A Report on

Short Course “FRP 2014”

FRP Composites: Overview, Characterization,

Analysis, Design and Applications

10th & 11th July 2014

at IIT Hyderabad

Hosted by

Department of Mechanical and Aerospace Engineering,

&

Department of Civil Engineering,

Indian Institute of Technology Hyderabad

1 | P a g e

Table of Contents

INTRODUCTION ................................................................................................................................. 2

SUMMERY OF DAY 1 ........................................................................................................................ 3

SUMMERY OF DAY 2 ........................................................................................................................ 4

DETAILS OF FRP COURSE .............................................................................................................. 5

Dr. Suriya Prakash‟s talk on „Overview of composites: Mechanical properties and applications‟ .... 5

Dr. Ramji‟s talk on „Manufacturing processes and compression behaviour of FRP composites‟ ...... 6

Dr. CM Majunatha‟s talk on „Mechanical testing of composites‟ ...................................................... 7

Mr.Kashafudoja‟s talk on „Experimental characterisation of FRPs and FEA modelling‟ .................. 8

Prof. P. Alagusundaramoorthy‟s talk on „FRP research at IIT Madras‟ ............................................. 9

Mr. Srinivas Aluri‟s talk on „Applications of FRP in bridges‟ ......................................................... 10

Dr. Viswanath‟s talk on „Mechanics and damage of FRP composites‟ ............................................ 11

Director‟s address ............................................................................................................................. 12

FEEDBACKS FROM PARTICIPANTS .......................................................................................... 13

2 | P a g e

INTRODUCTION

Fiber-reinforced polymer (FRP) composite are now being extensively used as primary and secondary

load bearing members in many industries like aerospace, automobile, civil infrastructure, wind

energy, marine and sports. The feature of custom tailored properties and heterogeneous nature offered

by composites call for special attention to their characterization. Testing of heterogeneous and

anisotropic FRP materials poses several challenges like numerous parameter identification,

development of specific test methodology and fixtures etc. As a whole, the knowledge of fabrication

methods, accurate machining and testing methodology is essential for researchers and practicing

engineers from design and manufacturing perspective.

Keeping in mind this purpose, IIT Hyderabad organized a short course on “FRP composites:

Overview, characterization, analysis, design and applications” on JULY 10th

-11th

, 2014 focusing on

following aspects:

1. Introduction to Composites

2. Manufacturing Processes

3. Basic Mechanics

4. Material Characterization

5. Whole-field Strain Analysis using Digital Image correlation (DIC) technique

6. Mechanics of Composite Repair

7. Fatigue life assessment

8. Applications and Case Studies

Invitations were sent to many engineering colleges and industries across India. Around 75 participants

attended this short course. Number of students also showed interest to attend the course along with

faculty members and industrialists. Speakers with expertise on FRP composites were invited from

academic and research organizations as well as from industries so that participant could get the

flavour of research and applications of FRP composites across the domain.

3 | P a g e

SUMMERY OF DAY 1

The day 1 began with the welcome speech by Prof. V. Eswaran, Head of Mechanical and Aerospace

Engineering. After that, there was a brief introduction about TEQIP program by Prof. N. Venkata

Reddy, Dean (R&D), TEQIP coordinator, IITH. He summarised various programs organised under

TEQIP program at IIT, Hyderabad. Thereafter, Dr. Suriya Prakash presented the overview of FRP

composites. He discussed about the applications of composites in modern day life. Following his talk,

Dr. M. Ramji gave the overview about various manufacturing processes used for preparing the

composite laminates and structures. Various materials used in composite structures were introduced in

this presentation. Later, Dr. C. M. Manjunatha discussed about the mechanical characterisation of

composites. In his talk, he presented various design philosophies used in design of composite

structures. Various tests mentioned in standards were introduced along with interpretation of results.

In the afternoon, Mr. Kashafudoja presented his work related to characterisation of composite

materials. He introduced participants with various ASTM standards used for testing. He presented

about Digital Image Correlation (DIC) and concluded his talk with results obtained for open cutout

CFRP panel. In the following session, he focussed on Finite Element Modelling of composites. He

gave a demo in ANSYS software using Graphical User Interface (GUI) as well as APDL codes. Then

all the participants visited the IITH central workshop to view various manufacturing and testing

facilities related to composites. This visit concluded the sessions of day 1.

Prof. V. Eswaran,

Head of Mechanical and

Aerospace Engineering

Prof. N. V. Reddy,

Dean (R&D) and TEQIP

coordinator

4 | P a g e

SUMMERY OF DAY 2

The second day program began with the talk by Dr. C. M. Manjunatha about the fatigue testing of

composites. He talked about various damage mechanisms in composites under fatigue loading.

