J. J. BRITTO et al.: SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED COMPOSITE STRUCTURE ...
783–791
SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED
COMPOSITE STRUCTURE: EXPERIMENTS AND
FINITE-ELEMENT MODELING
PAMETNA KOMPOZITNA STRUKTURA S STEKLENIMI VLAKNI
OJA^ANE TKANINE S PIEZO EFEKTOM: PREIZKUSI IN
MODELIRANJE NA OSNOVI METODE KON^NIH ELEMENTOV
Jerold John Britto J.
1*
, Vasanthanathan A.
2
, Karthik Vinayaga K.
2
,
Senthil Maharaj P. S. R.
3
1
Department of Mechanical Engineering, Ramco Institue of Technology, Rajapalayam, Tamilnadu, India
2
Department of Mechanical Engineering, Mepco Schlenk Engineering, Sivakasi, Tamilnadu, India
3
Department of Mechanical Engineering, AAA College of Engineering and Technology, Sivakasi, Tamilnadu, India
Prejem rokopisa – received: 2024-08-05; sprejem za objavo – accepted for publication: 2024-10-14
doi:10.17222/mit.2024.1269
This paper deals with an experimental and finite-element investigation of smart polyvinylidene fluoride (PVDF) embedded with
a glass-fabric-reinforced polymer (GFRP) beam structure under vibration. PVDFs are well known stretchy polymer that process
the properties of both piezoelectric and pyroelectric materials. An LDT0-028K PVDF polymer film is proposed in the present
paper. Glass-fiber-reinforced polymer is a lightweight composite material having a high specific strength and specific stiffness,
due to which it has a wide range of applications in the field of smart composite structures. GFRP laminates and beam structures
are fabricated in the present investigation through a vacuum-assisted resin-infusion process (VARIP). Mechanical characteriza-
tion in accordance with ASTM standards were also carried out for the purpose of the estimation of uni-directional mechanical
properties of GFRP, which are a pre-requisite for finite-element simulations. Both the experiments and the finite-element model-
ling were carried out for the smart piezo composite beam structure under forced vibration conditions. The finite-element compu-
tations were incorporated in the present study using ANSYS
®
16.0 Mechanical APDL. The results of the experimental and FEM
investigations show a deviation of around 6.2 %, with the experimental values validating the FEM analysis. Based on the har-
monic response of the smart piezo-composite beam, a micro-energy harvesting study was established with reference to the vary-
ing frequency and voltage.
Keywords: piezoelectric, polyvinylidene fluoride, piezocomposite, glass-fiber-reinforced polymer, finite element method,
ANSYS
®
V ~lanku avtorji opisujejo {tudijo o »pametnem« poliviniliden fluoridu (PVDF; (C2H2F2)n) obdanem s steklom oja~ano
»pametno« polimerno strukturo (GFRP; angl.: glass fabric reinforced polymer). Izdelano strukturo v obliki traku (nosilca) so
analizirali eksperimentalno in modelirali z metodo kon~nih elelmentov (FEM; angl.: Finite Element Method). PVDFs so dobro
znani pro`ni/raztegljivi (angl.: stretchy) polimerni materiali, ki imajo piezo- in piro- elektri~ne lastnosti. Avtorji so za pri~ujo~o
{tudijo porabili LDT0-028K PVDF polimerni film. S steklenimi vlakni oja~an polimer je lahek kompozitni material, ki ima
veliko specifi~no trdnost in togost ter se zato pogosto uporablja na podro~ju »pametnih« kompozitnih struktur. Za pri~ujo~o
raziskavo so GFRP laminate in nosilne strukture izdelali s pomo~jo procesa vakumsko podprtega nalivanja polimerne smole
(VARIP; angl.: vacuum assisted resin infusion process). Nato je sledila mehanska karakterizacija v skladu z ASTM standardom,
zato da so lahko dolo~ili njihove mehanske lastnosti v razli~nih smereh. Njihovo poznavanje je predpogoj za modeliranje s
pomo~jo FEM. Avtorji so izvedli tako eksperimentalne preizkuse kot tudi FEM modeliranje nosilca pametne piezo kompozitne
strukture v pogojih vsiljenih vibracij. Izvedli so kompletne ra~unalni{ke simulacije in izra~une s pomo~jo programskega orodja
ANSYS
®
16.0 Mechanical APDL. Rezultati eksperimentalnih preizkusov in ra~unalni{kega FEM modeliranja so se med seboj
razlikovali za pribli`no 6,2 %. Pri razli~nih frekvencah in napetostih so na osnovi harmoni~nega odgovora pametnega piezo
kompozitnega nosilca izvedli mikro energijsko {tudijo.
