-
it
a, A43400 Ulogy
Available online 12 June 2011
Keywords:A. CompositeE. MechanicalH. Selection of components
e co
matrices can improve mechanical properties of natural bre
composite. Moreover, geometric optimiza-
absorption, material consumption and cost [5]. The previous
stud-ies did not completely full the impact strength requirement of
thebumper 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].
ers have done many investigations to expand the application
pos-sibilities of natural bres in automotive industry such as front
doorlinens, rear door linens, boot linens, parcel shelves, seat
backs, sun-roof sliders, headliners, door-trim panel and trunk
liner [1214]. Infact, the majority of their products are used in
aesthetic and semistructural components. Mussig [15] utilized hemp
and PTP bresin 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-ers studied on energy absorption of wood for automotive
structural
Corresponding author. Tel.: +60 16 65 65 296; fax: +60 3 8656
7122.E-mail addresses: [email protected], [email protected]
(M.M.
Materials and Design 32 (2011) 48574865
Contents lists availab
Materials an
elsDavoodi).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-sorber and bumper beam [1] (see Fig. 1). Bumper beam is the
majordamping structure component in passenger cars. Besides, two
en-ergy absorbers damp both the low and high impact energy by
elas-tic deection between two traverse-xing points and
crushingprocess respectively [2,3]. Due to safety requirements, in
develop-ing the bumper beam, the careful design, optimized
structure, highquality and consistent manufacturing must be
considered [4]. Inaddition, bumper beam selection can improve
structural energy
tual design of the automotive bumper system and used theweighted
objective method to nd 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-1. Introduction0261-3069/$ - see
front matter 2011 Elsevier Ltd.
Adoi:10.1016/j.matdes.2011.06.011tions have a signicant role in
structural strength improvement. This study focused on selecting
the bestgeometrical bumper beam concept to fulll the safety
parameters of the dened product design speci-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-speed impact
test was simulated under the same conditions in Abaqus V16R9
software. Six weightedcriteria, which were deection, strain energy,
mass, cost, easy manufacturing, and the rib possibility
wereanalyzed to form an evaluation matrix. Topsis method was
employed to select the best concept. It is con-cluded that double
hat prole (DHP) with dened material model can be used for bumper
beam of a smallcar. In addition, selected concept can be
strengthened by adding reinforced ribs or increasing the thick-ness
of the bumper beam to comply with the dened PDS.
2011 Elsevier Ltd. All rights reserved.
Conceptual design is the rst stage of product development
tosatisfy customer requirements. Sapuan et al. [1] studied on
concep-Received 10 March 2011Accepted 7 June 2011
technical and economic advantages. However, their low mechanical
properties have limited their partic-ular application in automotive
structural components. Hybridizations with other reinforcements
orConcept selection of car bumper beam wbio-composite material
M.M. Davoodi a,, S.M. Sapuan a, D. Ahmad b, A. AidyaDepartment
of Mechanical and Manufacturing Engineering, Universiti Putra
Malaysia,bDepartment of Biological and Agricultural Engineering,
Universiti Putra Malaysia, 4340cDepartment of Applied Physics and
Mechanical Engineering, Lule University of Techno
a r t i c l e i n f o
Article history:
a b s t r a c t
Application of natural br
journal homepage: www.ll rights reserved.h developed hybrid
. Khalina b, Mehdi Jonoobi c
0 UPM Serdang, Selangor, MalaysiaPM Serdang, Selangor, Malaysia,
Sweden
mposites is going to increase in different areas caused by
environmental,
le at ScienceDirect
d Design
evier .com/locate /matdes
-
components [16], few studies have been conducted on
applicationof natural bre in structural automotive components.
This research focused on analyzing, evaluating and selecting
theoptimum concept among eight different bumper beam concepts,and
particularly concentrated on safety purposes of a bumperbeam PDS.