Thereafter, he outlined the methods for fatigue testing, data collecting and post-processing of data.

Followed by him, Dr. M Ramji talked about compressive behaviour of composites. His talk focused

on the importance on behaviour of composites under compressive loading. He then presented various

compressive failure modes. Prof. Alagusundaramoorthy P. (Professor, IIT Madras) talked about FRP

research at IIT, Madras. Various applications of FRP‟s were discussed illustrated through various

projects done at IIT Madras. Thereafter, Mr. Srinivas Aluri (Hara industries) talked about the

applications of FRP‟s in bridge structures. Various applications in bridges were discussed along with

the dynamic response characteristics of FRP bridges. In the afternoon session, Sika India listed their

various products along with their advantages. Thereafter, the presentation by ATOS about Non

Destructive Testing was followed. The Infrared testing method was introduced. Dr. Viswanath

Chinthapentha presented about mechanics and damage in FRP composites focusing analytical aspects.

Finally, an interactive feedback session was conducted by Dr. M Ramji. After this session, all the

participants were awarded with the certificates for attending the course. This concluded the day 2 as

well as the overall FRP course.

5 | P a g e

DETAILS OF FRP COURSE

Dr. Suriya Prakash‟s talk on „Overview of composites: Mechanical properties

and applications‟

(10:00 AM to 11:00 AM, 10th July)

Dr. Suriya Prakash from IIT Hyderabad talked mainly about introducing the basics of composites.

Starting with the definition of Fiber Reinforced Polymers (FRPs), he listed various mechanical

properties that are needed for the analysis of composites. Thereafter, he presented on classifications of

composites. There are many types of composites eg. Particle reinforced, fiber reinforced, structural

laminates etc. Then the sizes of various types of reinforcements were compared. He briefly discussed

about the applications of FRPs in various fields along with advantages and challenges in their

practical application. Each constituent of FRP performs a different role. The matrix supports the fibes

and keeps them together while fibers are the main load taking members. He then talked about

properties of Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP).

Finally, the temperature effect on mechanical behavior of FRPs was discussed along with the effect of

fatigue loads.

6 | P a g e

Dr. Ramji‟s talk on „Manufacturing processes and compression behaviour of

FRP composites‟

(11:15 AM to 12:15 AM, 10th

July & 10:00 AM to 11:00 AM, 11th

July)

Dr. Ramji from Indian Institute of Technology, Hyderabad (IITH) discussed about the manufacturing

methods of composites. He talked about the mechanical properties of fibers and matrix materials.

Various manufacturing processes used for manufacturing glass fibers and carbon fibers were

discussed. The properties of continuous fiber, chopped fiber composites, pultruded sections were

compared. There are various methods for manufacturing composites like resin transfer process,

vacuum infusion process, hand layup process etc. Various factors that affect the properties of

composites were discussed.

On the second day, He discussed about behaviour of composite laminates under compressive loading.

At start he briefly discussed about various applications of composites in modern day world. Then he

told about the importance of compressive strength and damage analysis in composites. In

compression, local micro-buckling of fibers are the main failure unlike fiber breakage in tension.

There are various mechanisms by which FRPs fail in compressive loading. They are fiber

microbuckling, kinking, fiber crushing, splitting, buckle delamination.

Talk then followed the experimental procedure for compressive testing of composites. Special types

of fixtures were introduced to carry out the testing. SACMA and UCSB fixtures were used to carry

out tests. Then the results obtained from experiment and Digital Image Correlation (DIC) technique

were compared with the results obtained from Finite Element Analysis. Then the concept of

Progressive Failure Analysis (PFA) was introduced to understand the damage mechanics in

composites. Various cases of damage propagation were presented eg. Single hole in panel, two

interacting holes in panel etc. The talk was concluded with question and answers session.

7 | P a g e

Dr. CM Majunatha‟s talk on „Mechanical testing of composites‟

(12:15 AM to 01:15 PM, 10th

July & 09:30 AM to 10:00 AM, 11th

July)

Dr. CM Manjunatha is currently working as a Senior Principal Scientist and Group Head, Fatigue and

Structural Integrity Group, CSIR-NAL. He talked about mechanical characterization of composites.

