Fabrication of Woven Honeycomb Structures for Advanced Composites

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Fabrication of Woven Honeycomb Structures for Advanced Composites
BAŞAL BAYRAKTAR G et al. Fabrication of Woven Honeycomb Structures... TEXT LEATH REV 1 (3-4) 2018 114-119.

Fabrication of Woven Honeycomb Structures for Advanced
Composites
Güldemet BAŞAL BAYRAKTAR*, Ata KIANOOSH, Derya BILEN
Ege University, Department of Textile Engineering, İzmir 35100, Turkey
*guldemet.basal@ege.edu.tr

Preliminary communication
UDC 677.074.1
DOI: 10.31881/TLR.2018.vol1.iss3-4.p114-119.a11
Received 24 October 2018; Accepted 27 November 2018

ABSTRACT
A honeycomb woven fabric was designed and produced on a sampling loom. After weaving cells in the fabric
were opened by polytetrafluoroethylene (PTFE) sticks and an epoxy resin was applied to fabric. For comparison
half of the fabric sample was impregnated with resin without opening the cells. Resulting fabric samples were
subjected to low-velocity impact test by using drop weight impact testing machine, CEAST Fractovis Plus –
7526.000. To evaluate the impact behaviour of the samples the contact force, contact time, deflection, and
absorbed energy values were recorded by data acquisition system (DAS). The energy absorbed by honeycomb
structure was around 7 Joule. The energy absorbed by flat sample, on the other hand, was too low and out of
the detection range of the testing equipment.

KEYWORDS
Honeycomb fabric, Reinforcement, Composite, Energy absorption

INTRODUCTION

Fibrous structures have been used extensively as preforms since they meet successfully the various require-
ments of composite reinforcements. In general, unidirectional and two dimensional (2D) laminated woven
structures are the main forms of reinforcement. Even though these 2D laminated woven structures have
been used with success for over 60 years, their use in many structural applications is limited due to their
high price as a result of labour intense manual lay-up process, their poor impact damage resistance, and
their delamination cracking under impact loading [1,2]. In order to overcome these limitations the devel-
opment of advanced 3D textile structures has gained great attention over the past 40 years. Advanced 3D
textile structures offer structural integrity and fibre continuity by providing multiaxial in-plane and out-of-
plane fibre orientation [3, 4].
One of the advance d 3D textile structures is 3D honeycomb structure. This structure has the geometry of a
honeycomb to allow the minimization of the material used to reach minimal weight and maximum strength.
Thus the composites reinforced with honeycomb structure are light weight, energy absorbent, and strong
[5, 6]. Chen et al. [7, 8] studied honeycomb fabrics and defined them based on the number of fabric layers
involved and the lengths of the free and bonded cell walls. A free cell wall is created by one layer of fabric.
A bonded cell wall is created by combining two adjacent fabric layers. By arranging the length of the free
and bonded cell walls the size of the cells can be adjusted. In another study, the mathematical modelling of

114 www.textile-leather.com
Fabrication of Woven Honeycomb Structures for Advanced Composites
using the multilayer principle [9]. The 300 denier (335F96T) polyester filament yarn was used after
  plied with a twist of 140 turns / meter. The fabric had four layers and the adjacent layers were
    BAŞAL BAYRAKTAR
  combined          G et al.atFabrication
           and separated       arranged of  Woven Honeycomb
                                          intervals             Structures...
                                                    (Figure 1). The  peg plan TEXT LEATH
                                                                                of the   REV 1is(3-4)
                                                                                       weave     given2018 114-119.
                                                                                                        in Figure
  2. The vertical lines indicate the heald shafts, and the horizontal lines indicate the wefts. Grey
honeycomb    structurethat
  squares represent     wasthe
                             studied
                                healdand anwill
                                      shaft algorithm   was
                                                be lifted   created
                                                          during the for theinsertion.
                                                                      weft    computerized
                                                                                       Open design
                                                                                            spaces and manu-
                                                                                                   between
facture of this type of fabrics [6].
  layers allowed to obtain a 3D structure with honeycomb shaped cells in the cross-section with the
In this study a honeycomb woven fabric was designed and produced and the impact resistance of the
  non-flat top and bottom surfaces.
composite structure reinforced by this fabric was determined.