Based on the National Highway Trafc Safety Adminis-tration (NHTSA),
car bumper low impact test was simulated by -nite element software,
Abaqus Ver16R9, to address the highestenergy absorption and maximum
possible deection. 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-pointed for selecting the best concept of the bumper
beam througheight systematic evaluation processes. It was concluded
that Dou-ble Hat Prole (DHP) as a best concept. Moreover, this
study dem-onstrated the feasibility of the nite element analysis in
selectingthe best structural concepts to overcome the weak inherent
prop-erties of natural bre, 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-ceptual design, which is derived from customer requirement
voiceof the customer [17,18] to nd 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
[2125].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 Pughs method [23] or quality function deployment(QFD) [26].
Fuzzy ANP-based, evaluate a set of conceptual designalternatives to
satisfy both customer satisfaction and engineeringspecications
[27]. Analytical Hierarchy Process (AHP) is a mathe-matically based
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 conicting
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 is
Fig. 1. Bumper system components.
4858 M.M. Davoodi et al. /Materials and Design 32 (2011)
48574865Fig. 2. Selected parametersbased 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 tocarry out the analysis for better
options [30]. This method has beenappointed to select the best
concept in this research.for bumper beam PDS.
-
2.2. Product design specication (PDS)
To perform the customer requirements and expectation to a
de-tailed technical document called PDS [31]. It is quite difcult
to n-ish the exact PDS in the early stage of product development,
whilethe knowledge of design requirements is imprecise and
incomplete[32]. PDS originates by disorganized brainstorming team
with var-ious prociency, 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 specication in this study.
Bumper beam PDS consisted of safety, performance, weight,size,
cost, environment issue, appearance (see Fig. 2). Whole
PDSparameters can be classied into three main subdivisions such
asmaterial, manufacturing and design. Since energy absorption
ofdifferent concept is the core competency of this study, 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-sengers car, issued by safety organization, insurance
companiesor original equipment manufacturer (OEM) [33]. Insurance
compa-nies usually offer more severe conditions in order to
decrease theirown costs. This study follows safety criteria of the
European carmanufacturer.
(1) Low impact test: Longitudinal pendulum impact test by4.0
km/h (2.5 mph), and corner pendulum impact test by2.4 km/h (1.5
mph) with any bumper visual, functional,and safety damages.
(2) High speed test: No bumper damage or yielding after 8 km/h(5
mph) frontal impact into a at, rigid barrier.
(3) Pedestrian impact test: In this test, a leg-form impactor
ispropelled toward a stationary vehicle at a velocity of 40 km/h
(25 mph) parallel to the vehicles longitudinal axis. The testcan 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
< 150 g and the shear d < 6 mm andbending a < 15
M.M. Davoodi et al. /Materials and Design 32 (2011) 48574865
4859Fig. 3. Bumper beam conceptual selection owchart.
-
[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 xing 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 xing
points during energy dampingprocess. When the impact load applied
to the bumper, thebeam initial curvature intends to remove. So,
some designer
4860 M.M. Davoodi et al. /Materials and Design 32 (2011)
48574865Since material development and its manufacturing method
arediscussed in the previous study, this research emphasizes on
design
Fig. 4. Overall dimensions of different concepts.parameters 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 dened goal of the product
should be attainable [23]. Installa-tion: Design for manufacturing
and assembly (DFMA) help to min-imize the bumper components in
product or assembly tomake easyassembling with optimize xing 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 beam acts as a plain simply supported beam. It usuallyxes
to the frontal chassis sides to absorb collision energy. Thereare
ve bumper system assembling methods for energy absorption
Table 1Finite element preliminary output data.
No. Properties Weight RCP COP CCP
Reverse Cprole
Closed obliqueprole
Curved Cprole
1 Material cost 0.15 24.40 29.00 18.602 Easy
manufacturing0.1 2 1 4
3 Product weight 0.2 2.44 2.9 1.864 Strain energy 0.3 2482.82
43419.92 38825.145 Add rib
possibility0.1 2 1 5
6 Min deection 0.15 16.92 29.86 21.34mounted a bar to link
between beams xing 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
contactarea in xing points increase the stress concentration,
whichshould be modied in design stage [40].
(3) Fixing method: Bumper beam has the main role in caring
theweight of the bumper system. Proper xing method couldkeep the
bumper system more stable and reliable duringthe energy absorption.
