Ph.D. thesis defense presentation dated April 19th, 2016 Develop a viable method for manufacturing all composite lattice core sandwich panels. Investigate their mechanical properties and failure mechanism through a series of experimental tests. Develop analytical models for predicting the elastic stiffness and collapse strength as a function of the constituent material properties and core geometry. Carry out numerical simulations for comparison with experimental results and to validate the analytical models.

1. The Mechanical Properties of Composite
Lattice Structures
Hassan Ziad Jishi
Advisors:
Professor: Wesley J. Cantwell
Assistant Professor: Rehan Umer
Khalifa University of Science Technology and Research
April 19th 2016
Aerospace Research and Innovation Center (ARIC)Aerospace Research and Innovation Center (ARIC)

2. Structure of the talk
• Research Objectives
• Background
• Hybrid core studies
• Lattice structures
• Analytical solutions
• FE modeling
• Conclusions
• Future work
4/27/2019 2

3. Objectives
• Develop a viable method for manufacturing all composite lattice core sandwich panels.
• Investigate their mechanical properties and failure mechanism through a series of experimental
tests.
• Develop analytical models for predicting the elastic stiffness and collapse strength as a function of
the constituent material properties and core geometry.
• Carry out numerical simulations for comparison with experimental results and to validate the
analytical models.
4/27/2019 3

4. Introduction
• Sandwich structures are typically composed of two thin, but stiff skins with a light weight, thick
core positioned between them.
• Sandwich panels provide excellent mechanical properties at minimal weight.
4/27/2019 4
Laminated composites Metal
Honeycomb structure Foam type materialBalsa wood
Solid material Core thickness = t
Stiffness 1.0 7.0
Flexural strength 1.0 3.5
Weight 1.0 1.03
For twice the thickness:
700% the rigidity
350% the strength
and only 3% increase in weight
Skin
Core
Skin

5. Introduction
4/27/2019 5
• Composites represent fifty percent (by weight) of the 787 aircraft structure.
• Many components have been based on honeycomb or foam core sandwich structures.
Source: Boeing

6. • Currently, there is a strong interest in developing ultra lightweight, high-strength structures such as
lattice architectures for use in aerospace design.
• Lattice truss topologies have been investigated and shown to exhibit stiffness and strength properties
that scale linearly with relative density, ρ.
Kagome
Pyramidal
Honeycomb
Introduction
4/27/2019 6Source: M. F. Ashby, The properties of foams and lattices, Philos. Trans. A. Math.
Phys. Eng. Sci., vol. 364, pp. 15–30, 2006.
Strength ∝ ρ
Strength ∝ ρ1.5

7. Introduction
• In recent years, there has been a growing interest in manufacturing and characterizing the properties of
metallic lattice structures.
(a) Aluminum octet truss structure (b) copper 3D kagome structure. Source: Wadley Research GRP
• Structures with metallic truss cores can be stiff, strong and lightweight as state-of the art structural panels
(honeycomb cores) in addition to multi-functional capability.
• In this work, attention is focused on developing composite lattice structures that should, in principle, out-
perform their metallic counterparts.
4/27/2019 7

8. • Ashby diagram of Strength vs. Density chart for engineering materials.
• Composite lattice structures offer the potential to fill the gap between the currently available
materials and the unattainable material space.
Density [Mg/m3]
Strength(MPa) Introduction
4/27/2019 8
K. Finnegan, G. Kooistra, H. N. G. Wadley and V. S. Deshpande,
The compressive response of carbon fiber composite pyramidal
truss sandwich cores, Int. J. Mater. Res., vol. 98, pp. 1264–1272,
2007.
Pyramidal structure was formed by snap-
fitting the members together and the skins
were then bonded.
CFRP lattice
(Theoretical limit)

9. • The study started by drilling holes into a PET foam core. Fibers were then inserted into the perforations
in an attempt to improve the mechanical properties of the panel.
• The sandwich panels were then manufactured using the vacuum assisted resin transfer molding
(VARTM) process.
• This was then extended to look at the possibility of removing the ‘core’ by adopting a lost mold
technique.
Proof of concept: Lattice fabrication
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Vertical drill
Circular holes
Core
Fiber tows
Resin flow direction
1
1
2
3
4
5
6
7
8
Release coated mold
Sealant tape
Vacuum bagging film
Wax block
Peal Ply
Skin
Flow Media
Core
Vacuum pump Resin reservoir
2
3
4
5
7
8
6
Resin
trap

