drs. sameer b. mulani & samit roy, the university of ... · 1 intelligent self -healing...

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Intelligent Self-Healing Composite Structure Using Predictive Self- Healing and Dynamic Data-Driven Application System (DDDAS)

Drs. Sameer B. Mulani & Samit Roy, The University of Alabama, Tuscaloosa, USA

• Summary of Effort– To develop a crack detection and healing system that is capable of automated

repeatable healing using Macro-Fiber Composite with DDDAS

• Key Focus of Scientific Research– Damage Prognosis, Damage Sensing, Automated Self-Healing

• Accomplishments– Task 1: Fabrication of composite laminates with non-autonomous mendable

polymer and perform Double Cantilever Beam (DCB) tests

– Task 2: Development of a basic damage prognosis model (e.g. modelingdelamination of a composite laminate using cohesive zone failure model)

– Task 3: Predictive Self-Healing actuation using sensors

• Other performers on project

– PIs: Dr. Sameer B. Mulani; Dr. Samit Roy

– Students: Bodiuzzaman Jony; Mishal Thapa; Nilesh Vishe

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• Introduction

Why Intelligent Self-Healing Composite Structure UsingPredictive Self-Healing and Dynamic Data-DrivenApplication System? Composites Structures are widely used due to high stiffness and

strength to weight ratio, durability, and design flexibility among others

Detection, repair and replacement process of damage takes a lengthydowntime and high maintenance cost

There is a need for dynamic data driven mathematical models to predictthe damage and activate Self-Healing process cost effective

Ability of a material to heal (recover/repair) it’s crack by itself is knownas Self-Healing

A bio-mimetic process known as Close Then Heal (CTH) that follows twostages: 1). Close 2). Heal; similar to human skin


Dr. Sameer B. Mulani & Samit Roy, The University of Alabama, Tuscaloosa, USA

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• Research GoalDamage Sensing Module: uses Macro Fiber Composite (MFC) network

Damage Prognosis Module: Cohesive Zone Modelling (CZM), Kalman Filter

Self-Healing Module: Ifcritical damage state is detected/predicted by the first two modules, the healing mechanism is activated by high voltage ultrasonic excitation of local MFCs



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• Results: (Task1 and Task 3) Conventional Healing Load vs. Cross-head displacement data obtained from the Q-Test

Machine were used to calculate the GIc

Load vs. displacements can be divided into linear and non-linear region Linear region for propagation of crack along the pre-crack region Near to the peak load, the deviation from linearity occurs. This is the point

where onset of new crack growth and propagation takes place The stick-slip pattern in non-linear region represents transition between

ductile and brittle crack growth

a) Pristine b) First Heal



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Increasing pattern in load due to the ductile nature of thermoplastic healants

Different trends in the non-linear region suggests the crack propagation along different path in the mid-layer.

This suggests different fracture energy required for crack propagation even though the specimens are obtained from same laminate

Healing Efficiency for first heal cycle was 73.33 % and 58.20 % for seventh heal

The coefficient of variation was less than 7 % for four specimens during all heal cycles

Decrease in healing efficiency observed with repeated fracture and healing. This is due to the thermal degradation of the healants

c) Third Heal d) Seventh Heal

• Results: (Task1 and Task 3) Conventional Healing



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Fig. (a) and Fig. (b) depicts the healant as well as the SMP which is responsible for bringing the cracked surface closer.

The smooth surface in Fig. (c) suggests interfacial debonding of fibers and thermoplastic adhesives, while the rough area shows the crack propagation through the matrix

Fig. (d) represents the crack deviation from the one surface from another surface after the first heal

Plastic flow of healants in Fig. (e) suggests high resistance of healants for crack growth

b). SMP ligament separation

a). Virgin fractured surface

Breaking of SMP bridging

d). Deviation of crack path after the first heal

c). Fracture surface after first

heal

Rough region

e). Near pre-crack end

• Results: Field Emission Scanning Electron Microscope (SEM) Images

Intelligent Self-Healing Composite Structure Using Predictive Self-Healing and Dynamic Data-Driven Application System (DDDAS)


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a). Virgin specimen

b). Delaminated specimen

c). Healed specimen

d). Bridging Ligaments (Fibrils)

The edge-view provided the evidence for healing visually with no marks of crack in the healed specimen

The thermoplastic fibrils or bridging ligaments was observed in the crack region

The fibrils offer extra resistance for opening and crack propagation by lowering the stress at the crack tip

• Results: Micrographs



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MFC utilized in our research to replace conventional healing in the oven as well as for sensing the crack

Conversion of the mechanical energy to electrical energy by piezoelectric effect as well as conversion of electrical energy to mechanical energy based on inverse piezoelectric effect

P1 type MFC used in our research which utilize the d33 effect and act as elongators