Klju~ne besede: piezo elektri~nost, poliviniliden fluorid, piezokompozit, s steklenimi vlakni oja~an polimer, metoda kon~nih
elementov, programsko orodje ANSYS
®
1 INTRODUCTION
During recent decades there has been an increasing
interest in smart materials. The benefits of smart piezo-
electric materials
1
include sensing, actuation, structural
health monitoring, smart structures and energy-harvest-
ing applications. The piezoelectric energy harvester has
become more popular in a wide variety of applications.
Micro-energy can be harvested from the natural re-
sources i.e., mechanical vibration, mechanical stress and
strain, thermal energy sources, solar energy, chemical en-
ergy sources, etc. Researchers have pointed out that the
bidirectional woven glass-fabric-reinforced composites
are pertinent to smart composite applications. VARIP is a
better technique for the manufacture of composite struc-
tures with negligible voids and good strength. By vary-
ing the frequency response, the maximum voltage could
be attained and thereby a suitable way of positioning the
piezoelectric material also on the glass-fiber-reinforced
polymer could be identified. Finite-element modelling
Materiali in tehnologije / Materials and technology 58 (2024) 6, 783–791 783
UDK 544.022.346:537.226.86 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek Mater. Tehnol.
*Corresponding author's e-mail:
jeroldresearch@gmail.com (Jerold John Britto J.)

and analysis are essential for the development of
piezo-enabled composites.
Heywang et al. have addressed the experimental in-
vestigation on the direct and inverse piezoelectric ef-
fects.
2
Vatanserver et al. investigated the voltage re-
sponse and the mechanical stimulus of PVDF in various
temperature for the purpose of identifying the suitable
type of PVDF material viz. LDT1-028K, LDT2-028K,
LDT4-028K.
3
Vasanthanathan et al. developed a fi-
nite-element model of a non-circular shaft using
ANSYS
®
with the smart finite-element modelling of
piezo zirconate titanate embedded glass-fiber-reinforced
polymer
4,5
cantilever beam under free and forced vibra-
tions. Vinod et al. proposed the effect of positioning the
piezo-fiber composite (PFC-W14) that is embedded
along the multilayer glass-fiber-reinforced composites.
6
Lee et al. developed a piezoelectric harvester
7
that
was mounted inside the tire for implementing wireless
sensor technology wherein the energy harvester technol-
ogy transmits the residual energy from the environment
and converts it into the electrical energy to observe the
performance of the tire. The observation has been made
by fixing the strain gauge (Y11-FA) by which the signal
has been transmitted from the transducer which could
consume the energy of 1.9 mJ every 8.3 s with a velocity
of 60 km/h by applying the capacitor of 2000 μF. Viet et
al. have suggested a model of floating mass spring-pi-
ezoelectric energy harvester
8
in order to extract energy
from the intermediate and deep energy harvester. The
mass spring system presented by Viet et al. observed the
wave motion and converted it into the mechanical vibra-
tion that would lead the piezoelectric lever devices,
which in turn could generate the electric power. Viet et
al. have also found that the harvested electric source ob-
tained was 103 W from the floating waves by varying the
width, height, length and mass of the system. Chang et
al. showed the enhancement of pyroelectric coefficient of
lead zirconate titanate
9
and stainless-steel laminated
composite for increasing the maximum power density.