10. Hybrid core panels
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Skin
Hybrid core
PET foam
GFRP truss

11. Experimental Procedure: Materials
• Core Material: Polyethylene-Terephthalate (PET)
– Nominal density: 130 kg/m3
– Thickness: 20mm
• Reinforcing Skin: Unidirectional E-glass fabric
– Areal density: 600 g/m2
– Number of layers: 4
• Resin System: Epoxy Resin with a fast hardener
– Weight mix ration: 100 Resin : 26 Hardener
– Geltime: 30 minutes @ 25oC
11

12. Hybrid core sandwich panel
• Tests were undertaken on the six types of sandwich structure:
– Plain foam core.
– Perforated foam core with holes arranged in a 25.4 mm and 12.7mm
square pattern.
– Perforated foam core with holes reinforced with glass fiber tows
arranged in a 25.4 mm and 12.7 mm square pattern:
• fiber volume fraction 1.5% and 3%
• Continuous fiber tow and individual

13. 4/27/2019 13
25 mm
25 mm

14. 1. Distribution medium, was used to facilitate the flow of resin.
14
Experimental Procedure: VARTM Process
Preform assembly
Vacuum pump
Resin trap
2. The edges of the mold were sealed using a vacuum bagging
material and a sealant tape.
3. The mold was then infused with resin under vacuum.
Peel

15. • Compression tests were carried out by loading the specimens with an edge length of 50 mm
between circular steel plattens at a crosshead displacement rate of 5 mm/min.
• Typically, four repeats of each core configuration were tested.
Hybrid core sandwich panel: Compression tests
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16. Results : Post-manufacture visual assessment
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• To assess the degree of resin filling,
several panels were sectioned along a
plane close to the perforations using a
water-cooled diamond tipped saw.
• All samples with perforations, including
those containing fibers, appear to be
completely filled with resin.
Cross sections of manufactured samples with filled holes. (a) Materials B, (b)
Materials C, (c) Material D-D, (d) Material D-S, (e) Material E-D, (f) Material E-S,
(g) Material F-D, (h) Material F-S.
Vf = 3%
Vf = 0%Vf = 0%
Vf = 3%
Vf = 3%
Vf = 1.5%
Vf = 1.5%
Vf = 1.5%

17. 17
Hybrid core: Compression Tests and Results
• Material C, based on neat resin columns, offers the highest compression strength.
• Adding fibers to the resin columns, D-S, resulted in a decrease in compression strength, possibly due to
the presence of micro-voids between individual fibers.
• Fiber-reinforced perforations served to increase the compression strength of the foam.
0
1
2
3
4
5
6
7
8
A B C D-S E-S F-S
CompressionStrength(MPa)
Material
Vf = 1.5%
Vf = 0%
Vf = 0%
Vf = 1.5%

18. Lattice structures
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19. Experimental Procedure: Lost Mold Procedure materials
• Core Materials:
– A high quality wax block, or
– Dissolvable material (Slab of Salt)
• Reinforcing fabric sheet and Tows:
– Could be carbon, glass, natural fibers, etc.
• Resin System: Epoxy (Prime 20LV) with a fast hardener:
– Weight mix ratio: 100 Resin : 26 Hardener
– Geltime: 30 minutes @ 25oC
19

20. • The lost mold is prepared by drilling an array of holes reflecting the final configuration of the lattice
structure.
• Fibers were then fed through the array of holes (this can be via either a manual or an automated
process).
20
Experimental Procedure: Lost Mold Procedure
(b)(a) (c) (d)
(a) Vertical column, (b) modified pyramidal truss, (c) BCCz lattice and (d) an octet structure.

21. Experimental Procedure: Lost Mold Procedure
• Two weaving patterns were adopted and these are shown schematically
• The fiber volume fraction within an individual hole was varied by increasing/decreasing the number of
fiber tows during the threading process.
21
(a) (b)
Skin
Core
Fibre
tows
25 mm
fiber tow
Facesheet
Core

22. 1. Distribution medium, was used to facilitate the flow of resin.
22
Experimental Procedure: VARTM Process
Resin flow direction
1
1
2
3
4
5
6
7
8
Release coated mold
Sealant tape
Vacuum bagging film
Wax block
Peal Ply
Skin
Flow Media
Core
Vacuum pump Resin reservoir
2
3
4
5
7
8
6
Resin
trap
Preform assembly
Vacuum pump
Resin trap
2. The edges of the mold were sealed using a vacuum bagging
material and a sealant tape.
3. The mold was then infused with resin under vacuum.

