Concept Selection of Car Bumper Beam With Developed Hybrid Bio-composite Material

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Concept Selection of Car Bumper Beam With Developed Hybrid Bio-composite Material
  Concept selection of car bumper beam with developed hybridbio-composite material M.M. Davoodi a, ⇑ , S.M. Sapuan a , D. Ahmad b , A. Aidy a , A. Khalina b , Mehdi Jonoobi c a Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia b Department of Biological and Agricultural Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia c Department of Applied Physics and Mechanical Engineering, Luleå University of Technology, Sweden a r t i c l e i n f o  Article history: Received 10 March 2011Accepted 7 June 2011Available online 12 June 2011 Keywords: A. CompositeE. MechanicalH. Selection of components a b s t r a c t Application of natural fibre composites is going to increase in different areas caused by environmental,technical and economic advantages. However, their low mechanical properties have limited their partic-ular application in automotive structural components. Hybridizations with other reinforcements ormatrices can improve mechanical properties of natural fibre composite. Moreover, geometric optimiza-tions have a significant role in structural strength improvement. This study focused on selecting the bestgeometrical bumper beam concept to fulfill the safety parameters of the defined product design specifi-cation (PDS). The mechanical properties of developed hybrid composite material were considered in dif-ferent bumper beam concepts with the same frontal curvature, thickness, and overall dimensions. Thelow-speedimpacttestwassimulatedunderthesameconditionsinAbaqusV16R9software. Sixweightedcriteria,whichweredeflection,strainenergy,mass, cost,easymanufacturing, andtheribpossibilitywereanalyzedto formanevaluation matrix. Topsis method was employed to select thebest concept. It is con-cludedthatdoublehatprofile(DHP)withdefinedmaterialmodelcanbeusedforbumperbeamofasmallcar. In addition, selected concept can be strengthened by adding reinforced ribs or increasing the thick-ness of the bumper beam to comply with the defined PDS.   2011 Elsevier Ltd. All rights reserved. 1. Introduction Concept optimizations of the car bumper beam can improvestructural energy absorption to meet the PDS requirements. Bum-per system is composed of three main elements fascia, energy ab-sorberandbumperbeam[1](seeFig.1).Bumperbeamisthemajor damping structure component in passenger cars. Besides, two en-ergyabsorbersdampboththelowandhighimpactenergybyelas-tic deflection between two traverse-fixing points and crushingprocess respectively [2,3]. Due to safety requirements, in develop-ingthebumperbeam, thecarefuldesign, optimizedstructure, highquality and consistent manufacturing must be considered [4]. Inaddition, bumper beam selection can improve structural energyabsorption, material consumption and cost [5]. The previous stud-iesdidnotcompletelyfulfiltheimpactstrengthrequirementofthebumper PDS even in case where polybutylene terephthalate (PBT)was supplemented to the hybrid bio-composite material [6,7].Therefore, in this recent study the optimized concept selection isemployed to improve the impact stability of structure [8].Conceptual design is the first stage of product development tosatisfycustomerrequirements.Sapuanetal.[1]studiedonconcep-tual design of the automotive bumper system and used theweighted objective method to find the best concept. Hosseinzadehet al. [9] conducted a research to substitute the high strength SMCwith common bumper beam material GMT to improve energyabsorption. Furthermore, Davoodi et al. [10] studied about com-posite elliptical energy absorber for pedestrian impact test withsystematic exploitation of proven ideas. Marzbanrad et al. [11]studied about the material, thickness, shape and impact conditionof the bumper beam to improve the crashworthiness and low-velocity impact. He offered to substitute SMC with GMT materialto absorb more structural impact. Also, European car manufactur-ers have done many investigations to expand the application pos-sibilitiesofnaturalfibresinautomotiveindustrysuchasfrontdoorlinens,reardoorlinens, bootlinens, parcelshelves,seatbacks,sun-roofsliders, headliners,door-trimpanel andtrunkliner [12–14]. Infact, the majority of their products are used in aesthetic and semistructural components. Mussig [15] utilized hemp and PTP  fibresin a body of bus as reinforcements, a vegetable-based thermosetresin as matrix, and sheet molding compound (SMC) as fabricatingmethod for structural components. Although, the earlier research-ersstudiedonenergyabsorptionofwoodforautomotivestructural 0261-3069/$ - see front matter   2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.matdes.2011.06.011 ⇑ Corresponding author. Tel.: +60 16 65 65 296; fax: +60 3 8656 7122. E-mail addresses:, (M.M.Davoodi).Materials and Design 32 (2011) 4857–4865 Contents lists available at ScienceDirect