POLYMER COMPOSITE SANDWICH CONSTRUCTION IN AUTOMOBILE TO ENSURE SAFETY

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November2018, pp , Article ID: IJMET_09_11_095 Available online at ISSN Print: andISSN Online: IAEMEPublication Scopus Indexed POLYMER COMPOSITE SANDWICH CONSTRUCTION IN AUTOMOBILE TO ENSURE SAFETY C Anil Kumar Reddy Department Of Mechanical Engineering,PRRM Engineering College,Hyderabad ABSTRACT Passenger s safety is the most important aspect to be taken care of while designing automobiles parts. The parts are so designed that the product is light in weight, economical as well as strong enough to take up sudden shocks while the vehicle is met with an accident. When a vehicle is hit from rear or front, the part that gets affected is the crash bumper which them protects the chassis of the vehicle from getting damaged. So, bumper should be strong enough to take up the shock loads and prevent itself from getting crashed. The passenger safety is a paramount in automobile design. Polymer composites could successfully meet the demands of designer. The metallic body automobiles have disadvantages during collision; the impact energy of collision will transferred to passengers which lead to fatality. We have made an attempt to design, model and analyze the bumper under static loading conditions Better materials were used while modifying design to increase in strength Keywords: automobile safety; composite sandwich construction; composites in automobiles; polymer composites; sandwich construction; Cite this Article: C Anil Kumar Reddy, Polymer Composite Sandwich Construction in Automobile to Ensure Safety, International Journal of Mechanical Engineering and Technology, 9(11), 2018, pp INTRODUCTION Composites are one of the most widely used materials because of their adaptability to different situations and the relative ease of combination with other materials to serve specific purposes and exhibit desirable properties. In surface transportation, reinforced plastics are the kind of composites used because of their huge size. They provide ample scope and receptiveness to design changes, materials and processes. The strength-weight ratio is higher than other materials. Their stiffness and cost effectiveness offered, apart from easy availability of raw materials, make them the obvious choice for applications in surface transportation. In heavy transport vehicles, the composites are used in processing of component parts with cost effectiveness. Good reproductively and resilience handling by semi-skilled workers are the basic requirements of a good composite material. While the costs of achieving advanced editor@iaeme.com

2 Polymer Composite Sandwich Construction in Automobile to Ensure Safety composites may not justify the savings obtained in terms of weight vis-a-vis vehicle production, carbon fibers reinforced epoxies have been used in racing cars and recently for the safety of cars. Polyester resin with suitable fillers and reinforcements were the first applications of composites in road transportation. The choice was dictated by properties like low cost, ease in designing and production of functional parts etc. Using a variety of reinforcements, polyester has continued to be used in improving the system and other applications. However there are opportunities for advanced composites in specific components in the commercial automotive sector. In specialty vehicles of several types, produced in small numbers advanced composite materials have an opportunity to demonstrate their performance benefits, apart from the requirements of the competitive marketplace. The composite industry worldwide is investing in process improvements for the moulding of polymer composites using forms of conventional E-glass in mid-level performance resins, both Thermoplastic and Thermoset. Automobiles segment of composites accounts for about 50% of the thermoplastic and 24% of the thermoset composite market in the world. Glassreinforced thermoplastic polymer is a promising material for weight reduction because of the relatively low cost of the fibre, its fast cycle time and its ability to facilitate parts integration. Carbon fibre reinforced polymer is another candidate but will require breakthroughs in cost and manufacturing techniques to be cost effective for high volume production. Though not much progress has been made in India towards product development efforts, this area merits attention and holds a lot of promise. The prospects of export of composites currently are low because India does not enjoy any comparative advantage either in raw materials or in processing costs OBJECTIVES Passenger s safety is the most important aspect to be taken care of while designing automobiles parts. The parts are so designed that the product is light in weight, economical as well as strong enough to take up sudden shocks while the vehicle is met with an accident. When a vehicle is hit from rear or front, the part that gets affected is the crash bumper which them protects the chassis of the vehicle from getting damaged. So, bumper should be strong enough to take up the shock loads and prevent itself from getting crashed EXISTING SYSTEM A bumper is usually a metal bar or beam, attached the vehicle's front-most and rear-most ends, designed to absorb impact in a collision. Regulations for automobile bumpers have been implemented to allow the car to sustain a low-speed impact without damage to the vehicle's safety systems. The metallic constructions of automobile body and other components are at a disadvantage during crashing in view of passenger safety, this is because, and the impact energy of collision will be transferred to passengers which lead to fatality. So required design should be avoid above problems 1.3. PROPOSED SYSTEM The earlier designs of bumper were bulky though robust because of metallic structures. FRP is not only light weight but also strong enough and provides flexibility of design. A further step towards improvement of the bumper design would be introduction of an energy absorbing material by using sandwich construction. The temperature stable foam, can serve as the core material. Sandwich construction can be applied by modifying the cross section on such a way that the solid FRP block is replaced by foam at the centre and 4 thin FRP sheets (of about 1mm thickness) enclosing it from all four sides editor@iaeme.com