                                Figure 1. Cell openings in honeycomb fabric design
                                  Figure 1. Cell openings in honeycomb fabric design

EXPERIMENTAL
Production of Honeycomb Fabric

A honeycomb woven fabric was designed
and produced on a CCI Evergreen S8900
sample loom using the multilayer principle
[9]. The 300 denier (335F96T) polyester
filament yarn was used after plied with a
twist of 140 turns / meter. The fabric had
four layers and the adjacent layers were
combined and separated at arranged
intervals (Figure 1). The peg plan of the
weave is given in Figure 2. The vertical
lines indicate the heald shafts, and the
horizontal lines indicate the wefts. Grey
squares represent that the heald shaft will
be lifted during the weft insertion. Open
spaces between layers allowed to obtain
a 3D structure with honeycomb shaped
cells in the cross-section with the non-flat
top and bottom surfaces.

Production of Composite

The honeycomb fabrics are in a flat form
with close cells when they leave the loom
due to the nature of weaving. In order to
turn fabric into a 3D honeycomb struc-
ture polytetrafluoroethylene (PTFE) sticks                                       Figure 2. Figure
                                                                                           Peg plan
                                                                                                  2. Peg plan

                                               Production of Composite
                                                                                            www.textile-leather.com 115
                                                    The honeycomb fabrics are in a flat form with close cells when they leave the loom due to the
                                               nature of weaving. In order to turn fabric into a 3D honeycomb structure polytetrafluoroethylene
                                               (PTFE) sticks were inserted into the top and bottom rows of the tunnels before impregnation (Figure
Fabrication of Woven Honeycomb Structures for Advanced Composites
BAŞAL BAYRAKTAR G et al. Fabrication of Woven Honeycomb Structures... TEXT LEATH REV 1 (3-4) 2018 114-119.
                            GRUM GRUM
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were inserted into the top and bottom rows of the tunnels before impregnation (Figure 3). Then, an epoxy
0   0
 C for
resinCmix
        90
        for(FiberMak
             minutes.
             90 minutes.For For
                            comparison
                       Compositescomparison
                                   F-1564somesome
                                          Epoxyfabric
                                                    fabric
                                                 Resin were
                                                       andwere
                                                             impregnated
                                                           F-3486impregnated
                                                                           with
                                                                   Hardener)   with
                                                                             wasresin
                                                                                    resin
                                                                                       in flattened
                                                                                  applied toinboth
                                                                                               flattened
                                                                                                       form
                                                                                                    sides ofform
                                                                                                             the
fabric
withoutusing
    without   aplacing
         placingpaintbrush.
                  the sticks.Curing was carried out in an autoclave at 100 C for 90 minutes. For comparison
                       the sticks.
                                                                          0

some fabric were impregnated with resin in flattened form without placing the sticks.

               Figure 3A.Honeycomb fabric                                        3B. Fabric reinforced with PTFE sticks
                FigureFigure
                        3A.Honeycomb
                             3A.Honeycomb
                                      fabricfabric                         3B. Fabric
                                                                                3B. Fabric
                                                                                      reinforced
                                                                                           reinforced
                                                                                                 with with
                                                                                                      PTFE PTFE
                                                                                                           stickssticks

Drop
Drop Weight
   Drop
     Weight  Impact
        Weight
            Impact
               ImpactTest
                   TestTest