Broadhurst et al. described the molecular and bulk struc-
ture of PVDF
10
which is crystallized and melt into
spherulitic structures of thickness 10–20 mm. Hwang
studied the piezoelectric response
11
of unidirectional
glass-fiber-epoxy composite. Kimi et al. investigated the
mechanical property and failure mechanism of glass-fi-
ber-reinforced polymer made by both hand lay-up and
vacuum infusion
12
technique.
The study in the present paper deals with two phases
of work:
• In the first phase of the paper, a finite-element model-
ling of smart piezo-composite has been carried out
using commercially available ANSYS
®
Mechanical
APDL software. In the finite-element simulation,
PVDF was embedded along with the GFRP laminate
by providing necessary boundary conditions. The
simulation results were observed for parameters, i.e.,
varying frequency, voltage and providing the har-
monic response. This phase also deals with the me-
chanical characterization of GFRP material fabri-
cated through VARIP in accordance with ASTM. The
experimentally observed mechanical properties of
GFRP were incorporated into the FE model.
• In the second phase of the paper, the experimental
setup which accommodates GFRP cantilever piezo-
composite, DC motor to induce forced vibration and
a microcontroller was developed to experiment on the
response of piezocomposite beam under forced vibra-
tion.
2 MATERIALS AND METHODS
2.1 Materials
2.1.1 Piezoelectric material
The present study emphasizes LDT0-028K, which is
a stretchy PVDF polymer with printed Ag inkjet elec-
trodes. The LDT0-028K is a piezoelectric sensor de-
signed to convert mechanical vibrations or pressure
changes into electrical signals commonly used for sens-
ing, measuring and monitoring physical phenomena
manufactured by Measurement Specialties, Inc.
(MEAS), which is now a part of TE Connectivity. The
sensor was designed compact and lightweight, with high
sensitivity to detect even small changes in pressure, ac-
celeration or force. The selection of LDT0-028K aligns
with its specific functional properties, such as piezoelec-
tric strain and stress coefficients.
Table 1: Material properties of PVDF
13
Properties PVDF
Young’s Modulus (E) 2e9 GPa
Poisson’s ratio (Y) 0.29
Piezoelectric strain coefficient (d
31
) 22e-12 m/V
Piezoelectric stress coefficient (g
31
) 216e-3 Vm/N
Density ( ) 1.78e3 kg/m
3
Permittivity constant ( ) 106e-12 F/m
Permittivity constant ( / o
)1 2
J. J. BRITTO et al.: SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED COMPOSITE STRUCTURE ...
784 Materiali in tehnologije / Materials and technology 58 (2024) 6, 783–791
Figure 1: Polyvinylidene fluoride (LDT0-028K) sensor

LDT0-028K is fitted into two crimped contacts hav-
ing the dimensions (25 × 13) mm, as shown in Figure 1.
The PVDF features both piezoelectric and ferroelectric
characteristics. The PVDF used in the present investiga-
tion was supplied by spark fun electronics (Pvt.) Ltd.,
US, and the properties of PVDF are represented in Ta-
ble 1.
2.1.2 Composite materials
The reinforced material used in the study was glass
woven fabric and the matrix medium selected was epoxy
(LY556) with a compatible hardener (HY951). The mix-
ing ratio of epoxy to hardener was 1:10, as per the meth-
odology outlined in the fabrication process. The glass
fabric was supplied by Urja products (Pvt.) Ltd.
Ahmedabad and the epoxy resin with hardener was sup-
plied by Huntsman Advance Materials, Switzerland. The
preference for GFRP is that GFRP is commonly used in
massive structures where structural health monitoring;
micro energy harvesting can be implemented. GFRP is
driven by its lightweight nature, high strength-to-weight
ratio, corrosion resistance, durability, design flexibility,
and other properties that collectively contribute to the ef-
ficient construction, reduced maintenance, and long-term
structural integrity. The physical properties of the fabric
and matrix are shown in Table 2 and Table 3 respec-
tively.
