Composite Material in Car Hood
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Composite material in car hood Investigation of possible sandwich materials Kompositmaterial i bilmotorhuv Johan Karlsson Faculty of Health, science and Technology Degree project for master of science in engineering, mechanical engineering 30 credit points Supervisor: Christer Burman Examiner: Jens Bergström Date: Spring semester 2016, 2016-09-01 Abstract In the car industry today, one of the things that the highest focus is on is the fuel consumption of the car and the emissions from the car. This is because the environmental rules becomes tougher and tougher, and with lower fuel consumption and emission the cars damage the environment less. There are many ways to lower these parameters, one is to lower the total weight of the car, by lowering the mass of the different parts of the car leads to a lower total weight. Especially in the front of the vehicle is very important in Volvos goal to making cars. By introducing composite material to the hood, there are possibilities to make a hood with the same properties but with a lower mass. By using different methods to investigate competitors, demands & re- quirements, properties and material structures, the materials goes from a lot of material to just a few. From this investigation, the results finally ended with two types of mate- rials that theoretically can be used in the car hood. These lowers the mass, and still fulfill the hoods requirements and demands. The results showed that a hood with a PVC or SAN cored sandwich structure with aluminum face have the right properties to be used in a new car hood. Sammanfattning Inom bilindustrin ¨aren av de saker som har h¨ogstfokus just nu ¨arbilens br¨anslef¨orbrukningoch utsl¨appen fr˚anbilen. Detta beror p˚aatt milj¨oregler blir allt h˚ardareoch h˚ardare,och med l¨agrebr¨anslef¨orbrukningoch utsl¨app fr˚anbilarna leder det till mindre skador p˚amilj¨on. Det finns m˚angas¨attatt s¨anka dessa parametrar, ett ¨aratt s¨anka bilens totala vikt, genom att s¨anka massan av olika mindre delar, leder det till en l¨agretotal vikt p˚abilen. I Volvos m˚alatt tillverka bilar, ¨ardet speciellt viktigt att s¨anka vikten i fronten pga att motorn sitter fram och d¨arf¨orredan har h¨ogmassa. Genom att introducera kompositmaterialet till huven, finns m¨ojlighetenatt tillverka en motorhuv med samma egenskaper men med l¨agre massa. Genom att anv¨andaolika metoder f¨oratt unders¨oka konkurrenter, krav, egenskaper och materialstrukturer, g˚aralternativen fr˚analla material till bara n˚agraf˚am¨ojliga. Fr˚andenna unders¨oknings˚astod resultaten till slut mellan tv˚atyper av material som teoretiskt kan anv¨andasi en bilhuv som i sin tur ¨aven s¨anker massa och uppfyller huvens krav innom de ramar som var satta. Resultaten visade att en huv med en PVC eller SAN skummk¨arnaoch aluminium som facematerial har de r¨attaegenskaperna f¨oren ny motorhuv. Contents 1 Introduction 8 1.1 Background . .8 1.2 Purpose . .8 1.3 Aim . .9 1.4 Limitations . .9 2 Method 10 2.1 Technical Regulation . 10 2.2 Technical Regulation, Car Hood . 10 2.2.1 Function . 10 2.2.2 Function Determining Properties . 11 2.2.3 Properties Over Time . 11 2.2.4 Manufacturing Properties . 12 2.2.5 Araesthetical Properties . 13 2.2.6 Legal Demands . 13 2.3 Work process . 14 2.4 Benchmarking . 15 2.4.1 BMW i3 . 17 2.4.2 Renault Twingo . 18 2.4.3 Aston Martin V12 Vanquish . 19 2.4.4 Porsche 911 R . 20 2.4.5 Ford Focus . 21 3 3 Theoretical Background 22 3.1 Hood Section . 22 3.2 Hood Complete . 22 3.3 Hood Geometry . 23 3.4 Pedestrian Protection . 24 3.4.1 Background . 24 3.4.2 Head Impact Test . 25 3.5 Upper Leg Test . 28 3.5.1 Conflicting Vehicle Requirements . 29 3.6 Volvo Cars Hood Demands[1] . 30 3.6.1 Passive Safety . 30 3.6.2 Safety Requirement Pedestrian . 31 3.7 Safety Requirement Latches And Hinges Integrity . 32 3.7.1 Hood Hinges . 32 3.7.2 Hood Latches . 32 3.7.3 Test Method . 32 3.8 Safety Requirement Low speed . 33 3.8.1 Low speed damage . 33 3.8.2 Strength & Endurance . 33 3.9 Overopening Of Hood, Strength . 33 3.10 Sandwich Core Structures . 34 3.10.1 Background . 34 3.10.2 Core Types . 37 3.10.3 Face Material . 40 3.10.4 Adhesives . 41 4 4 Results 43 4.1 Benchmarking . 44 4.2 Demands & Requirements . 47 4.3 Changeable Parameters . 48 4.4 Material Structure . 49 4.4.1 Core . 49 4.4.2 Face . 52 4.5 Final Results . 54 4.5.1 Face . 54 4.5.2 Core . 55 5 Discussion 57 5.1 Future work . 60 5.1.1 Physical tests . 60 5.1.2 Simulations . 61 5.1.3 Demands . 