The samplesThe Thewere
                samples  subjected
                     samples
                           werewere   tosubjected
                                          low-velocity
                                  subjected               impactimpact
                                                to low-velocity    testimpact
                                                     to low-velocity    bytest
                                                                            using
                                                                                by drop
                                                                                testusing  weight
                                                                                      by using     impact
                                                                                            dropdrop
                                                                                                 weightweighttesti
                                                                                                           impact ngtesting
                                                                                                                impactmachine,
                                                                                                                         testing
CEAST Fractovis Plus – 7526.000. The impact tests were performed by using hemispherical steel impactor
machine,
     machine,CEASTCEAST
                     Fractovis
                           Fractovis
                                  PlusPlus
                                        – 7526.000.
                                             – 7526.000.
                                                       The The
                                                            impact
                                                                 impact
                                                                     teststests
                                                                           werewere
                                                                                  performed
                                                                                        performed
                                                                                                by using
                                                                                                     by using
                                                                                                            hemispherical
                                                                                                                 hemispherical
tup of 12.7 mm diameter with a total mass of 5.02 kg. The maximum loading capacity of the impactor was
steel
22.4steel
       impactor
      kN.   impactor
                   tup of
            According   tup
                         to12.7
                              of 12.7
                             ASTM mm   mm
                                        diameter
                                     D3763,  diameter
                                                    withwith
                                               the clampeda total
                                                               a total
                                                                  massmass
                                                               specimens of were
                                                                            5.02
                                                                             of 5.02
                                                                                  kg.  The
                                                                                        kg. The
                                                                                   impacted maximum
                                                                                                maximum
                                                                                               with     loading
                                                                                                     impact   loading
                                                                                                                   capacity
                                                                                                               energy  capacity
                                                                                                                        level of
of
10the
   J of
      at impactor
         the
          roomimpactor
                     was was
                          22.422.4
                 temperature.   kN.
                                  TheAccording
                                      kN.  According
                                        test       to ASTM
                                             velocity   to ASTM
                                                        was   D3763,
                                                             1.99 D3763,
                                                                  m/s. the clamped
                                                                           the clamped
                                                                        In order       specimens
                                                                                            specimens
                                                                                  to evaluate   thewere  were
                                                                                                     impactimpacted
                                                                                                                impacted
                                                                                                               behaviorwith
                                                                                                                          ofwith
                                                                                                                             the
samples,
impact
     impact parameters
          energy
               energy     ofsuch
                   levellevel10ofJas
                                   atthe
                                  10  J atcontact
                                      room room     force, contact
                                             temperature.
                                                   temperature.     time,
                                                              The The
                                                                   test    defl
                                                                        test    ecti
                                                                         velocity
                                                                             velocity
                                                                                  wason,was
                                                                                         and1.99
                                                                                         1.99 absorbed
                                                                                              m/s.m/s.    energy
                                                                                                    In order
                                                                                                         In  order values
                                                                                                               to evaluate were
                                                                                                                    to evaluate
recorded by data acquisition system (DAS) during the impact test.
the impact
     the impactbehavior
                    behavior
                           of the
                                of samples,
                                    the samples,parameters
                                                     parameters
                                                              suchsuch
                                                                    as the
                                                                         as contact
                                                                            the contactforce,
                                                                                            force,
                                                                                              contact
                                                                                                   contact
                                                                                                        time,time,
                                                                                                                deflection,
                                                                                                                     deflection,
and and
    absorbed
RESULTS absorbed
          ANDenergy
                 energy
                    values
                        values
               DISCUSSION  werewere
                                recorded
                                    recorded
                                         by data
                                             by data
                                                 acquisition
                                                     acquisition
                                                             system
                                                                 system
                                                                     (DAS)
                                                                        (DAS)
                                                                           during
                                                                               during
                                                                                  the impact
                                                                                      the impact
                                                                                             test.test.

In this study a honeycomb woven fabric was produced using four layers. The resulting fabric cell has a height
RESULTS
     RESULTS
of 6mm,    ANDAND
           free DISCUSSIONS
                wall  DISCUSSIONS
                     length of 5 mm, bonded wall length of 5 mm and an opening angle of 530 (Figure 4).
       In this
           In this
               study
                   study
                     a honeycomb
                         a honeycomb
                                  woven
                                     woven
                                        fabric
                                            fabric
                                               was was
                                                   produced
                                                       produced
                                                            usingusing
                                                                   fourfour
                                                                        layers.
                                                                            layers.
                                                                                The The
                                                                                    resulting
                                                                                        resulting
                                                                                              fabric
                                                                                                  fabric
cell has
     cell ahas
            height
               a height
                   of 6mm,
                        of 6mm,
                            free free
                                  wallwall
                                      length
                                           length
                                              of 5 of
                                                   mm,5 mm,
                                                        bonded
                                                            bonded
                                                               wallwall
                                                                   length
                                                                        length
                                                                           of 5 of
                                                                                mm 5 mm
                                                                                     and and
                                                                                         an opening
                                                                                             an opening
                                                                                                    angle
                                                                                                        angle
of 53of0 (Figure
          530 (Figure
                  4 ). 4 ).