23. • The mold was then removed, either by dissolving it (salt) or by
heating in an oven (wax).
• A schematic diagram of the entire process :
23
Experimental Procedure: Lost Mold Technique
Skin
Infusion process
(VARTM)
Cure and Post cure
Skin
PET foam
Lattice
Core removal by
melting or heating
Skin
Lattice
Vertical drill
Circular holes
Core (salt, wax
or PET foam)
Fiber tows
1
2
3
4

24. Vertical, pyramidal, and octet lattice studies
• The composite column cores were manufactured using a lost mold procedure.
• Individual and a series of vertical columns were manufactured.
• The two weaving patterns were adopted.
24
𝜌 = 16.3% 𝜌 = 26.7% 𝜌 = 30.4% 𝜌 = 34.9%
Config. (A) Config. (B)

25. Vertical, pyramidal, and octet lattice studies
• Sandwich panels based on a pyramidal core, and a modified pyramidal core
• fibers were woven through holes with diameters of 3 mm, according to Config. A.
• Octet truss structures with strut diameters of 4 mm were prepared by drilling an array of holes through 56
mm thick salt blocks
4/27/2019 25
(a) a pyramidal structure and (b) a modified pyramidal structure,
(a) (b)
Config. (A)

26. BCC, BCCz, FCC and F2BCC lattice studies
• Four, all-composite lattice designs, were also considered, these being the BCC, BCCz, FCC and F2BCC
designs. All prepared using a lost-mold procedure.
• fibers were woven through holes according to Config. B.
4/27/2019 26
(a) (c)(b) (d)
(a) the BCC unit cell and (b) the BCCz unit cell (c) the FCC unit cell and (d) the F2BCC lattice
Wax
Core
Skin
Fibre tows
a) b)b)
(a) Schematic drawings of the procedure used to thread the samples. (b) Threaded sample.

27. Lattice core sandwich panel: Compression tests
• The quasi-static properties of the lattice structures were evaluated by loading the specimens in an
Instron 5969 at a crosshead displacement rate of 2 mm/min.
• Typically, three to four repeat repeats of each core configuration were tested.
4/27/2019 27
Load
Compression
platens
Specimen
Load

28. Analytical Modeling
• Analytical solutions for the initial modulus (E) and strength (𝝈 𝒄) properties under conditions of
compression loading were developed.
• The elastic deformation of a single truss was examined using beam theory. The results are
extended to evaluate the effective properties of the lattice.
• Collapse strength due to plastic microbuckling and elastic buckling failure modes were considered
in the analysis.
4/27/2019 28
wl cos2
wl cos2
l
d
Truss
section
wlsin
w

Applied force F
Applied force F
(a)
(b)
x
ye2
e1

29. Analytical Modeling
• The analytical calculations are then compared with experimental data from the quasi-static tests and
finite element model predictions.
4/27/2019
29
l
wd
h
l
w
d
l
wd
d
w
l
wl cos2
wl sin2
d
w
l
wl cos2
wlsin2
wd cos2
d
wlsin2
l
α
w
r
Vertical
Pyramidal
M. Pyramidal
BCC
BCCz
F2BCC
StrengthInitial modulus

30. Finite Element Analysis
• Finite element analyses were performed to predict the response of the lattice cores under
compression loading.
• The simulations were carried out using the ANSYS FE package.
4/27/2019 30
P, δ
P = Load
δ = Displacement
Deformable beam
elements representative
of the lattice core
Top surface: fully constrained except in
translation in the through-thickness direction
Bottom surface: fully constrained in
translation and rotation
P, δ
P, δP, δ
• The model set-up, involved applying loading and
boundary conditions on a single unit cell.
• Models used Timoshenko beam element, BEAM188
element in ANSYS.