He started with the discussion on three different design approaches: safe-life design, fail-safe design

and damage tolerant design. He emphasized on the building block approach for design of structures

which starts with coupon testing and stretches up to component testing. In aerospace industry, FRP

composites widely replace the conventional metallic alloys. There is need of testing of these

composites and characterize the same. ASTM has established many standards to conduct various tests

for composites. It includes tension, compression, shear, flexure, delamination, interlaminar shear, etc.

tests. ASTM along with many other organizations has designed various fixtures to conduct all these

tests. It is also required to get the behaviour of notch effect on the structures. The wing and fuselage

features come next to coupon testing. Also repaired composite panels are also tested at CSIR-NAL. It

is very critical to get the bearing strength of CFC (carbon fiber composite) joints. The next is

component level testing which includes wing-root fitting box test, wing test, fuselage test, etc. At the

end it comes to full scale fatigue testing of aircraft.

In spite of good design, structures often fail during service due to fatigue loading. Due to uncertainty

of failure of composites, the complete potential of FRPs is not used. The main fatigue damage

includes matrix cracking, fiber break and debonding, delaminations. It is very essential to design the

structures based on fatigue criterions and also to predict service life. Fatigue life prediction under

spectrum loads is very complex. Firstly it requires the cycle count data produced through rainflow

technique and also S-N curves. Then all data is transformed into one plot called Constant Life

Diagram (CLD) curve. It is used with various damage accumulation models to predict the life of the

structures.

The recent trend is to add nano size fillers in composites to improve the properties of FRPs. It is

called nanocomposites. Nano particle reinforced epoxy exhibit higher fatigue life over that of neat

epoxy. Same is observed in GFRP. So advanced nanocomposites appear to be potential futuristic

structural materials. There are very many interesting avenues for research in the areas of fracture

mechanics and fatigue.

8 | P a g e

Mr.Kashafudoja‟s talk on „Experimental characterisation of FRPs and FEA

modelling‟

(02:20 PM to 04:00 PM, 10th

July)

Mr. Mohammad Kashafudoja talked about the experimental characterisation of FRP‟s. He started with

applications of FRP‟s in various fields and the importance of characterisation. He talked about various

ASTM standards that are used for characterisation of FRPs. Various tests used for finding out

mechanical properties of CFRP panel were discussed. He explained the experimental procedure

followed during testing of CFRP panels. Then he discussed about the use of Digital Image Correlation

(DIC) technique in characterisation of CFRP. Then he compared the results obtained from MTS

machine with DIC results. Then he talked about repair of composites which is widely used in

aerospace industries. Single side and double side patch repair results were shown. He concluded his

talk by discussing about the progressive failure analysis.

The next session conducted by him focussed on Finite Element Modelling and Analysis of FRPs. He

demonstrated the step by step procedure to perform FEA in ANSYS software. He discussed about

both unidirectional and multidirectional composites. He demonstrated the procedure using the

graphical user interface (GUI) as well as APDL codes. Various commands used in APDL code were

discussed. This demo session was then concluded by discussing about loading process.

9 | P a g e

Prof. P. Alagusundaramoorthy‟s talk on „FRP research at IIT Madras‟

(11:15 AM to 12:15 PM, 11th

July)

Prof. Alagusundaramoorthy from IIT Madras discussed about the research towards FRP applications

done at structural engineering lab at IIT Madras. FRP deck panels have been tested at the lab. They

have inspected and evaluated bridge deck partially reinforced with GFRP rebars. Also the research

has been done on material selection and fabrication of FRP composite bridge deck panels. They have

used contact moulding hand lay-up process and also pultrusion for bridge deck panels. They studied

the fatigue of prototype GFRP composite bridge deck panels under enhanced fatigue loading. His

research group has done flexure tests on beams bonded with CFRP sheets and fabric. They have also

done experiments on shear strength of beams wrapped with CFRP fabric. They have facility to test the

columns having height upto 5 meters. The testing of segmentally erected composite girders has also

been done. Experiments on Seismic retrofit of column in beam-column joint using glass fiber fabric

are also carried out at the lab. The strength of stiffened composite plates with cutout under a

combination of axial and out of plane load is found experimentally. Research is going on strength of

steel and glass fiber reinforced composite plates with square opening under axial and out of plane

load. They have found the behaviour of GFRP retrofitted masonry assemblage under axial

compression and shear. They have established a novel setup for testing of ship deck stiffened panels

under axial and lateral loads.