                                                           Figure 4 Cell size
                                                            Figure 4 Cell size

116 www.textile-leather.com
Fabrication of Woven Honeycomb Structures for Advanced Composites
BAŞAL BAYRAKTAR G et al. Fabrication of Woven Honeycomb      Structures... TEXT LEATH REV 1 (3-4) 2018 114-119.
                                                     Figure 4 Cell size

                                                      Figure 5. Honeycomb fabric
                                                      Figure 5. Honeycomb fabric

 The fabric turned into a honeycomb composite by applying an epoxy resin mix (Figure 5). Before resin appli-
          The infabric
 cation cells            turned
                  the fabric     into
                              were      a honeycomb
                                     opened      using PTFE  composite
                                                               sticks. Halfbyofapplying
                                                                                the fabricanwas
                                                                                              epoxy
                                                                                                 left inresin
                                                                                                          the flmix  (Figure
                                                                                                                attened   form 5).for
 comparison.
   Before resinThen,    the fabrics
                   application  cellswere
                                       in thesubjected    to low
                                                 fabric were       velocity
                                                               opened        impact
                                                                         using   PTFEtest. In aHalf
                                                                                      sticks.   honeycomb       composite
                                                                                                    of the fabric    was leftstruc-
                                                                                                                                in
 ture, the impact energy is absorbed not only by the elastic and plastic deformation of the fabric structure
   the flattened form for comparison. Then, the fabrics were subjected to low velocity impact test. In a
 but also the collapse of the cells. If the honeycomb structure cannot absorb the whole energy the force is
   honeycomb composite structure, the impact energy is absorbed not only by the elastic and plastic
 transmitted to structure underneath the composite and cause damage. Thus the energy absorbed by the
   deformation
 structure          of cant.
            is signifi the fabric
                             Figurestructure
                                     6(a) shows    but
                                                     thealso  the collapse
                                                          composite           of the
                                                                       structure      cells.
                                                                                   made       If the
                                                                                           from   the honeycomb
                                                                                                       designed fabric structure
                                                                                                                           without
 opening
   cannot the   cells.the
           absorb       Aswhole
                           seen from
                                  energy thethefigure  the
                                                   force is composite
                                                            transmittedstructure     could
                                                                            to structure     not resist the
                                                                                           underneath      the impact
                                                                                                                compositeforce
                                                                                                                             andand
 was broken apart. The test result was out of the detection range of the impact tester. Figure 6(b) shows
   cause damage. Thus the energy absorbed by the structure is significant. Figure 6 (a) shows the
 the composite structure made from the designed fabric with the open cells. The damage was restricted to
   composite     structure      GRUM
                             made        GRUM
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                                                               ofWeaveandDensities…
                                                                      ofWeaveandDensities…
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 a small area. Clearly,    open cellfrom
                                      structure     designed
                                                    absorbed fabric
                                                                some of without
                                                                           impactopening
                                                                                   energy. the cells. As seen from the
   figure the composite structure could not resist the impact force and was broken apart. The test result
   was out of the detection range of the impact tester. Figure 6(b) shows the composite structure made
   from the designed fabric with the open cells. The damage was restricted to a small area. Clearly,
   open cell structure absorbed some of impact energy.

                      a) Sample with closed cells                                  b) Sample with open cells
                 a)sample
                       a)sample
                          with closed
                                  with cells
                                       closed cells                                b) Sample
                                                                                         b) Sample
                                                                                             with open
                                                                                                    withcells
                                                                                                         open cells
                                           Figure 6. Fabric samples after impact test
                                             Figure 6.
                                                    Figure
                                                       Fabric6.samples
                                                                Fabric samples
                                                                        after impact
                                                                                after impact
                                                                                      test test