31. Finite Element Analysis
• Hashin’s failure criteria was considered in the analysis.
• Four failure modes are included in Hashin’s criteria, these being failure due to:
𝜎i denote the stress components
𝜎𝑥𝑡,𝑥𝑐
𝑓
, 𝜎 𝑦𝑡,𝑦𝑐
𝑓
and 𝜎𝑥𝑦,𝑦𝑧
𝑓
are tensile, compressive and shear allowable strengths.
4/27/2019 31
1. fiber tension (𝜎 𝑥 > 0)
2. fiber compression (𝜎 𝑥 ≤ 0)
3. Matrix tension (𝜎 𝑦 > 0)
4. Matrix compression (𝜎 𝑦 ≤ 0)
2
11
1 failure
1 no failureCX
   
  
 
2
11
1 failure
1 no failureCX
   
  
 
𝜉 =
𝜎𝑦 + 𝜎𝑧
𝜎𝑦𝑡
𝑓
2
+
𝜎𝑦𝑧
2
− 𝜎𝑧 𝜎𝑦
𝜎𝑦𝑧
𝑓 2 +
𝜎𝑥𝑦
2
+ 𝜎𝑥𝑧
2
𝜎𝑥𝑦
𝑓 2
1
𝜎𝑦𝑐
𝑓
𝜎𝑦𝑐
𝑓
2𝜎𝑦𝑧
𝑓
2
− 1 𝜎𝑦 + 𝜎𝑧 +
𝜎𝑦 + 𝜎𝑧
2𝜎𝑦𝑧
𝑓
2
+
𝜎𝑦𝑧
2
− 𝜎𝑧 𝜎𝑦
𝜎𝑦𝑧
𝑓 2 +
𝜎𝑥𝑦
2
+ 𝜎𝑥𝑧
2
𝜎𝑥𝑦
𝑓 2
2
11
1 failure
1 no failureCX
   
  
 
2
11
1 failure
1 no failureCX
   
  
 

32. Results : Post-manufacture visual assessment
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32
• Visual inspection indicates successful infusion of all of the struts.
10 mm
Pyramidal structure Modified pyramidal structure Column truss
10 mm
10 mm
Structure based on three octet unit cells Octet truss unit cell

33. Results : Post-manufacture visual assessment
4/27/2019
33
• The lattices are generally of a high quality, with there no evidence of any significant defects on the
surfaces of the samples.
BCC FCCF2BCCBCCz
From left to right: photographs of the BCCz, the F2BCC, the BCC and FCC lattice structures following manufacture.

34. Micrograph Analysis
4/27/2019 34
• Typical cross-sections of individual struts following manufacture
• An examination of the figure indicates that the struts have been successfully infused with resin
during the manufacturing process.
Vf =0.28
3mm
Vf =0.28
4mm2.5mm
Vf =0.28Vf =0.51
2mm
(a) (b) (c) (d)
250 µm 300 µm 375 µm 500 µm

35. Compression Tests on Individual Columns
4/27/2019 35
Config. (A) Config. (B)
• Typical stress-strain traces following compression tests on individual struts with diameters of 2.5 and
3.0 mm. (Vf = 42%)
Config. (A): failure occurred as a result of interfacial failure between the horizontal tows
and the inner skin. Fracture of this interface leads to lateral movement.
Config. (B): anchoring the fibers to the skins leads to a significant increase in strength and
much greater energy absorption
0
50
100
150
200
250
300
0 0.05 0.1 0.15 0.2 0.25 0.3
Stress[MPa]
Strain [mm/mm]
(B)(A)
A
B
0
50
100
150
200
250
300
0 0.05 0.1 0.15 0.2 0.25 0.3
Stress[MPa]
Strain [mm/mm]
A
B
(B)(A)

36. Compression Tests on Individual Columns
• Variation of compression strength with slenderness ratio for single columns
• Compression strength increases with decreasing SR and/or increasing Vf
• Euler model accurately predicts the strength of the samples based on intermediate and high values off SR.
• The model breaks down for the 4 mm diameter samples based on fiber volume fractions of 0.28 and 0.42. Here,
failure was associated with crushing at one end of the column rather than buckling.
36