2.1.3 Structural geometry
For performing the experimental and finite-element
investigation, a piezo-enabled GFRP beam structure of
size (300 × 28 × 1.03) mm was modelled, as represented
in Figure 2. The PVDF of size (14 × 25) mm with thick-
ness as 25 μm is bonded at a distance of 28 mm from the
left. The structural geometry of the piezo-enabled GFRP
beam structure was modelled using Solidworks
®
2013.
J. J. BRITTO et al.: SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED COMPOSITE STRUCTURE ...
Materiali in tehnologije / Materials and technology 58 (2024) 6, 783–791 785
Figure 3: Laminate preparation using vacuum-assisted infusion technique
Figure 2: Structural geometry of piezo-enabled GFRP beam structure
Table 2: Physical properties of Glass fabric
14
Weave type
Fabric width
mm
Count (Along
wrap & weft)
Filament diameter
(μm)
Thickness
(mm)
Weight per
sq.meter. (g/m
2
)
Tensile strength
MPa
Plain 1000 3k 11 0.27 380 115/warp
Table 3: Physical properties of Matrix
15,16
Matrix Type Curing Temperature Flash point
Density
(kg/m
3
)
Tensile strength
(MPa)
Epoxy Araldite (LY556) 20 °C – 180 °C – 1.06 e
3
33
Hardener Aradur (HY951) – 110 °C 1 e
3
–

2.2 Fabrication of composite laminate
2.2.1 Vacuum-assisted resin infusion process
VARIP was used for the fabrication of the GFRP test
coupons and the GFRP beam structure. VARIP is one of
the advanced technique under close mould process for
the fabricaiton of polymer matric composites (PMC),
which uses the resin infusion-technique. VARIP provides
larger ua ltimate strength, tensile modulus, shear
strength, negilible void content while comparing with
other fabricaiton techniques. VARIP
17,18
was designed to
create void-free composite structures.
The vacuum pressure applied during the resin-infu-
sion process helps remove air and other gases from the
mold, minimizing the likelihood of voids in the final
product. This is particularly important for applications
where structural integrity and performance are critical.
The glass fabric/epoxy laminate was prepared by using
VARIP, as shown in Figure 3, to provide better strength.
Initially, the polymer base plate is cleaned with acetone
to remove the dust particles. A thin wax film was coated
over the entire polymer base plate so as to remove the
fabricated part easily. The glass fabric layer having ori-
entation of 0°/90° is placed over the thin wax-coated
polymer base plate. A green mesh mat was placed over
the fabric, which would provide the uniform distribution
of resin flow over the entire surface of the glass fabric
and a peel ply was kept in between the glass fabric and
green mesh mat to provide for easy removal of the fabri-
cated glass fabric/epoxy laminate. The spiral warp was
fixed at the one end of the setup for the purpose of suc-
tion. The whole setup was covered by breather cloth or
vacuum bag (0.05-mm thick) and the bag was sealed us-
ing sealant tapes (AT90 AT140; 12 × 3 mm) so that the
whole setup would be subject to vacuum. The end of the
setup was connected to the vacuum pump (Model: F182,
speed 1440 min
–1
, 2.4 amp, 230 V, 50 Hz, 1 HP) through
the catch pot. The catch pot plays a significant role in
pressure control and also the excess resin would be col-
lected in the catch pot. When the vacuum pump is
switched on, suction was induced. At another end of the
setup, the resin and hardener mixture of ratio 100:27 was
taken in a container. The epoxy resin along with the
hardener was drawn and it spreads uniformly over the
glass fabric. Finally, the curing was carried out in vac-
uum at room temperature. Test specimens as per ASTM
dimensions were cut from the composite laminate made
and subjected to material testing.