Designer usually considers a C-chan-nel prole in frontal chassis to
hold the bumper beam orabsorbers in order to increase the xing
contact area anddecrease the stress. Additional xing point keeps
the bum-per system more consistent, but extends the assembly
time.The lateral xing points considered slide shape to let the
fas-cia move safely in the desired gap to prevent the bumperside
breaking.
(4) Strengthen rib: Strengthen rib increase distortion
resistance,rigidity and structural stiffness by less material in
slenderwalls [41] and provide the required impact severity
[42].Pattern, thickness, tip and end llet of the ribs should
bedesigned according to load direction, impact position, mate-rial
and manufacturing process. Since the material thickness,increase at
the ribs 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
DHP DCC DCP SHP SCP
Double hatprole
Double Cclosed
Double Cprole
Simple hatprole
Simple Cprole
25.50 29.40 25.60 21.90 22.503 2 4 3 5
2.55 2.94 2.56 2.19 2.2576106.53 63671.64 44910.27 47231.52
2137.625 4 5 4 518.34 25.72 21.15 22.92 16.73
-
developed 3D model were imported to Abaqus Ver16R9 for
niteelement analysis (see Fig. 4).
3.2. Low-speed impact simulation, boundary condition and
meshing
There are three low-speed impact regulations to check thebumper
performance. ECE Regulation No 42 [48], National High-way Trafc
Safety Administration (NHTSA) - Code 49 Part 58[49], and Canadian
Motor Vehicle Safety Regulation (CMVSR)[50]. Canadian safety
regulation has the same limitation and safetydamage as NHTSA
(pendulum test 4 km/h of bumper face and2.5 km/h bumper corner),
but the speed is double. In this simula-tion method, pendulum with
the same car weight tilted in speci-ed angle to make the linear
speed 4 km/h at the contactposition. After the test, the lights
must work, bonnet, boot, doorsoperate in the normal manner, and all
the essential features forsafe operation of the vehicle must still
be serviceable.
The block impactor is modeled according to the standard.
Thedensity of the pendulum is modied to satisfy cars weight
impactforce, which is between 700 and 950 kg for small city car.
The blockis pivoted about its top left corner and rotates with
1.6859 rad/s tomake 4 km/h linear speed at contact position. Whole
bumper beamconcepts are located at the dened height according to
the stan-dard. Both traverse xing points were joined by spring-
dampermechanism to their positions in order to tolerate the damping
loaduntil car weight. If the load exceeds upon the car weight the
bum-
and Design 32 (2011) 48574865 4861by 7% and decrease elongation
by 19% [9,11,43]. The opti-mized reinforced ribs presented higher
energy absorptionperformance compared with the empty and
foam-lledbeams [44].
(5) Material properties: Material behavior, rigidity and
ductility,has a great inuence in energy absorption. High
rigidityincreases the car protecting capability, but decreases
damp-ing capacity and causes impact load transmission to
thecompartment. In low impact test, bending strength not letthe
beam to go through the plastic region, so the materialshould
withstand the impact load and keep their dimen-sional stability to
stay intact.
(6) Cross-section: Optimizing cross-section of a bumper
beammagnies the strength, dimensional stability and
dampingcapability [36]. It has signicant effects in the energy
damp-ing rate and bending resistance compare with other param-eters
[45,46]. In this research, eight different cross-sectionswere
investigated to select the optimum concepts in energyabsorption and
deection during the low impact test, alongwith material weight,
easy manufacturing, supplement ribpossibility and material
cost.
(7) Manufacturing method: Manufacturing method should benalized
in design stage. The applied pressure performs bet-ter adhesion
between bre and matrix and makes the prod-uct more stable, stiffer,
but heavier. Parting line, draft angle,bre direction, product
warpage, cooling time, materialshrinkage, and post shrinkage are
some effective parametersin selecting manufacturing method.
Besides, production rateand material characteristic has a signicant
effect in manu-facturing method selection.
(8) Thickness: Increasing the bumper beam thickness improvesthe
strength and energy absorption, but it greatly increasesthe weight.
However, additional thickness increases thestructural stability; it
has some manufacturing limitation,especially in thermoplastic
products. The ratio of strengthand weight improve by assigning the
optimized thicknessand providing more effective energy absorption
[47].