Materials and Design journal homepage:  components [16], few studies have been conducted on application of natural fibre in structural automotive components.Thisresearchfocusedonanalyzing,evaluatingandselectingtheoptimum concept among eight different bumper beam concepts,and particularly concentrated on safety purposes of a bumperbeam PDS. Based on the National Highway Traffic Safety Adminis-tration (NHTSA), car bumper low impact test was simulated by fi-nite element software, Abaqus Ver16R9, to address the highestenergy absorption and maximum possible deflection. The samematerial properties and constant overall dimensions were consid-ered for whole concepts. Finally, decision matrix came up witheight alternatives against six criteria. Topsis method was ap-pointedforselectingthebestconceptofthebumperbeamthrougheight systematic evaluation processes. It was concluded that Dou-ble Hat Profile (DHP) as a best concept. Moreover, this study dem-onstrated the feasibility of the finite element analysis in selectingthe best structural concepts to overcome the weak inherent prop-erties of natural fibre, and to get better mechanical performancefor automotive structural application. 2. Basic design procedure  2.1. Conceptual design of bumper beam The preliminary stage of product development start with con-ceptualdesign,whichisderivedfromcustomerrequirement‘‘voiceof the customer’’ [17,18] to find a solution to satisfy the functionaldesign problems [19]. Imprecise engineering calculation, designand material selection, might increase up to 70% the total productcost for redesigning [20]. Designer has to select the most suitableidea from different possible solutions or combination of materialselection and component design to meet the desired PDS in eachdesign stage to decrease the rework expense [21–25].Therefore,many tools are developed to evaluate design concept selection(DCS) and compromise different effective factors, i.e. customerrequirements, designer intentions and market desire.Decision matrix-based methods, offer the qualitative compari-son such as Pugh’s method [23] or quality function deployment(QFD) [26]. Fuzzy ANP-based, evaluate a set of conceptual designalternatives to satisfy both customer satisfaction and engineeringspecifications [27]. Analytical Hierarchy Process (AHP) is a mathe-maticallybased technique for analyzing complex situations, whichwere sophisticated in its simplicity [28]. Multi criteria decision-making (MCDM) is an effective method for single selection amongmixed criteria. Multi-attribute decision-making technique(MADM) is a conflicting preferences’ solution among criteria forsingle decision makers’. Topsis is well suited technique to dealingwith multi attribute or multi-criteria decision-making (MADM/MCDM) problems in real world ideal solutions [29]. Its method isbased on ‘‘chosen alternative has shortest distance from positiveideal solution and farthest distance from negative ideal solution’’.It helps to organize problems, compare, and rank alternatives tocarryouttheanalysisforbetteroptions[30]. Thismethodhasbeenappointed to select the best concept in this research. Fig. 1.  Bumper system components. Fig. 2.  Selected parameters for bumper beam PDS.4858  M.M. Davoodi et al./Materials and Design 32 (2011) 4857–4865   2.2. Product design specification (PDS) Toperformthecustomerrequirements andexpectationtoade-tailedtechnicaldocumentcalledPDS[31].Itisquitedifficulttofin-ish the exact PDS in the early stage of product development, whiletheknowledgeofdesignrequirementsisimpreciseandincomplete[32]. PDS srcinates by disorganized brainstorming teamwith var-ious proficiency, i.e. manufacturing, designing, selling, assembling,maintaining, and might be improved due to new product changesand manufacturing limitations. Safety was the main goal amongdifferent bumper PDS specification in this study.Bumper beam PDS consisted of safety, performance, weight,size, cost, environment issue, appearance (see Fig. 2). Whole PDSparameters can be classified into three main subdivisions such asmaterial, manufacturing and design. Since energy absorption of different concept is the corecompetencyof thisstudy, it is empha-sized in the PDS safety parameters. Some of the mechanical andphysical properties’ values are received from experimental resultsand others from existing PDS data.Safety: There are different bumper safety regulations for pas-senger’s car, issued by safety organization, insurance companiesor original equipmentmanufacturer(OEM) [33]. Insurancecompa-niesusuallyoffer moresevere conditionsin order to decreasetheirown costs. This study follows safety criteria of the European carmanufacturer.(1) Low impact test: Longitudinal pendulum impact test by4.0km/h (2.5mph), and corner pendulum impact test by2.4km/h (1.5mph) with any bumper visual, functional,and safety damages.(2) Highspeedtest:Nobumperdamageoryieldingafter8km/h(5mph) frontal impact into a flat, rigid barrier.