2.3 Material characterization
The principal objective of the present material char-
acterization is to extract the material properties of the
glass-fabric-reinforced composite. The experimentally
obtained material properties of GFRP are given input to
the finite-element analysis procedure. The finite-element
method (FEM) simulations rely on accurate material
property data as the input. Material characterization pro-
vides essential information such as elastic modulus,
Poisson’s ratio and other material constants needed for
the simulation. The information is crucial for defining
the material behaviour within the FEM model under dif-
ferent types of forces or pressures applied. In the present
experimental work, the material characterization of the
GFRP was obtained in accordance to ASTM using a FIE
make UTE-40 Universal Testing Machine.
The displacements were measured using an elec-
tronic extensometer of 50 mm standard gauge length.
The uniaxial tensile testing was conducted and the unidi-
rectional mechanical properties, i.e., Young’s modulus,
J. J. BRITTO et al.: SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED COMPOSITE STRUCTURE ...
786 Materiali in tehnologije / Materials and technology 58 (2024) 6, 783–791
Figure 4: GFRP Test coupons after mechanical testing
Table 4: Test-coupon configuration
ASTM Range of thickness (mm) Quantity Details
D3039 1.32 - 1.33 5 Tensile test to obtain Young’s Modulus
D3518 1.33 - 1.29 5 Shear test to obtain Shear modulus

tensile strength, shear strength and shear modulus were
experimentally estimated. Figure 4 shows the tensile test
coupon and the shear test coupons and Table 4 shows the
test-coupon configuration of GFRP for performing mate-
rial characterization.
The load vs displacement plot for all the test coupon
was extracted from the universal testing machine. The
experimental results for the tensile (ASTM D3039) and
the shear (ASTM D3518) were plotted, and it was noted
that the load bearing capacity varies in the range of 9 kN
to 10.6 kN. Similarly, for the shear test coupons, the
load-bearing capacity varies in the range of 10.1kN to
14.4 kN.
The material characterizations of all the specimens
are listed in Table 5. F
m
is the maximum force withstand
by the test coupon whereas the displacement at F
m
shows
that displacement value about the total length of the test
coupon from both the ends of the grippers.
2.4. Finite-element method
The FEM can solve the complex material models
with complex loading environment and boundary condi-
tions. The FEM for piezo-enabled composite structures
involves simulating the behaviour of materials and struc-
tures that incorporate piezoelectric elements. Piezoelec-
tric materials generate an electrical charge in response to
the mechanical stress The present analysis is predicted as
a coupled field analysis that couples the structural proce-
dure along with the electrical effects. The entire finite-el-
ement analysis was carried out using an ANSYS
®
16.0
Mechanical APDL.
2.4.1 Piezoelectric constitutive relation
The piezoelectric constitutive relation
19,20
was incor-
porated into the finite-element formulation. Piezo-en-
abled composite structures involve coupled fields, where
the mechanical and electrical responses are interrelated.
FEM models need to account for this coupling to accu-
rately predict the behaviour of the structure. Piezoelec-
tric materials act as an interaction between the electrical
and mechanical behaviour of the material. The mathe-
matical modelling of the piezoelectricity is shown in the
Eqn (1)
{}[] {}[] {} TCSeE =− (1)
{}[]{}[] {} DeSdE =+
T
(2)
2.4.2 Finite-element modelling of piezo-enabled GFRP
composite
Finite-element modelling of piezo-enabled GFRP
beam structure was carried out using the software
ANSYS
®
Mechanical APDL. Karthik Vinayaga et al. and
Jerold John Britto et al. studied and simulated the fi-
nite-element model of composite materials embedded
with piezoelectric structures.
21,22
A smart cantilever con-
figuration has been proposed, which comprises a host
structure and sensor in which the host structure is made
up of glass-fabric-reinforced composite and the sensor is
made up of polyvinylidene fluoride. Harmonic analysis
is useful for studying the steady-state response of the
structure under harmonic excitation, while transient anal-
ysis is suitable for capturing dynamic responses to
time-varying inputs.