37. Compression Tests on the Composite Truss Cores
• Typical stress-strain curves for truss cores based on 3 and 4 mm diameter columns.
• As was the case for the simple columns, threading the fibers through the skins serves to greatly enhance the mechanical
properties of the core.
• Loading Configuration A (i) results in skin-core interfacial failure, causing the columns to splay outwards as the crosshead
displacement increases.
• Configuration B (ii) of 3mm samples failed as a result of some initial buckling failure.
• Crushing at the truss extremities was the predominant mode of failure in the 4 mm ‘B’ samples.
37
0
10
20
30
40
50
60
70
0 0.05 0.1 0.15 0.2 0.25 0.3
Stress[MPa]
Strain [mm/mm]
A
B
(A) (B)
0
10
20
30
40
50
60
70
80
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
Stress[MPa]
Strain [mm/mm]
B
A
(A) (B)

38. Compression Tests on the Composite Truss Cores
• Specific compression strength vs. slenderness ratio for the truss cores. Vf = 0.28.
• Compression data for both configurations are divided by the relative density.
• Included in the figure are the predictions associated with Euler buckling theory and the finite element analyses.
• The Euler model breaks down at lower values of SR, again due to the fact that failure occurs in a crushing mode,
rather than buckling.
4/27/2019 38
0
50
100
150
200
250
300
350
20 30 40 50 60 70 80 90
SpecificCompressionStrength[MPa]
Slenderness Ratio (SR)
- Euler theory
Experiment (Config. A)
Experiment (Config. B)
FE model
Vf = 28%

39. 4/27/2019
39
Compression Tests on Pyramidal Structures
• Increasing the fiber volume fraction serves to increase the load-carrying capability.
• Agreement between the FE predictions and the experimental data is relatively poor for the modified pyramids, with
the model over-predicting the test results.
• Fiber tows were not anchored to the skins (Configuration A).
• FE predictions are more representative of the mechanical performance of pyramids based on Configuration B.
39
0
10
20
30
40
50
60
70
80
Vf=0.06 Vf=0.12 Vf=0.06 Vf=0.12
SpecificCompressionStrength(MPa)
Pyramidal core Modified pyramidal core
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
Vf = 3.5% Vf = 7%
SpecificCompressionStrength(MPa)
Experiment
FE model

40. • Fiber tows did not connect through the skins and were not inter-twined at the mid nodes.
(Configuration A)
4/27/2019 40
Compression Tests on the Octet Structures
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
Vf = 3.5% Vf = 7% Vf = 11%
SpecificCompressionStrength(MPa)
Experiment
FE model

41. • Stress-strain traces following tests on the BCC and BCCz lattice structures showing reasonably high level of
repeatability.
• The lattices begin to fail, typically at the uppermost or lowermost nodes between the core and the skin.
• This second peak is associated with loading the lower pyramid in the lattice once the crosshead has reached roughly
the mid-point of the lattice structure.
• In BCCz structure, it is clear that the inclusion of four vertical struts greatly enhances the compression strength of
the lattice.
Compression tests on BCC, BCCz, FCC and F2BCC lattice
4/27/2019
41
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
0.0 0.2 0.4 0.6 0.8 1.0
Stress[MPa]
Strain [mm/mm]
ε =
0%
ε =
20%
ε =
40%
0
1
2
3
4
5
6
7
8
9
0.0 0.2 0.4 0.6 0.8 1.0
Stress[MPa]
Strain [mm/mm]
ε = 10%ε = 0% ε = 40%

42. • Stress-strain traces following tests on the FCC and F2BCC lattice structures.
• The initial stress in the FCC structure increases to values of up to 7 MPa, i.e. similar to those observed in the BCCz
lattice.
• Struts fail in a global buckling mode, with some mid-nodes failing, due to the fact that the fibers are not intertwined
at these locations.
• The F2BCC structures offer the highest compression strengths of the four lattices considered in this study with a
peak value of up to 13 Mpa.
Compression tests on BCC, BCCz, FCC and F2BCC lattice
4/27/2019 42
0
2
4
6
8
10
12
14
0.0 0.2 0.4 0.6 0.8 1.0
Stress[MPa]
Strain [mm/mm]
0
2
4
6
8
10
12
14
0.0 0.2 0.4 0.6 0.8 1.0
Stress[MPa]
Strain [mm/mm]
ε = 50%ε = 20%ε = 0%ε = 30%ε = 20%ε = 0%