3 C Anil Kumar Reddy 2. SANDWICH CONSTRUCTION Fiber reinforced polymer sandwich construction consists of foam core between two skins of composites laminates. The thickness of the skin will be kept generally very low of the order of few mm and the core thickness will kept deeper of few tens of times the skin thickness. The anisotropic nature of fiber reinforced composite material creates a unique opportunity of tailoring the properties according to the functional requirements. Sandwich construction technique further enhances the liability of reinforced composite components to absorb more impact energy. Figure 1 sandwich construction Figure 2 cross sectional view of bumper with sandwich construction 2.1. DESIGN METHODOLOGY OF SANDWICH CONSTRUCTION A sandwich composite is constructed by sandwiching foam core between two skins of FRP laminations. The thickness of the skin ts, is kept few mm, and thickness of the core tc will be kept more deeper. The core material is formed to reduce its density. As tc is deep (tc>>ts) the area moment of inertia of the cross section is enhanced to a greater extent, due to this the flexural rigidity of sandwich construction increases to many folds FLEXURAL RIGIDITY ESTIMATIONS OF SANDWICH CONSTRUCTIONS The flexural rigidity D of the sandwich beam is the sum of flexural rigidities of the skin Ds & the core Dc respectively. The flexural rigidity of a beam is expressed by the product of young s modulus E of the material used and its area moment of inertia I. D= EI= Ds+Dc =EsIs + EcIc for four skins Where Es & Ec are the young s modulus of skin & core respectively. Where Is & Ic are the area moment of inertia of skin and core. Whereas from fig.2, for rectangular cross section of the skin. Is = 2 (bts3/12 + btsd2) Ic = btc3/ editor@iaeme.com

4 Polymer Composite Sandwich Construction in Automobile to Ensure Safety B= width of the beam Tc = core thickness. Ts =skin thickness D = (Tc+2ts)/ MANUFACTURING PROCESS USED The sandwich crash bumper manufacturing process consists of many activities such as wooden pattern making, mould making, skin moulding, filling foam and closing the bottom skin of the component. Wooden pattern making: Wooden pattern is fabricated from plywood sheets as per required dimensions. The pattern surface finish is then improved by applying nitro cellulose putty. Mould making: A simple hand lay up technique is employed to make the FRP mould from the wooden pattern. The material used is glass chopped strand-mat and commercial grade polyester resin, the mould thickness being kept around 4mm. Skin moulding: The FRP mould made from the pattern is used to mould the fiber skin by simple hand lay-up method. The skin thickness is maintained approximately 1mm by using chopped strand mat of 450 gm/m3 density. Filling foam: The skin cavity is filled with PUF blocks. The profile of PUFF blocks is grounded to match the inner surface profile of FRP skin and is stuck to the skin with accelerated polyester resin. Closing the bottom skin of the component: The final component is obtained by closing the bottom skin with FRP lamination with a single layer by hand by hand lay-up method. The foam filling can be done by other ways such as pouring ploy and isocyanides liquids in the closed skin by adding agents in the filling mixture. Provide the dimensions assumed and the mould used for manufacturing the bumper by above process, respectively. Figure 3 Operation of sandwich construction 3. ANALYSIS ON BUMPER BY USING ANSYS As mentioned in previous sections, the present design of bumpers has a hollow cross section and with this project an attempt was made to study the design of bumpers and modify the cross section using sandwich construction. A bumper with sandwich construction was designed, modeled and analyzed with supporting numerical calculations to check the improvement in strength of the structure with this design. In the sandwich construction of bumper, core material used is foam and is surrounded by FRP composites laminates. The overall analysis and the main concepts are summarized below editor@iaeme.com

5 C Anil Kumar Reddy In this concept there a foam core of 25-27mm thickness is sandwiched between 1mm thick sheets of FRP composites on to the cold foam in a mould. Adhesive material is used to hold them together as a single unit: Figure 4 sandwich construction The concept has brought in to use for the back rest of rear seats of BMW M3 CSL sports car, by the two young technology firm based in Whilhemsdorf, near Nuremberg, jointly with BASF.This concept has brought for the certain parts of sports car by some firms but this concept has not been used for passenger s cars. Hence this was the attempt made to design, model and analyze a bumper with sandwich construction under static loading constructions. In this project the concept of FEM is implemented along with the supporting software ANSYS. The structure of bumper that we have falls under 3D element. It is a solid structure filled with foam. Hence there are two solids together. Exx = Eyy = (3/8) E11+(5/8) E22 E11and E22 is obtained from the rule of mixtures at 48% volume fraction of fibers with commercial grade polymer resin matrix material. Exx = Eyy = {(3/8) 124G pa }+{(5/8) 6.4G PA)} = (46.5+4) G PA =50.5 G PA Hence the common value of module is taken as an equalling modulus is taken and the two solids are considered as a single solid with the equivalent young s modulus and different loads were applied and the structure was tested under static loading conditions. Flexural Rigidity: E I E=Young s modulus I=Moment of inertia Moment of inertia is more in this case as a solid material is consider in place of a hallow structure. With this increase there is an overall increase in flexural rigidity value which shows that there is an improvement in the strength of structure. To increase this value we could have replaced hallow FRP structure with a solid structure of FRP instead of filling up hallow space by foam. In that case there will be definitely be an increase in the strength but this structure will be quite heavy in weight and there will be wastage of material. Rather, same purpose can be served by filling the hallow space by foam instead of using a solid structure editor@iaeme.com