Table 6: Finite-element modelling details
Software Package used ANSYS 16.0 Mechanical APDL
Analysis Type
Harmonic analysis
(Structural-electric)
Mesh size (Element
edge length)
1mm
Material GFRP PVDF
Element Type Solid 185 Solid 5
Material model Orthotropic Isotropic
Maximum number of
nodes
20992 780
Maximum number of
elements
10200 350
Boundary conditions
and Loading
One end of the beam:
Ux
, U
y
, U
z
=0
Another end (Tip) of the beam:
Fy
= –0.196133 N
Two sides of the beam:
Ux, Uz
=0
J. J. BRITTO et al.: SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED COMPOSITE STRUCTURE ...
Materiali in tehnologije / Materials and technology 58 (2024) 6, 783–791 787
Table 5: GFRP Material characterization results
Sl.
No.
ASTM
F
m
(kN)
Displacement at
F
m(mm)
Elongation
%
Young’s Modulus
(MPa)
Load at break
(kN)
1.
D3039
9.52 8.7 9 37850 9.52
2. 8.94 8.6 9.1 37594 9.1
3. 8.94 10.5 10.6 39407 10.6
4. 9.30 10 10.1 37537 10.1
5. 9.17 9.4 9.7 38097 9.83
Sl.
No.
ASTM
Fm
kN
Displacement at
F
m
(mm)
Elongation
%
Shear Modulus
(MPa)
Load at break
(kN)
1.
D3518
2.84 6.7 10.1 2654 0.92
2. 2.42 8.2 11.4 2819 0.95
3. 2.92 12.5 14.4 3768 1.20
4. 2.73 9.13 11.97 3080 1.02
5. 2.56 7.86 13.3 3657 1.15

The assumptions considered for the analysis are
shown in the Table 6. Solid 5 is the three-dimensional
coupled solid having 8 nodes with 6 degrees of freedom
such as U
x
, U
y
, U
z
, Volt, Temp & Mag at each node.
SOLID5 has a three-dimensional magnetic, thermal,
electric, piezoelectric, and structural field capability with
limited coupling between the fields. The element has
eight nodes with up to six degrees of freedom at each
node. Solid 185 is the layered structural solid element
that includes layer thickness, number of plies and mate-
rial orientation. SOLID185 is a three-dimensional,
20-node, higher-order hexahedral element. It supports
eight nodes at the corners and additional mid-side nodes
to improve the solution accuracy. In solid 185 degrees of
freedom is represented as U
x
, U
y
and U
z
. Both the solid 5
and solid 185 have been chosen for the modelling of
polyvinylidene fluoride and glass-fabric-reinforced com-
posite in the present analysis. The meshing view of the
sensor and host structure and the finite-element model
are shown in Figure 5 respectively. The finite-element
assumptions have been made on the basis of the experi-
mental arrangements.
To consider the vibration along the mode 1 (bend-
ing), one end of the beam was fixed by arresting all the
degrees of freedom and the load acting on the tip of the
beam is considered as the weight of the DC motor,
PVDF sensor and the tape attachments were assumed to
be approximately 20 g, which in turn converted into an
equivalent load of 0.196133 N. The vibration produced
in the experimental setup was forced vibration, which in-
duces under the harmonic response. For considering the
mode 1 response, the two sides of the cantilever beam
considering the degrees of freedom U
x
, U
z
were fixed and
providing the movement only along U
y
direction. To pro-
vide the forced vibration to the - enabled composite
beam, a harmonic analysis was enabled.
2.5 Experiment
The experimental setup consists of a glass-fabric-re-
inforced polymer laminate that would act as cantilever
beam and a PVDF sensor that is patched on the cantile-
ver beam at a distance of 28 mm from the free end. A
5-V DC motor of 1000 rpm is fixed at the free end of the
cantilever beam for producing the required vibrations.