In this study, energy absorption improvement is originated
bycross-section, material and manufacturing optimizations,
whichhave less effect in weight enhancement, then other
parameterssuch as strengthened ribs, and thickness, will be
employed.
3. Materials and methods
In the previous studies, the hybrid composite material
wasdeveloped and thermoplastic toughening was employed to im-prove
the impact property, but it still less than common bumperbeam
material GMT. Therefore, geometrical improvement wasused to comply
with the dened PDS. This study focused on con-cept selection among
eight-bumper beam prole based on six dif-ferent weighted criteria.
The process of concept selectionillustrated as follows (see Fig.
3). First, whole concepts modeledand imported to the nite element
analysis software, then thelow impact test was accomplished, and
along with the result ofother criteria, the selection matrix was
performed, and Topsismethod was employed to select the best
concept.
3.1. Geometrical 3D model development
The idea of the geometrical 3D model came up with bench-marking
different brand of passengers car, patents, industrial de-sign
practice and car manufacturer products. Whole 3D concepts
M.M. Davoodi et al. /Materialswere designed in Catia V5R17
software symmetrically as similaras the real bumper beam with the
same overall dimensions, i.e.height, breadth, thickness, radius and
material model. Next, entireper together with car moves along the
impact direction. Table 1shows the cross-section area, volume,
number of nodes and ele-ments in each cross-section.
3.3. Topsis conceptual selection method
Six criterias are nominated for eight alternative concepts
andspecialist appointed the weighted values are appointed for
everycriterion. Topsis is an effective method for multi-criteria
deci-sion-making (MCDM). Hwang and Yoon introduced the Topsis
Fig. 5. Strain energy in different cross sections in Abaqus.Fig.
6. The displacement graph of whole concepts.
-
method based on the idea that the best alternative should have
theshortest distance from an ideal solution [51]. The algorithm
con-siders ideal and non-ideal solution and help decision maker
toevaluate ranking and select the best one. Topsis has been well
uti-lized in project selection [52], material selection [53] and
otherareas. The procedure of Topsis expressed in following
steps:
D
C1 C2 CnA1 x11 x12 x1nA2 x21 x22 x2n... ..
. ... ..
. ...
Am xm1 xm2 xmn
1
W w1;w2; . . . ;wn;where A1, A2, . . ., Am are potential
alternatives that decision makersneed to select and C1, C2, . . .,
Cn are criterion, which evaluate thealternative performance are
calculated, xij is the rating of alternativeAi with respect to
criterion Cj when wj is the weight of criterion Cj[54]
(1) Determine the normalized decision matrix.
(2)
(3)
(4) Determine the separation measures, using the n-dimen-sional
Euclidean distance. The separation of each alternativefrom the
ideal solution is given as:
di Xnj1
v ij vj 2( )1=2
; i 1;2; . . . ;m 5
Similarly, the separation from the negative ideal solution
isgiven as:
di Xnj1
v ij vj 2( )1=2
; i 1;2; . . . ;m 6
(5) Determine the relative closeness to the ideal solution.
Therelative closeness of the alternative Ai with respect to A+
isdened as:
cli di
di di ;0 6 cli 6 1; i 1;2; . . . ;m 7
(6) Rank the preference order. For ranking alternatives
usingthis index and rank alternatives in decreasing order.
Product w0.2
2
2
1.86
2.55
2.94
2.56
2
4862 M.M. Davoodi et al. /Materials and Design 32 (2011)
48574865ated with the cost criterion.
Table 2Evaluation matrix for selecting the best prole
concept.
No. Concepts Name Material cost Easy manufacturing0.15 0.1
1 RCP 24.40 2
2 COP 29.00 1
3 CCP 18.60 4
4 DHP 25.50 3
5 DCC 29.40 2
6 DCP 25.60 4
7 SHP 21.90 38A minj
v ijji 2 I maxj
v ijji 2 J ji 1;2; . . . ;m
where I is associated with a benet criterion, and J is associ-A
maxj
v ijji 2 I minj
v ijji 2 J ji 1;2; . . . ;n
4Vm1; . . . Vmj; . . . Vmn
where wj is the weight of the ith attribute or criterion,
andPnj1wj 1:
Calculate the positive ideal and negative ideal solution:
V ND:Wnn V1i; . . . V1j; . . . V1n
..