43. Compression tests on BCC, BCCz, FCC and F2BCC lattice
• Elastic modulus values of the four lattice structures. Excellent agreement between the analytical and finite
element models, but the model over-predict the experimental values.
• Differences are likely due to:
- errors associated with using the crosshead displacement to determine the strain.
- discrepancies between the assumed and actual boundary conditions at the strut-skin interface.
• However, the models correctly predict the general trends in the experimental data.
4/27/2019
43
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
BCC BCCz FCC F2BCC
Young'sModulus(MPa)
Experiment
FE model
Analytical model

44. Compression tests on BCC, BCCz, FCC and F2BCC lattice
• Experimentally-determined values of the compression strength of the four lattices with the predictions offered by
both the analytical analysis and the FE model.
• The F2BCC structure offers the highest strength with the average value being 12 MPa.
• The disparity between the measured and predicted values are likely to be associated with the presence of defects in
the lattices and fiber distortion in the nodal regions.
4/27/2019 44
0
2
4
6
8
10
12
14
16
18
20
BCC BCCz FCC F2BCC
Compressionstrength(MPa)
Experiment
FE model
Analytical model

45. Lost mold procedure
a) Top view of a single skin sandwich structure (S4), b) skin free side of the S4 structure, c) lattice wheel d) Natural fiber reinforced
airofoil, e) Carbon fiber reinforced airofoil and f) Honecomb structures
45
mm
10 mmf)

46. Conclusions
• The potential of the lost mold technique has been demonstrated by successfully manufacturing and
testing of a series of composite lattice core structure.
• Successfully developed analytical models for predicting the elastic stiffness and collapse strength of the
various lattice structures.
4/27/2019 46
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02
Strength(MPa)
Density [Mg/m3]
Pyramidal
M. Pyramidal
Octet
BCC
BCCz
FCC
F2BCC
Vertical
Strength values may be increased by:
• Employing higher values of fiber
volume fraction during the
manufacturing process.
• Automating the process of drilling
and threading.

47. Future work
• Employ higher values of fiber volume fraction during the manufacturing process for improved
mechanical properties.
• Additional testing to be conducted to fully characterize the behavior of the lattice structures under shear,
bending and dynamic compression loading conditions.
4/27/2019 47
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02
Strength(MPa)
Density [Mg/m3]
Pyramidal
M. Pyramidal
Octet
BCC
BCCz
FCC
F2BCC
An Ashby diagram including the FE model
predictions for compression strengths of the
various lattice cores made from a material having
a 51% fiber volume fraction.

48. Publications
• H. Z. Jishi, R. Umer and W. J. Cantwell, The fabrication and mechanical properties of novel composite lattice
structures, Materials & Design, vol. 91, pp.286-293, 2016.
• H. Z. Jishi, R. Umer and W. J. Cantwell, Skin‐core debonding in resin‐infused sandwich structures, Polymer
Composites, 2015. DOI: 10.1002/pc.23494.
• H. Z. Jishi, R. Umer, Z. Barsoum and W. J. Cantwell, The mechanical properties of sandwich structures based on
composite column cores, in the 20th International Conference on Composite Materials (ICCM20), Copenhagen,
Denmark, 2015.
• H. Z. Jishi, R. Umer and W.J. Cantwell, Investigation of Skin-Core Adhesion in Resin Infused Sandwich Panels,
12th International conference on Flow Processes in Composite Materials (FPCM12), Enschede, The Netherlands,
2014.
• H. Z. Jishi, R. Umer, K. Ushijima and W. J. Cantwell, The mechanical properties of composite lattice structures.
Submitted to Journal of Composite Structures, 2016. (under review)
• H. Z. Jishi, R. Umer, Z. Barsoum and W. J. Cantwell, Numerical simulation of continuous fibers composite lattice
structures. (In preparation)
• H. Z. Jishi, R. Umer, S. Rao and W.J. Cantwell Composite lattice structure based on natural fibers. (In preparation)
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49. Acknowledgment
• I would like to acknowledge my advisors Prof. Wesley J. Cantwell and Dr. Rehan Umer for their
help and support.
• I thank Jimmy Thomas and Bitu Scaria for their help in preparing the test specimens.
• Thanks to Dr. Z. Barsoum for his assistance in running the FE simulations.
• The research carried out was made possible by Mubadala Aerospace and Khalifa University
through funding the Aerospace Research and Innovation Center and by Khalifa University for
providing a PhD scholarship.
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50. 4/27/2019
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Thank you
mm