The surface was treated with chrome plating and riveted or welded with the frame rails. The large gap, as if it were an attached part, looks very unattractive. With the development of the automotive industry and the extensive application of engineering plastics in the automotive industry, automotive bumpers has also entered the path of innovation as an important safety device. At present, in addition to maintaining the original protection function, the front and rear bumpers of the car must pursue harmony and unity with the shape of the car body, and pursue its own lightweight. The front and rear bumpers of the car are made of plastic and are known as plastic bumpers.
Automobile bumper industry standards meet the requirements of national mandatory laws and standards.
1.2 Problem statement
Nowadays, every country around the world is facing increasingly serious car accident, and the frequency of happen was increasing every year. A car accident can happen to everyone, whether you are a pedestrian or a motorist. Based on the statistical data from the report by TRANSPORT STATISTICS MALAYSIA, in the past ten years, number of car accidents have increased every year in Malaysia (refer to the below table 1.2.1). (STATISTIK PENGANGKUTAN MALAYSIA TRANSPORT STATISTICS MALAYSIA 2017 KEMENTERIAN PENGANGKUTAN MINISTRY OF TRANSPORT MALAYSIA, n.d.)
(Table 1.2.1: Statistic for the number of car accidents and death)
Year Total Number of Accidents Death
2008 373071 6527
2009 397330 6745
2010 414421 6872
2011 449040 6877
2012 462423 6917
2013 477204 6915
To be both aesthetically and practically, car bumper that made in plastic is the best choice for current technology. But in this advanced era, the cost of manufacturing the parts of car bumper is still very high. It is also very expensive for replacement, particularly the surface area or the part is burst or cracked. Car bumpers are made from a variety of materials and various processes",it is involved to a lots of stages. However, the manufacturer of the automotive industry difficult to reduce the cost for manufacturing the part of the car bumper. Manufacturer also receive pretty much of complain about the car bumper easily to get damaged although the car bumper is subjected to a slight impart. To improve the performance of the car bumper, like the impact resistance of the bumper, to research the alternative material and the design of the car bumper should be consider priority.
• Design the generic front bumper using AUTODESK INVENTOR 2015 including the improvement that suitable to be made increase the performance of the bumper. The design that were analysed using stimulation analysis method to study the toughness of the bumper design by performing the impact test.
• To emphasize the improvement and cost reduction aspect of the designed bumper including the beam design.
National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS) which are the place to do the crash test is always a good platform to test the toughness of car bumper. When an accident is happened, firstly peoples will thought about the toughness of the front bumper or rear bumper of the car, whether it is enough tank which is related to the design and the material of the car bumper. In order to achieve the better record for toughness of the car bumper, an innovative design and better material replacement must be considered priority. That is the reason why I always interested the production of the car bumper. Every automotive industry will send their new models car to NHTSA to do the crash test whether it is able to certify their product to satisfy Federal Motor Vehicle Safety Standards (FMVSS). In this advanced era, the most tank car which is awarded in the world is Lexus branded car which is made in Japan. This brand has achieved the best record of the crash test in NHTSA. However, the reliability and the competition between the automotive industries is much more crucial than unadulterated pace. Different materials and design can result the level of the toughness of the car bumper. The design of the car bumper such as the thickness, curvature, shaping, size of the car bumper all can affect performance. In motivation, to manufacture a low cost, aesthetically and practically car bumper are the goal for every each automotive industry.
1.5 Project Aim
The main goal for this project is to design a car bumper for the car that has better impact resistance and low cost while the toughness of the safety meet the requirement of Federal Motor Vehicle Safety Standards (FMVSS).
1.6 Thesis Overview
First things first, the project will begin by referring the application front car bumper and rear bumper of the car. Another than that, due to some research I had go through, I had make sure enough knowledge considering stress analysis is learnt. Because the basis of this project is about to design a new car bumper for the car, Autodesk inventor 2015 version is required to create this part. Stress analysis from the Autodesk inventor 2015 will be used for test the few concept design of the car bumper and also some relevant calculation to prove actually they are work and deserve the result. The best design will be picked, it is depend on their performance for every each design. Every doubt considering this subject will be discussed with my supervisor.
Chapter 2: Literature Review
Every car manufacturer is focused on the safety of the car, this become their main concern to manufacture every each car. Other than the improvement of drive train performance, safety of the car is the main aspect worthy of attention. In order to persuaded the clients that the vehicles are regarding safety enough to be drive. Within this chapter, will give detail description of literature review done by the project title of design and fabrication of car bumper. The car bumper is a key safety part that absorbs and mitigates external impact and protects the front and rear of the car body. It is also a vehicle guard made of plastic, steel, and aluminium that is installed on the front and rear of a car. When the car collides at low speed, the front bumper can absorb the impact energy to reduce physically damage to the car. Therefore, it is necessary to study the collision characteristics of the bumper and the energy absorption characteristics during the collision. The main purpose to design a car bumper is to absorb and mitigates the external impact to the car, protects the body and the safety of the driver. For the driver, the role of the car bumper is important, the role of the car bumper is not only the decorative effect. This chapter consists of brief discussions regarding to current automotive safety technology including any existing technology or on going research.