Macro-Fiber Composites MFCs attached on the top surface of the DCB

specimen

Flow diagram of MFC actuation

• Results: (Task 3) Macro-Fiber Composite (MFC) Actuated Healing



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Time required for MFCs to reach 80 oC under different

operating (voltage and frequency) condition

Results for a representative specimen with MFC actuated healing at 80 oC for two hours

at 250 Volts and 4 kHz

The parametric study demonstrated the possibility of using low voltage to attain sufficient temperature for healing the fractured DCB specimens with less heating time

The FLIR camera and thermocouple was used to monitor the temperature to maintain 80 oC

At 30 seconds

At 300 seconds

Thermal imaging with FLIR camera for MFC actuated

healing




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Comparison of healing efficiencies with Conventional (Oven) and MFC healing

Conventional Healing MFC actuated healing at 100 Volts and 32 kHz


The specimens were also healed with MFC actuated heating at 200∼250 V and 4 kHz frequency for two hours. The temperature was maintained at 80 oC

Comparable efficiency with MFCs were obtained to that of specimens heated in oven at 80 oC for two hours

The parametric study of heating time were carried out for both conventional and MFC actuated system

The temperature of ∼ 80 oC was maintained for both studies

The results showed the possibility of achieving similar healing with less healing time



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Cohesive Zone Modeling uses special interface elements to model the delamination process in a finite element framework

The process zone acts as a transition form the traction free (cracked) and intact material region

CZM depends on the traction-separation law and depends on three step process: 1). Damage initiation, 2). Damage evolution, and 3). Element removal upon total failure

CZM for crack growth

Process Zone

Bi-linear model for CZM(Other models such as Exponential can

also be used)

CZM parameterswith tuning

K(lbf/in^3)

Values 4.836 1.049*1e6 1450.4

• Ongoing Progress, Task 2: Cohesive Zone Modeling (CZM) for Mode-I Interlaminar Fracture

The CZM parameters such as fracture energy (GIC), stiffness (K), and maximum traction (t0)are used based on the experience and are given Table below



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The FEA simulation for Cohesive Zone Modeling of DCB specimens (Cohesive elements were kept after

failure) in ABAQUS

Crack growth for Mode-I interlaminar fracture was model in ABAQUS for preliminary studies

The CZM will be performed in NOVA 3D FEA software once the CZM parameters are extracted using the experimental data

Load vs. displacement behavior obtained with DCB tests and FEA

simulations (CZM modeling)

• Ongoing Progress, Task 2: Cohesive Zone Modeling (CZM) of DCB specimens simulated in ABAQUS



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Currently, the cohesive material properties is being calculated based on Double Cantilever Beam (DCB) test using Digital Image Correlation (DIC) and J-Integral approach

The J-integral estimation is given as:

Similarly, the cohesive stress can be calculated based on the change in J-values and crack opening displacement

: Cohesive Stress

2PJbθ

=

P θ b

cohesive Jσδ∂

=∂

: Load : angle of rotation at the loading pin : width of the specimen

• Ongoing Progress, Task 2: Experimental Estimation of Cohesive Zone Modeling (CZM) Parameters using Digital Image Correlation (DIC)



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Before Crack Growth During crack growthThe tracking of distance between two points

for fibril separation with DIC

The line used to measure the angle of rotation near to the pin with DIC

Before Crack Growth During crack growth

Angle of rotation with time for fibril separation

Load vs time

J-integral vs. crack opening for the fibril

Note: These results needs to be improved




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MTS Landmark Servo Hydraulic Test System

Images Captured using Digital Image Correlation

(DIC)

• Ongoing Progress, Task 4: Fatigue Test for Mode-I Fracture Toughness and Self Healing Efficiency



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Self-healing capability and repeatability was studied using thermoplastic healants for both conventional (oven) healing and MFC actuated healing

The proposed self-healing mechanism follows two-step process of ‘Close then Heal’. SMP helps in narrowing the cracks and CAPA helps in adhesion of the crack surfaces

The maximum efficiency was approximately 150 % for first heal and approx. 100 % for subsequent heal demonstrating feasibility and repeatability of self-healing

SEM images and micrographs indicated the mechanisms for self-healing

Parametric study of heating time suggested the possibility of using 20mins. compared to 120 mins. used earlier

The optimum operating condition for the MFC (P1) heating was found to be 100 Volts and 32 kHz for Square wave signal

• Conclusions



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Parameter Estimation for Cohesive Zone Modeling experimentally using J-Integral Approach

Development of a cohesive zone based Composite model using stochastic approach for dynamic data driven damage modeling

Investigating the healing performance under fatigue loading

Development of damage sensing system using MFCs as sensors and predictive healing with the same MFCs

• Future Work



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Conference Papers[1] J. Bodiuzzaman, M. Thapa, S. B. Mulani, and S. Roy, Self-Healing Repeatability of Thermoplastic Healant in Fiber Reinforced Thermoset Composite, in ASC 33rd Annual Technical Conference , Seattle, September 24-26, 2018.[2] M. Thapa, J. Bodiuzzaman, S. B. Mulani, and S. Roy, Experimental Characterization of Shape Memory Polymer Enhanced Thermoplastic Self-Healing Carbon/Epoxy Composites , in 2019 AIAA SciTech, San Diego, California, Jan 7-11, 2018.