6 Polymer Composite Sandwich Construction in Automobile to Ensure Safety The Foam is an energy absorbing material and it is capable of absorbing impact energy, as mentioned earlier. More ever, this structure will be much lighter in weight when compared to solid FRP structure Figure 5 cross section of sandwich construction 3.1. CALCULATIONS Present design: Material=HDPE E= young s modulus =32.79 G PA I= moment of inertia = (b1t13/12)- (b2t23/12) = (29 603/12) (27 583/12) = =82998mm4 F= E I = = N-mm2 Our design: Material=composite +foam E= young s modulus = {3/8 124 GPA + 5/8 6.4 GPA} = (46.5+4) GPA = 50.5 GPA I= moment of inertia = bt 3 /12 = ( /12) = mm 4 F= E I =50.5 G PA = E 15 N-mm 2 This shows that the flexural rigidity is improved, almost doubled in the sandwich construction. Now the analysis is extended by testing this design under static loading conditions and the deformation is plotted for various loads over a wide range as follows editor@iaeme.com

7 C Anil Kumar Reddy Figure 6 Meshing view Figure 7 Applying loads 3.2. Comparison of stresses and deformation in HDPE and sandwich construction polymer bumpers at various loads Figure 8 Stress of hallow cross section bumper HDPE at 500N Figure 9 Stress of polymer composite SAND WICH bumper at 500N Figure 10 Deformation of hallow cross section HDPE at 500N editor@iaeme.com

8 Polymer Composite Sandwich Construction in Automobile to Ensure Safety Figure 11 Deformation of polymer composite SAND WICH bumper at 500N Figure 12 Stress of hallow cross section bumper HDPE at 1000N Figure 13 Stress of polymer composite SAND WICH bumper at 1000N Figure 14 Deformation of hallow cross section bumper HDPE at 1000N Figure 15 Deformation of polymer composite SAND WICH bumper at 1000N

9 C Anil Kumar Reddy Figure 16 Stress of hallow cross section bumper HDPE at 1500N Figure.17 Stress of polymer composite SAND WICH bumper at 1500N When the vehicle is hit from front or rear,the parts of the car which first comes in contact with the other vehicle is the front or rear bumper in this case, but it is not the bumper alone which takes u the entire impact load. It absorbs a part of the impact load and the remaining part of the impact load is passed on the parts to which bumper is attached, like chassis of the car, and then the impact is passed to the passenger. The aim is to design the bumper in such a way that its capacity to absorb the impact load is increased by increasing the number of layers so that the major part of the impact is taken up by the bumper itself and the remaining part of the impact which is passed to the other parts of the car and finally to the passengers is decreased by a considerable amount as the major concern is the passenger s safety. Hence after detailed literature survey, the concept of sandwich construction was applied to passengers 4. CONCLUSION To strength the structure of bumpers organic compounds which are used in present design is replaced by FRP composite laminates since composite will act as a stronger material if the fibers are laid in the direction of maximum load. 1. To strengthen the structure further, the concept of sandwich construction was applied. An energy absorbing material (FOAM) of 27mm thickness was sandwiched between 4 FRP composite laminates of 1mm thickness each from all four sides, hence turning the hallow structure to a solid one. 2. By applying Finite Element Method using ANSYS software, a bumper with simplified design and the optimum dimensions with sandwich constructions, was designed, modeled and analyzed and it was found that the bumper with sandwich construction was capable of absorbing more impact load when compared to the present design, will not increase the weight of the structure and cost of manufacturing much at the same time editor@iaeme.com

10 Polymer Composite Sandwich Construction in Automobile to Ensure Safety REFERENCES [1] Shook, Gerald, 1986, Reinforced plastic for commercial composite source Book, ASM, Metals Park, OH. [2] U.S Department of Agriculture Forest Services, 1987,Wood Handbook: Wood as an Engineering Material, Agricultural Handbook NO 72,DC. [3] Introduction to Composites, 4thedition, Composite Institute, society of plastics Industry, New York, NY, [4] Rosato, Dominic V, Designing with Reinforced Plastics, Hanser/Gardner, Cincinnati, Ohio, [5] Handbook of Poly ethylene by Andrew j.peacock. [6] FIBRE REINFORCED POLYMER COMPOSITE APPLICATION IN USA Published in the First Korea /U.S.A road Workshop Proceedings, January 28-29, [7] News Realizes- FOAMS for light weight construction presented by DR.HERBERT BORGER, CEO, AC.S ADVANCE COMPOSITE SYSTEMS, GmbH, Wilhelmsdorf