2.2 Active Safety System In Market
Regarding to automotive safety, car accidents are caused by many factors. Car bumper has become the main part in active safety system to against the impact. The purpose of active safety system is to develop a road traffic system that can better handles human error and takes into account human vulnerability. The starting point is the acceptance of mistakes and the recognition that traffic accidents cannot be completely avoided. The goal of the safety system is to ensure that the accident does not causes serious personal injury. Car bumper is the main part to reduce the physical damage to the car body that deal with active safety system. There are two main types of automotive safety systems: active safety systems and passive safety systems. The active safety system are ABS (anti breaking system) and ESP (Electronic Stability Program). The passive safety system involves the car bumper, safety belt, airbag, and etc. Today, active safety system frontier technology has developed into a pre-crash safety system, the most typical of which is the active braking system (refer to figure 2.2.1). (Azri Azlan, n.d.) (“10 Top New Cars with Active Safety Systems | Autobytel.com",” n.d.)
2.3 Types of car bumpers
Car come mounted with few types of bumpers. The type of bumper with the car can influence what trailer hitches will fit. The following are the five kinds of the car bumper the car normally could have in the market. Refer to table (2.3.1) (“Types of Bumpers | etrailer.com",” n.d.)
Types of Car Bumper Name of Bumper Description
Normally every sedan car could have.
Deep Drop Bumper
Normally mounted on older truck and is generally chrome covered. This bumper own heavy duty towing limit.
Roll Pan Bumper
Normally mounted on custom reduced truck. The trailer hitches accessible will sit in the center, behind the bumper.
Normally mounted on vans and SUVs. The little platform in the middle resembles a stage to step on. The bumper has gaps to use to tow lightweight trailers.
Normally this bumper mounted on jeeps.
2.4 Structure of Front Car Bumper System
A car bumper is mounted to front and rear of the car to absorb the impact in a crash，therefore, ensuring the safety of traveller. As the following figure (2.4.1) shown below, a structure of car bumper composite with bumper cover 1 which is external appearance of the bumper system. 2 is defined as energy absorber composited of an elastic material such as Polyurethane to absorb impact, the bumper beam 3 for supporting the energy absorber 2. The part 4 is for connecting the impact beam 3 to the car body. By then, when composite on an upper or lower end of the bumper beam to improve the performance, those part which are bumper cover 1 and energy absorber 2 might be damage when the mounting space is not adequate.(Firdaus, 2008)
2.5 Bumper Beam
The bumper beam is the foundation which able to absorb energy. It can be situated in the front car body, and can be in the rear, sides of the car body. Regarding to safety of the passenger, front system have to be stronger than back system. Then again, bumper design focus more on aerodynamic efficiency . In fact, the designed curved of the bumper beam should prior to considered. Along these line, the composite material has solve this dilemma by giving the required curvature and bringing down the assembling cost by multi arrange stepping of the steel bumper beam, and reducing the weight of the bumper beam.(Davoodi et al., 2012)
2.6 Criteria of the Car Bumper
Every standard car must be mounted with a car bumper. The main two factors for the regulations have to be apply for automobile bumpers is to protected the front and rear body and it can play a role in protecting pedestrians in the event of an accident with pedestrians. The standard of the bumper was prescribed performance needed for traveler vehicles in low-speed front and back crashes. According to international safety regulations which is initially set up as European standard under the manipulation of the United Nations, most of the country around the world are adopted this criteria as their standard. These criteria determine that a car bumper still working properly and still can maintain a good condition after the front and the rear bumper has sustain the moving-barrier impact of 4km/h (2.5mph) (refer to figure 2.6.1), and to the front and rear corners of 2.5 km/h (1.6 mph) at 45.5 cm (18 in) above the ground with the loaded car and unloaded car. There is some of the vehicle that does not need a solid bumper over the vehicle, but satisfy the standard by deliberately mounted bumper and corner bumper. (United Nations ECE Regulation No. 42: Uniform Provisions Concerning the Approval of Vehicles With Regard to Their Front and Rear Protective Devices (Bumpers, etc.), 1980) (“Federal Bumper Standards | Receiver Hitch Step that helps eliminate rear end collision damage | shock absorbing hitch step | Superbumper | Bumper Shield",” n.d.)
As the figure (2.6.1) above shown that, the bumper of the car with white in colour able to withstand the impact with its speed crashed with parked cars.
2.6.2 The Attribute of a Good Bumper
Regarding to stability and energy absorption of the car bumper. car Bumpers on impacting vehicles should arrange geometrically with the goal that they connect each other when facing a low-speed collide to absorb collide energy. The bumpers should cover each sufficiently other to represent varieties in ride height and preimpact braking, which can lower the front end or raise the rear end of a vehicle just before impact. Bumpers should stay engaged with the other bumpers in collisions instead of overriding or underriding them, which frequently results in damage to vehicle grilles, headlights, hoods, fenders and trunks. Bumpers ought to have adequate capacity of energy absorb to limit damage to the bumper system itself.