61 6 Conclusions 61 Appendix A Technical Regulation 66 Appendix B Material Data 70 Appendix C MatLab,bending stiffness 71 5 List of Figures 1 BMW i3. 17 2 Renault Twingo. 18 3 Shows the carbon fiber inner hood of the Aston Martin V12 Vanquish. 19 4 Shows the carbon fiber hood of the new Porsche 911 R. 20 5 Ford Focus with a foam core material sandwiched between two layers of carbon fiber reinforced polymer . 21 6 Inner hood geometry [1] . 24 7 Head impact [2] . 25 9 Upper leg impact test [2] . 28 10 Barrier collision test . 30 11 Volvo FKB [1] . 31 12 Bending of Sandwich beam [3] . 36 13 Foam core . 37 14 Honeycomb core . 39 15 EuroNcap pedestrian results for the BMW i3 [4] . 45 16 EuroNcap pedestrian results for the Renault Twingo [4] . 45 17 EuroNcap pedestrian results for the Volvo XC90 [4] . 46 18 EuroNcap pedestrian results for the Volvo V60 [4] . 46 19 Chart of parameters that influence the total mass of the hood 48 20 An example of structural efficiency of sandwich panels in terms of weight [5]. 50 21 Bending locations of the Volvo car hood. 51 6 22 Aluminum Alloy used in the hoods today [1]. 55 23 Properties of SAN-foam with different density [6]. 59 24 Properties of PVC-foam with different density [7]. 59 List of Tables 1 Demands and depending material properties . 48 2 Bending Stiffness results with different core thickness . 53 3 Material data polymers . 70 7 1 Introduction 1.1 Background Weight reduction of cars and especially in the front of the vehicle are very important in Volvos goal to make cars with low fuel consumption and low emissions. The exhaust emissions emitted from a passenger car has for the last decades been recognized as a major negative impact factor on the envi- ronment. Due to this, the legislation on exhaust emissions are getting more and more stringent. Volvo want to investigate the possibilities by introduc- ing composite material in their hoods to save weight and improve properties. To do this improved knowledge in the area is needed, new thinking and a new technical solution must be found. Taking in consideration all demands of the complete hood system today. Start up from Volvos knowledge today regarding composite and hang on parts, develop and increase knowledge. 1.2 Purpose The purpose of this thesis work is to investigate if it is possible to introduce a sandwich material in the hood of the car. The hood has a lot of demands and rules, in form of pedestrian protection, durability, stiffness and so on, that have to be fulfilled for an approved hood. 8 1.3 Aim The aim with this thesis is to reach a first step in this investigation about a new material for the car hood. The new material needs to match Volvos demands and requirements and lower the weight of the car hood, which leads to lower fuel consumption and a more environmentally friendly car. 1.4 Limitations This project includes: • Is it possible to make a hybrid composite hood? • What are the different composite materials? Does it exists any other solutions than fiber composites? • How to structurally design the hood to make it weak in some places and strong in others, considering controllable deformation in high speed crash. • Benchmarking and competitor analysis • Pedestrian protection, Head impact • Overall stiffness Things that are not included: • Surface quality • How the new hood material is adapting to today's manufacturing plant • Corrosion protection of these new materials 9 2 Method 2.1 Technical Regulation A technical regulation is established before it is possible to carry out larger construction project. In appendix A one can find a functional template, taken from an other earlier Volvo project, that shows different topics that can be followed to create a good technical regulation. Below is the development of a technical regulation for a car hood, and the content of this has a large influence on this investigation. Using Apendix A as a template. 2.2 Technical Regulation, Car Hood 2.2.1 Function What is the purpose of the product, what is the task? Reduce damage of pedestrian considering head impact, associated with low- speed crash with pedestrian. Protect the underlying parts and the motor from theft, also to take away the ability to disable the car alarm. Protect parts under the hood from environmental damage, like corrosion and water. Give the car better aerodynamics and a good look with styling. 10 2.2.2 Function Determining Properties What performance shall the product fulfill? Weight: lower than the current mass of the hood, which is 10 kg. Tempera- ture: withstand temperatures in the range of -30 to 100◦C.