Journal Papers[1] B. Jony, M. Thapa, S. B. Mulani, and S. Roy, Repeatable Self-Healing of Thermosetting Fiber Reinforced Polymer Composites with Thermoplastic Healant, Smart Materials and Structures (Under Review)[2] B. Jony, M. Thapa, S. B. Mulani, and S. Roy, Macro-Fiber Composite (MFC) Actuated Repeatable In-situ Healing of Micro and Macro Cracks in FRP Composites (Manuscript Under Preparation)

Book Chapter[1]. M. Thapa, B. Jony, S. B. Mulani, and S. Roy, Intelligent Self-Healing Composite Structure Using Predictive Self-Healing and Dynamic Data-Driven Application System, Springer. (Accepted for Publication)

• Publications



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This work was carried out under the grant FA9550-17-1-0033. Wewould like thank Erik Blasch (DDDAS Program Officer, AFOSR),the AFOSR and also the Department of Aerospace Engineeringand Mechanics at The University of Alabama, Tuscaloosa for theirkind support

• Acknowledgements



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a) SMPs in the mid-layer c) Laminateb) Compression Molding

e) DCB test samplesd) Table Saw

MTS Q-Test/5 Universal Testing Machine

DCB test specimen placed on the Testing

Machine (ASTM D5528)

• Fabrication of DCB test Specimen



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• Healing Methodology

Figure: Healing Cycle

The conventional (oven) healing of the fractured specimens has been successfully replaced with the MFC actuated healing



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Specimen 1 Specimen 2 Specimen 3 Specimen 4

MFC actuated healing at 100 Volts and 24 kHz approximately for 30 minutes

Similar trends as observed with conventional (oven) healing was also observed for MFC actuated healing

The load vs. crosshead displacement demonstrated the healing ability with less heating time compared to 2 hours utilized earlier

It also demonstrated the healing repeatability for a number of cycles




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R-curve for different healing cyclesCritical Fracture Toughness for

MFC actuated healing

Healing Efficiencies for MFC actuated healing


The MFC actuated healing demonstrated fracture toughness retention and healing efficiencies

The non-monotonic pattern in the healing results is due to the difficulty in maintaining 80 oC without actually burning the MFCs

This requires automated feedback control for MFC heating and is underway

The R-curve that plots fracture toughness at different crack lengths also demonstrated healing capability and repeatability

The different R-curves for different healing curves indicate crack growths along different paths in the mid-plane



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The traction-separation law for CZM :

Damage parameter for growing damage:

Experimental evaluation of is difficult, so using power law:

Critical displacement and maximum stress for damage initiation:

Critical fracture energy or toughness:

The material parameters for CZM need to be determined experimentally and dynamically characterized using the DDAS paradigm

Also, the material parameters are random and also the distribution of thermoplastic healants in the mid-layer have spatial variation

The UQ for damage analysis in interlaminar fracture will be carried out using: i) Polynomial Chaos Expansion, and ii) Karhunen-Loeve Expansion

[ ]*

1( ) 1 ( ) ( )o

tf cii t

i

T t t E t dt

δ δλα σ τ τλ δ δ

= − + − ∫

1

( )( )

Nk

kA A t

tA

α =

−=

∑

0 0 1m andα α λ λ α= ≥ ≤

0 0 1orα λ α= ≤ =

0 , , ,m Bα η

( ) ( ) ( )1/22 2 2* * *

00E

f

n r sσ δ δ δ ∆ = + +

2 2 2 2( ) ( )f Y S Y Bησ = + −

( )c Ic IIc IcG G G G Bη= + −

Experimental evaluation of is difficult, so using power law:

0 , , , , , ,fIC om B G Eα η σ

• Ongoing Progress, Task 2: Cohesive Zone Modeling (CZM) for FEA simulation of Interlaminar Fracture of DCB specimen



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Calibration for DICExperimental Set-up for DIC of DCB specimen

Crack Tip Fibrils Fibrils Separation

Tracking of Crack propagation and Fibrils Separation for DIC analysis

Note: DIC used to post-process the images captured during DCB test




drs. sameer b. mulani & samit roy, the university of ... · 1 intelligent self -healing...

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