Past of this these basic attributes, a bumper that has good performance has reach out to the edge of vehicles to protect headlamps and fenders.. (VILLAGE AUTO BODY INC, n.d.)
2.7 Selection of Materials for a Car Bumper
The following are the materials usually car bumper made of, able to perform high performance with its impact resistance. (“What Materials are Used for a Automobile Bumpers | First Choice Reconditioning",” n.d.)
Polypropylene is a thermoplastic polymer used in a wide variety of applications. A saturated addition polymer made from the monomer propylene, it is rugged and unusually resistant to many chemical solvents, bases and acids.
Solid Polyurethane is an elastomeric material of exceptional physical properties including toughness, flexibility, and resistance to abrasion and temperature. Polyurethane has a broad hardness range, from eraser soft to bowling ball hard. Other polyurethane characteristics include extremely high flex-life, high load-bearing capacity and outstanding resistance to weather, ozone, radiation, oil, gasoline and most solvents.
Nylon 6/6 is a general-purpose nylon that can be both molded and extruded. Nylon 6/6 has good mechanical properties and wear resistance. It is frequently used when a low cost, high mechanical strength, rigid and stable material is required. Nylon is highly water absorbent and will swell in watery environments.
high performance plasticsAmorphous polycarbonate polymer offers a unique combination of stiffness, hardness and toughness. It exhibits excellent weathering, creep, impact, optical, electrical and thermal properties. Because of its extraordinary impact strength, it is the material for car bumpers, helmets of all kinds and bullet-proof glass substitutes.
2.8 Characteristic of Materials
1. Polypropylene (PP)
It has low density, high stiffness, heat resistance, chemical inertness, and good impact balance. (“Poly(propene) (Polypropylene)",” n.d.) (youssef mobarak, n.d.)
Density /kgm-3 905
Tensile Strength /Mpa 33
Tensile Modulus /Gpa 1.4
Elongation at Break /% 150
Thermal conductivity W/(m*K) 0.22
Polyurethane performs well for hardness, tensile strength, compression strength",impact resistance, abrasion resistance and tear strength. (“Polyurethane Properties",” n.d.) (Kun, n.d.)
Density /kgm-3 1125
Tensile Strength /Mpa 18
Tensile Modulus /Gpa 1.0
Elongation at Break /% 100
Thermal conductivity W/(m*K) 0.28
It is high wear resistance, high thermal stability, very good strength and hardness, high mechanical damping characteristic, good sliding properties, and good chemical resistance. (“PA Polyamide Nylon - TECAMID | Ensinger",” n.d.) (“Nylons (Polyamide)",” n.d.)
Density /kgm-3 1114
Tensile Strength /Mpa 100
Tensile Modulus /Gpa 2.95
Elongation at Break /% 60
Thermal conductivity W/(m*K) 0.25
It is tough, transparent engineering thermoplastic which offers very high impact strength and high modulus of elasticity. (Serini, 2000) (Inc, n.d.)
Density /kgm-3 1200
Tensile Strength /Mpa 65
Tensile Modulus /Gpa 2.2
Elongation at Break /% 110
Thermal conductivity W/(m*K) 0.20
2.9 Importance of Design Parameter of Car Bumper
Bumper is a front most part of vehicle, it keeps passengers and other parts of vehicle are safe. During impact parameters affected on bumper performance such as speed of vehicle, mass and time of impact. While taking example of one of the car manufacture, design parameter such and thickness and material properties are studied. Comparative analysis of various materials is done with original steel material by FMVSS (Federal Motor Vehicle Safety Standard). Results show that mass, speed and impact time play important role, as these changes it affected on vehicle during accident. As thickness of bumper increase its deformation reduces but weight of bumper increase, present steel material possible to replace with low density material. It is important that focus of selecting bumper material, if focus is safety then sometimes compromise with weight and light weightiness. If the focus is light weight bumper then compromised with safety and strength. (IJARTET, n.d.)
2.10 NEWTONS LAW
In an accident like car crash, newton’s second law is applied to study the force exerted of car bumper that is being crashed. It says that when an object in motion encounters some kind of force, its direction and speed, also known as its momentum, will change in the direction from which the force is applied. In addition, the change in momentum is inversely proportional to the object’s mass. This means that with a given force, the smaller the object’s mass, the greater the change in momentum, and the greater it’s mass, the less its momentum will change. This method applicable to all vehicles in order to find force generated after impact BY NEWTONS LAW (f=MA) this condition is applicable only when vehicle hit one at the same. For example, a car moving at a speed of 20m/s2 and its mass is 1000kg, formula which is F=MA will be applied to find the force exerted after impact, the exerted force is 200Kn from the car of the impact. (Quinten Kenrick, n.d.)