. ... ..
.
3nij xijPmj1x
2ij
q ; i 1; . . . ;m; j 1; . . . ; 2Calculate the weighted
normalized decision matrix.
SCP 22.50 5 2.19 47231.5 4 22.92.2576106.5 5 18.34
63671.6 4 25.72
44910.3 5 21.1538825.1 5 21.34.44 2482.82 2 16.92
.9 43419.9 1 29.86eight Strain energy Rib possibility Minimum
deection0.3 0.1 0.154.1. Impact energy
Low-speed impact test is tested for whole bumper concepts
inorder to nd the strain energy (see Fig. 5). The graph shows
thatthe concept named double hat prole (DHP) has presented
thehighest strain energy.
The longitudinal displacements (X direction) are demonstratedin
Fig. 6. It shows the concepts single C prole (SCP) and closed
ob-lique prole (COP) have displayed minimum and maximum deec-tion
in low impact test respectively.4. Results
The safety parameters along with other PDS criteria are
consid-ered as parameters in selecting the bumper beam concepts.
Theabsorbed energy and deection are derived from simulated
lowimpact test, and other criteria were assessed by scoring by the
ex-pert to the converted qualied value to the quantify value
andother calculation. The output information made a decision
matrixfor selecting the best result by Topsis method to comply with
thePDS requirement.2137.62 5 16.73
-
Table 5Weighted normalized decision matrix.
Material cost Easy manufacturing Product weight Strain energy
Rib possibility Maximum deectionMC EM PW SE RP MD
0.05208 0.02182 0.06944 0.00563 0.01709 0.040730.06190 0.01091
0.08254 0.09847 0.00854 0.071870.03970 0.04364 0.05294 0.08805
0.04272 0.051360.05443 0.03273 0.07258 0.17261 0.04272
0.044140.06275 0.02182 0.08367 0.14440 0.03417 0.061910.05464
0.04364 0.07286 0.10185 0.04272 0.050910.04675 0.03273 0.06233
0.10712 0.03417 0.055170.04803 0.05455 0.06404 0.00485 0.04272
0.04027
Table 6The positive and negative ideal solution matrix.
Material cost Easy manufacturing Product weight Strain energy
Rib possibility Maximum deection
MC EM PW SE RP MD0.039703 0.054554 0.05294 0.172606 0.042718
0.040270.062756 0.010911 0.08367 0.004848 0.008544 0.07184
Table 7Separation of each alternative from the ideal
solution.
RCP COP CCP DHP DCC DCP SHP SCP
0.173306 0.104575 0.085973 0.033072 0.062324 0.076539 0.072094
0.1683310.038462 0.093637 0.105163 0.175352 0.142658 0.110778
0.112176 0.068367
Table 8The relative closeness to the ideal solution.
RCP COP CCP DHP DCC DCP SHP SCP
0.181614 0.472414 0.550201 0.841321 0.695954 0.591394 0.608758
0.288836
Table 3Decision matrix for selecting the concepts of bumber
beam.
Subjective weight 0.15 0.1 0.2 0.30.1 0.15 0.15
No. Name Material cost MC Easy manufacturing EM Product weight
PW Strain energy SE Rib possibility RP Maximum deection MD
1 RCP 24.4 2 2.44 2462.82 2 16.922 COP 29.0 1 2.90 43419.93 1
29.863 CCP 18.6 4 1.86 38825.14 5 21.344 DHP 25.5 3 2.55 76106.53 5
18.345 DCC 29.4 2 2.94 63671.64 4 25.726 DCP 25.6 4 2.56 44910.27 5
21.157 SHP 21.9 3 2.19 47231.52 4 22.928 SCP 22.5 5 2.25 21371.62 5
16.73
Table 4Normalized matrix.