(3) Pedestrian impact test: In this test, a ‘‘leg-form’’ impactor ispropelled toward a stationary vehicle at a velocity of 40km/h(25mph)paralleltothevehicleslongitudinalaxis. Thetestcan be performed at any location across the face of the vehi-cle, between the 30   bumper corners. So the impact criteriafor 2010 should be  a  <150g and the shear  d  <6mm andbending  a  <15  Fig. 3.  Bumper beam conceptual selection flowchart. M.M. Davoodi et al./Materials and Design 32 (2011) 4857–4865  4859  Since material development and its manufacturing method arediscussedinthepreviousstudy,thisresearchemphasizesondesignparameters in PDS.  Size : Dimension of the bumper beam dependson energy absorption value, which related to car size and weight. Maintenance : Design for assembly (DFA) and design for manufac-turing (DFM) should consider during product design.  Performance :The defined goal of the product should be attainable [23].  Installa-tion : Design for manufacturing and assembly (DFMA) help to min-imizethebumpercomponentsinproductorassemblytomakeeasyassembling with optimize fixing point [34]. Material should be se-lect according to the required properties or desired problem solu-tion [35]. Materials of the bumper should be light, costcompetitive, accessible, producible, recyclable, and biodegradable.  2.3. Effective parameters in bumper beam energy absorption Bumper beamacts as a plain simply supported beam. It usuallyfixes to the frontal chassis sides to absorb collision energy. Therearefivebumpersystemassemblingmethodsfor energyabsorption[10]. In this study, bumper beam was placed after fascia and wasmounted to the main chassis through energy absorbers. Besides,are different effective parameters to improve the energy absorbingperformance in a bumper beam as follows.(1) Frontal curvature: Frontal curvature increases the roombetween fixing points and top extremity beam curvature. Itstrengthens the beam stability, and extends the requiredcollision displacement. Besides, the aesthetic purposes, thecurve facilitates better load impact distribution throughthe frontal beam and fixing points during energy dampingprocess. When the impact load applied to the bumper, thebeam initial curvature intends to remove. So, some designermounted a bar to link between beam’s fixing points in orderto strengthen the outward motion and energy absorptiontendency [36,37]. Bumper beam is an offset of front bumperfascia to provide a consistent level of protection across thevehicle [38].(2) Stress concentration: Stress concentration decreases fatiguelife, durability, and energy absorption of the bumper beamin instance loading. Numerical shape optimizations methodcould be employed to decrease stress concentration [39],which is not emphasized in this study. Manufacturing limi-tation cause to cut out some of the beam surface in orderto install the sensors, fog lamps, or make a hole to mountthe beam into the front-end, which makes some tiny crackinto the cutting area, increase the stress concentration anddecrease the performance. Sharp corners and less contactareainfixingpointsincreasethestressconcentration, whichshould be modified in design stage [40].(3) Fixingmethod:Bumperbeamhasthemainroleincaringtheweight of the bumper system. Proper fixing method couldkeep the bumper system more stable and reliable duringthe energy absorption. Designer usually considers a C-chan-nel profile in frontal chassis to hold the bumper beam orabsorbers in order to increase the fixing contact area anddecrease the stress. Additional fixing point keeps the bum-per system more consistent, but extends the assembly time.Thelateralfixingpointsconsideredslideshapetoletthefas-cia move safely in the desired gap to prevent the bumperside breaking.(4) Strengthenrib: Strengthenribincreasedistortionresistance,rigidity and structural stiffness by less material in slenderwalls [41] and provide the required impact severity [42]. Pattern, thickness, tip and end fillet of the ribs should bedesigned according to load direction, impact position, mate-rialandmanufacturingprocess.Sincethematerialthickness,increase at the rib’s contact area, it causes sink marks; how-ever, this is not important for the bumper beam as non-aesthetic part. Strengthen ribs increase the impact energy Fig. 4.  Overall dimensions of different concepts.  Table 1 Finite element preliminary output data. No. Properties Weight RCP COP CCP DHP DCC DCP SHP SCPReverse CprofileClosed obliqueprofileCurved CprofileDouble hatprofileDouble CclosedDouble CprofileSimple hatprofileSimple Cprofile1 Material cost 0.15 24.40 29.00 18.60 25.50 29.40 25.60 21.90 22.502 Easymanufacturing0.1 2 1 4 3 2 4 3 53 Product weight 0.2 2.44 2.9 1.86 2.55 2.94 2.56 2.19 2.254 Strain energy 0.3 2482.82 43419.92 38825.14 76106.53 63671.64 44910.27 47231.52 2137.625 Add ribpossibility0.1 2 1 5 5 4 5 4 56 Min deflection 0.15 16.92 29.86 21.34 18.34 25.72 21.15 22.92 16.734860  M.M. Davoodi et al./Materials and Design 32 (2011) 4857–4865
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