The glass-fabric-reinforced polymer beam was fixed in
the aluminium stand. A schematic diagram of the
piezo-enabled GFRP beam setup is shown in the Figure
6(a). The DC motor is being connected to the step-down
transformer along with the rectifier and filter. The
J. J. BRITTO et al.: SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED COMPOSITE STRUCTURE ...
788 Materiali in tehnologije / Materials and technology 58 (2024) 6, 783–791
Figure 6: a) Schematic diagram of smart piezo-enabled GFRP beam, b) Experimental arrangement
Figure 5: Meshed model and the applied boundary conditions

step-down transformer is used to convert the high voltage
input into the low voltage output. After reducing the
noise level using the filter, the rectifier will convert the
AC power to DC power and the regulator synchronize
the required voltage to the DC motor. The motor was
completely fixed at the tip of the GFRP beam. Then the
beam starts to vibrate as a result of motor rotation.
The terminal point of PVDF sensor is fixed with the
PIC16F877A microcontroller which has the total number
of 40 pins out of which 33 pins are used as an input and
output and the respective coding was dumped into the
microcontroller. A liquid crystal display is connected
along with the microcontroller to display the generated
voltage and frequency. The experimental setup of
piezo-enabled GFRP is shown in the Figure 6b When
the motor rotates continuously, the glass-fibre-reinforced
epoxy composite beam could vibrate. The forced vibra-
tion of the piezo-enabled beam leads to the mechanical
straining of the beam which in turn generates voltage us-
ing PVDF. The generated voltage has been recorded
from the different frequencies. While repeating the cycle
during a certain point, it is noted that a constant voltage
has been obtained at certain frequencies.
3 RESULTS AND DISCUSSION
The uni-directional elastic properties, i.e., Young’s
modulus, shear modulus and the strength parameters,
i.e., tensile strength, shear strength of GFRP material,
were experimentally estimated. The qualitative analysis
of the fractured surfaces of the glass-fabric/epoxy com-
posite under uni-axial tensile, shear and forced vibration
was also conducted. The fractured surfaces of a glass-
fabric/epoxy composite observed after a material testing
provided valuable insights into the material’s failure
mechanisms, behaviour under loading and the overall in-
tegrity of the composite structure. The features observed
on fractured surfaces indicated of the mode of failure and
helped analyse response of material under applied stress.
Observation of broken fibres suggested that the compos-
ite has reached a point where the fibres themselves have
fractured. Cracks in the epoxy matrix were visible, indi-
cating the initiation and propagation of fractures within
the matrix. The extent and pattern of matrix cracking
provided insights into the composite’s overall toughness.
In harmonic analysis, structures are subjected to har-
monic loading, and the material response can vary with
frequency. Material characterization provided data on
how the GFRP responded under harmonic excitation, al-
lowing for the accurate representation of frequency-de-
pendent material properties in the FEM model. Har-
monic analysis identified the resonant frequencies at
which the structure tends to vibrate with maximum am-
plitudes. Material characterization aided in understand-
ing how the GFRP structures respond to different reso-
nant frequencies and helps tp predict mode shapes,
which represent the spatial distribution of vibration. It
was found that the commercial FEM software package
ANSYS
®
was compatible for the simulation of smart
PVDF-enabled glass-fabric-reinforced beam structure
under forced vibration. GFRP composite incorporated
with piezoelectric elements, material characterization
was crucial for understanding their behaviour under har-
monic loading. Piezoelectric materials generated electri-
cal charges in response to mechanical stress. Figure 7
shows the voltage generation plot of PVDF embedded
J. J. BRITTO et al.: SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED COMPOSITE STRUCTURE ...
Materiali in tehnologije / Materials and technology 58 (2024) 6, 783–791 789
Figure 7: Simulation results: voltage generated for varied frequency input

GFRP beam at different frequencies for the ranges
16 Hz, 19 Hz, 22 Hz, 25 Hz and 34 Hz using ANSYS
®
.