Material Cost MC Manufacturing EM Product weight SE Strain
energy Rib possibility RP Maximum deection MD
0.412682 0.109109 0.41268 0.328248 0.085436 0.479140.264686
0.436436 0.26469 0.293512 0.427179 0.342430.362876 0.327327 0.36288
0.575353 0.427179 0.294290.418374 0.218218 0.41837 0.481347
0.341743 0.412710.364299 0.436436 0.36435 0.339515 0.427179
0.339380.311646 0.327327 0.31165 0.357063 0.341743 0.367780.320185
0.545545 0.32018 0.016162 0.427179 0.26846
M.M. Davoodi et al. /Materials and Design 32 (2011) 48574865
4863
-
Table 2 shows eight different concepts along with six
weightedcriteria. There are two qualitative criteria, easy
manufacturing andrib possibility, which have changed to the
quantitative in range oneto ve. One in the lowest and ve in the
highest possibility as-signed to different concepts. Strain energy
and minimum deec-tion have been derived from FEA results. Material
estimated costcalculated based on the ingredient and material
consumptionscost. Material weight was calculated according to the
density ofthe material, which has been found in advance.
4.2. Selecting the best concept by Topsis method
There are three elimination phases to narrow down the
possibledesign concepts to the nal concept, named initial screening
phase,decision matrix phase and evaluation phase. Decision matrix
basedon initial screening was made by eight concepts and six
criterion.Material cost, product weight and maximum deection
havenegative value, which should consider as a negative value
andthe following present the evaluation phase (see Table 3),
whereA1, A2, . . ., Am (Rows) are possible alternatives among which
deci-sion makers have to choose and C1, C2, . . ., Cn (column) are
criteriawith which alternative performance are measured, xij is the
rating
strengthening ribs, and thickness. He found that the SMC can be
re-
4864 M.M. Davoodi et al. /Materials andplaced by GMT material,
while the strengthen rib removed andthickness decreased to 2.5 mm
in order to increase 5% deectionto cover enough room after the
impact as well as easy productionof alternative Ai with respect to
criterion Cj while wj is the weightof criterion Cj. The matrix
normalized between 01 to make itdimensionless by formula (see
Tables 48).
5. Discussion
According to the automotive safety standards, all passengerscars
have to overcome the frontal and rear low-speed impact testwithout
any serious damage [9,11,55]. The severity of the barrierimpact
load should not deform the bumper far more beyond theplastic region
to fail the related parts function. Hosseinzadehet al. [9] compared
impact property of the GMT and SMC bumperbeam by changing different
parameters, i.e. material, shape,Fig. 7. Displacement prole of
double hat prole after impact.6. Conclusions
Impact property of developed toughened hybrid
bio-compositematerial did not completely fulll the common bumper
beammaterial GMT. Therefore, in this study the geometric concept
selec-tion is investigated to enhance structural energy absorption
anddeection besides other criteria in the car bumper beam
develop-ment. Eight bumper beam concepts with the same material
modelunder low impact test standard conditions are simulated. It is
con-cluded that proper concept selection has an important role
instructural strength, while material is considered as a constant
fac-tor. Moreover, it is resulted that bio-based composite material
hasa potential to be used in automotive structural components
bystructural optimization. The nominated concept (DHP) veried
ascompared with some available car bumper beams prole. It
pre-sented that the epoxy toughened hybrid kenaf/glass bre
compos-ite can be employed in the small-sized car bumper
beam.Although, adding strengthened ribs can enhance its
performance,it may decrease the required room after impact.
Moreover, authorbelieves that the real low impact test should be
done to verify thestability of developed hybrid bio-composite
material under theproposed concept.
Acknowledgements
The authors wish to thank Universiti Putra Malaysia for
thenancial support to carry out this research through
ResearchUniversity Fellowship Scheme to the principal author.
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Concept selection of car bumper beam with developed hybrid
bio-composite material1 Introduction2 Basic design procedure2.1
Conceptual design of bumper beam2.2 Product design specification
(PDS)2.3 Effective parameters in bumper beam energy absorption
3 Materials and methods3.1 Geometrical 3D model development3.2
Low-speed impact simulation, boundary condition and meshing3.3
Topsis conceptual selection method
4 Results4.1 Impact energy4.2 Selecting the best concept by
Topsis method
5 Discussion6 ConclusionsAcknowledgementsReferences