250 words

Organizational Behaviour - Essay Example The happier an individual is within their job, the more satisfied they are said to be. Job satisfaction is not the same as motivation, although it is clearly linked. Job design aims to enhance job satisfaction and performance, methods include job rotation, job enlargement and job enrichment. Other influences on satisfaction include the management style and culture, employee involvement, empowerment and autonomous work groups. Job satisfaction is a very important attitude which is frequently measured by organisations. The most common way of measurement is the use of rating scales where employees report their reactions to their jobs. Questions relate to rate of pay, work responsibilies, variety of tasks, promotional opportunities the work itself and co-workers. Current paper provides comparatative analysis of five articles about job satisfaction as well as reports research on two additional articles. Basically there are 7 sources that alltogether provide a good overview on the issue. Job satisfaction is in regard to ones feelings or state-of-mind regarding the nature of their work. Job satisfaction can be influenced by a variety of factors, eg, the quality of ones relationship with their supervisor, the quality of the physical environment in which they work, degree of fulfillment in their work, etc. In the articles of Joseph E. Gawel â€Å"Herzbergs theory of motivation and Maslows hierarchy of needs† the author describes two behavioral theories that were long generally believed and embraced by business – the one of Frederick Herzberg and Abraham Maslow. Herzberg, a psychologist, proposed a theory about job factors that motivate employees. Maslow, a behavioral scientist and contemporary of Herzbergs, developed a theory about the rank and satisfaction of various human needs and how people pursue these needs. These theories are widely cited in