10 | P a g e

Mr. Srinivas Aluri‟s talk on „Applications of FRP in bridges‟

(12:15 PM to 01:15 PM, 11th

July)

Mr. Srinivas Aluri from Hara Industries presented uses of FRP in bridges which includes retrofitting

of existing bridges, rebars with concrete and bridge decks/stringers. First generations of FRP bridge

deck was made of E-glass fabrics and Vinyl Ester resin. But it is very costly. Currently Prodeck 4 is

widely used bridge deck fabricated by pultrusion method. It is the third generation of FRP bridge

decks and its cost is reduced more than an half than its predecessor. Adhesive plays a major role in

transferring the load from one deck to another. Also spring clips are used to connect FRP deck

modules to girders. Its performance is evaluated using various static and dynamic testing. It is

required to check actual performance against design assumptions especially for new technologies such

as FRP. Through testing the parameters such as transverse load distribution factors, damping ratios,

natural frequencies, dynamic load allowance factor, vibration serviceability, etc. are determined. The

vibration of bridges due to moving traffic has potential problems like dynamic amplification of

stresses and vibration serviceability. The first one is accounted in design as DLA (impact factor)

while the second is not accounted in design. Dynamic Load Allowance (DLA) Factor is determined

by allowing a loaded truck to pass at 2 mph and at highway speeds. Ontario Highway Bridge Design

Code (OHBDC) chart provides an indication whether traffic-induced bridge vibrations are

perceptible. Damping usually not measured for steel-concrete & concrete bridges since inherent

damping of these bridges is sufficiently high enough to dissipate traffic induced vibrations. But

composite being lighter in weight has very poor damping properties. So Lack of inherent damping in

these bridges is the primary reason for high amplitudes of vibration. Research is currently underway

to improve damping in FRP decks using pour-in-place foams and lightweight granular materials.

11 | P a g e

Dr. Viswanath‟s talk on „Mechanics and damage of FRP composites‟

(02:30 PM to 03:00 PM, 11th

July)

Dr. Viswanath from IIT Hyderabad discussed about the basics of stress and strain. The constitutive

law relates the stress and strain through elasticity tensor. More the internal symmetries, the simpler

the structure of the elasticity tensor. Voigt notation is very handy to describe the constitutive law. It

transfers the stress/strain tensor into a vector form. The composite panels is nothing but a stack of

laminates having different fiber orientation. The classical laminate theory (CLT) makes it possible to

relate external loads (in-plane forces and moments) to the composite plate deformations. The ABBD

matrix is a result of this theory. Going further, it is required to establish model for damage mechanics.

Right now there are many damage models are available for composites. But no model is generic and

accurate. Composites have a huge hidden potential but it cannot be used until the damage in

composites can be predicted accurately. The damage mechanics in composites becomes complex due

to multiple failure modes. There are various failure theories like Tsai-Wu, Tsai-Hill, Hashin, Puck‟s,

etc. The Tsai-Wu quadratic interaction or tensor polynomial failure criterion (Tsai and Wu, 1971)

accounts for the interactive effects of a multi-axial stress state. s. The only region which it does not

work very well is for fiber compression failure, which is actually a geometrically driven failure and

not a true material property. For that type of failure, one of the “micro-buckling” types of criteria

seems to be more accurate.

12 | P a g e

Director‟s address

(02:15 PM to 02:30 PM, 11th

July)

Prof. U. B. Desai welcomed all the participants again on behalf of IIT-Hyderabad. He discussed about

active involvement of IIT Hyderabad in conducting different research and application oriented

programmes through TEQIP. There should be an interactive collaboration between educational

institute, research organizations and industries so that students and faculties can contribute to the

research, the major need of developing India and also this research should lead to some real and

feasible application so that society can also be benefited. He also talked about the current research

areas IIT Hyderabad working on. He appreciated the idea of organizers of conducting the course of

FRP composites which is nowadays widely used in aerospace along with other areas like marine,

automobile, etc. He requested all the participants to have a continuing interaction with IITH Faculty

and amongst themselves. He congratulated and encouraged them to participate in such activities.

Finally, he thanked Dr. Ramji and Dr. Suriya for organizing this course.

13 | P a g e

FEEDBACKS FROM PARTICIPANTS

The issue on environmental damages should be discussed

One session on secondary manufacturing processes such as cutting, machining, polishing, etc.

could be added.

Proper illumination level should be maintained in the lecture hall.

It could be good if the students got more time to interact with the experts to clarify their

queries.

The course should be stretched up to five days to include more topics and discussion.

The transportation facility was very good.

Many participants got the ideas and direction to begin and carry out their research further.

The characterization of composite should be discussed further in detail.

Group Photo in the Lecture Hall-3

Group Photo after visit to Workshop at IITH