 Figure 7 shows the contact load–displacement plots of honeycomb composite structure with open cells
 at 10Figure
       J impact    energy.
              Figure
               7 shows        Thecontact
                         7 shows
                            the   load–displacement
                                   the contact           curves plots
                                          load–displacement      show of
                                                 load–displacement     anhoneycomb
                                                                           increase
                                                                       plots         of the
                                                                              of honeycomb  load
                                                                                         compositeup structure
                                                                                                      to a maximum
                                                                                                composite         with load
                                                                                                             structure   with
 termed
open      peak
      cells
      open      10load,
            atcells       followed
                    Jatimpact
                         10 J impactbyenergy.
                                energy. aThe
                                          drop  afterload–displacement
                                                       the peak load.
                                              load–displacement
                                                The                    Thecurves
                                                                    curves  peak load
                                                                            show   an
                                                                                   show was  805ofN.the
                                                                                      increase
                                                                                          an increase The
                                                                                                        of area
                                                                                                         load
                                                                                                           theup  under
                                                                                                                load  a the
                                                                                                                   to up  to a
 curve gives the energy absorption. Calculated energy was 7,043 Joule. Unfortunately, close cell structure
maximum
      maximum
            load termed
                     load termed
                              peak load,
                                     peak followed
                                           load, followed
                                                      by a drop
                                                            by a after
                                                                 drop the
                                                                       afterpeak
                                                                              the load.
                                                                                   peak The
                                                                                         load.peak
                                                                                               The load
                                                                                                    peakwasload805wasN.805 N.
 did not produce any results since the values measured were too low for the test equipment.
The area
      The under
             area under the curve
                               the curve
                                     gives gives
                                             the energy
                                                   the energy
                                                            absorption.
                                                                  absorption.
                                                                          Calculated
                                                                                 Calculated
                                                                                        energyenergy
                                                                                                 was 7,043
                                                                                                        was 7,043Joule. Joule.
Unfortunately,
     Unfortunately,
               close cell
                     closestructure
                            cell structure
                                     did not
                                           didproduce
                                                not produce
                                                       any results
                                                             any results
                                                                   since the
                                                                         sincevalues
                                                                                the values
                                                                                     measured
                                                                               www.texti   measured
                                                                                                were too
                                                                                                      were117
                                                                                         le-leather.com    too
low forlow
         thefor
              test
                theequipment.
                    test equipment.
Fabrication of Woven Honeycomb Structures for Advanced Composites
The area under the curve gives the energy absorption. Calculated energy was 7,043 Joule.
        Unfortunately, close cell structure did not produce any results since the values measured were too
BAŞAL BAYRAKTAR G et al. Fabrication of Woven Honeycomb Structures... TEXT LEATH REV 1 (3-4) 2018 114-119.
        low for the test equipment.

                             Figure 7. Load–displacement curve for low-velocity impact test
                                    Figure 7. Load–displacement curve for low-velocity impact test

CONCLUSION

This is a preliminary work to investigate the potential of honeycomb structures in advanced composites. In
this study we designed and produced a four layer honeycomb fabric as reinforcement material and inves-
tigate the impact resistance of the composite structure made from this preform with and without opening
the cells. The composite structure with closed cells did not resist the impact force and was broken apart.
The test equipment could not detect any signal. The hollow structure created by opening the cells, on the
other hand, resisted to impact force and absorbed an energy of 7,043 Joule. The test conducted in this study
was limited due to the time constrains. The further experiments and statistical analysis will be carried out
to found out the effect of impact site on results.
We believe that honeycomb structures have great the potential in advanced composites. Their properties
should be further explored. It is not difficult to weave this type of structure by a regular loom but opening
up cells is time consuming job. A simplified method would increase their usage.

Acknowledgements
The authors greatly appreciate the financial support provided by Ege University Research Foundation (Project
No: 17-MUH-056).

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[1]   Mouritz AP, Bannister MK, Falzon PJ, Leong KH. Review of applications for advanced three-dimensional
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[2] Hu JL. 3-D fibrous assemblies: properties, applications and modeling of three-dimensional textile
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[3]   Cherif C. Textile materials for lightweight constructions technologies - methods - materials – properties.
      Berlin: Springer; 2016. 188-189 p.
[4] Behera BK, Hari PK. Woven Textile Structure. Cambridge (UK): Woodhead Publishing Series in Textiles;
    2010. 3-8 p.

118 www.textile-leather.com
Fabrication of Woven Honeycomb Structures for Advanced Composites
BAŞAL BAYRAKTAR G et al. Fabrication of Woven Honeycomb Structures... TEXT LEATH REV 1 (3-4) 2018 114-119.

[5] Chen X. Advances in 3D Textiles, Cambridge (UK): Woodhead Publishing Series in Textiles; 2015.
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[7] Chen X, Sun Y, Gong X. Design, manufacture, and experimental analysis of 3D honeycomb textile
    composites, part I: design and manufacture. Textile Research Journal. 2008 Sep;78(9):771–781.
[8] Chen X, Sun Y and Gong X. Design, manufacture, and experimental analysis of 3D honeycomb textile
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The paper presents a preliminary work on honeycomb woven structures for advanced composites, first
presented at the 8th International Textile Conference, Tirana, Albania, on October 18-19, 2018. Experimental
part of the study offered limited information. The paper presents a preliminary communication. Future
research will produce more results on top of which an original scientific paper will be published.

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