The voltage range was predicted under the harmonic re-
sponse using Finite-element capabilities. A simple, cost-
effective, smart piezo-enabled GFRP cantilever beam
structure was developed for micro-energy harvesting. It
was observed from experiments that for a 5-V DC motor,
a maximum voltage of 43 mV at a frequency of 34 Hz
was obtained, while FEM predicted a maximum voltage
as 45.59 mV for the same frequency. It was seen an aver-
age of 6.2 % error while comparing the experimental and
FEM results. Experimental validation helped confirm
that the FEM model accurately represented the real be-
haviour of the structure. It verified that the assumptions,
material properties and boundary conditions applied for
the simulation aligned well with the physical system.
The results shown in the present study would be useful
in energy harvesting structure design applications. The
present study also gave an ample suggestion for carrying
out experiments and finite-element simulation for har-
monic response of piezo-composites.
The finite-element results are in good agreement with
the experimental results. The voltage response based on
the constant voltage generation for the frequency viz.
16 Hz, 19 Hz, 22 Hz, 25 Hz, and 34 Hz is plotted in Fig-
ure 8. While comparing with the finite-element results,
the error in the experimental results may be due to the
uncertainties and also because of the presence of changes
in external atmospheric factors such as intention of pres-
sure, temperature etc. This may cause interrupt to the
real time vibrational environment. Numerical simulation
suggests that any ANSYS
®
composites and structural
modules can be used for positioning and arranging the
sensors over large-scale structures such as aerospace, au-
tomotive and civil engineering. However, challenges re-
main in scaling this technology for larger systems, as the
complexity of integrating piezoelectric sensors into more
extensive structures might require more advanced fabri-
cation methods. Additionally, environmental factors,
such as temperature and external vibrations, could affect
the performance of the piezo-composite structures in
real-world applications.
4 CONCLUSION
A simple fabrication technique using vacuum bag-
ging method for the fabrication of void free GFRP lami-
nates was presented in this paper with an emphasis on
development of a smart piezo-enabled GFRP beam.
The study showed that GFRP composites embedded
with PVDF sensors have applications in structural health
monitoring and energy harvesting, achieving a maximum
experimental voltage of 43 mV at 34 Hz.
The finite-element modelling using ANSYS® pro-
vided a maximum predicted voltage of 45.59 mV, with
an error of 6.2 % compared to the experimental results.
The GFRP specimens exhibited Young’s modulus of
up to 39,407 MPa, indicating high material stiffness,
while tensile strength reached up to 10.6 kN.
The piezoelectric characteristics of the composites al-
lowed for micro-energy harvesting, demonstrating the
material’s practical utility in smart structures.
Disclosure statement
The authors declare that they have no relevant or ma-
terial financial interests that relate to the research de-
scribed in this paper.
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Nomenclature
{T} Stress vector
[C] Elasticity matrix
{S} Strain vector
[e] Piezoelectric matrix
{E} Electric field vector
{D} Electric field vector
[d] Dielectric matrix
E Young’s modulus, GPa
 Poisson’s ratio
d
31
Piezoelectric strain coefficient (m/V)
g
31
Piezoelectric stress constant (Vm/N)
 Density, kg/m
3
 Permittivity constant, (F/m)
 / 0
Relative permittivity
GFRP Glass-fibre-reinforced polymer
PVDF Polyvinylidene fluoride
ASTMAmerican Standard for Testing Materials
FEM Finite-element method
PMC Polymer-matrix composite
F
m
Maximum force withstood by the test coupon, kN
J. J. BRITTO et al.: SMART PIEZO-ENABLED GLASS-FABRIC-REINFORCED COMPOSITE STRUCTURE ...
Materiali in tehnologije / Materials and technology 58 (2024) 6, 783–791 791