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8/12/2019 Frp Construction

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ABSTRACT

The study and application of composite materials are a truly interdisciplinary endeavor that

has been enriched by contributions from chemistry, physics, materials science, mechanics and

manufacturing cnginecring. The understanding of the interface (or interphase) in composites isthe central point of this interdisciplinary effort.

From the early development of composite materials of various natures, the optimization of theinterface has been of major importance.

The central theme of this paper is tailoring the interface properties to optimize the mechanical

performance and structural integrity of composites with enhanced strength/stiffness and fracturetoughness (or specific fracture resistance). t deals mainly with interfaces in advanced

composites made from high performance fibers, such as glass, carbon, aramid, ultrahigh modulus

polyethylene and some inorganic

The paper contains discussions on microstructure!property, nature and definition of interfaces

in fiber reinforced composites, mechanical behaviour of fibre reinforced plastics, and

applications of fibre reinforced plastics in civil engineering

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1. INTRODUCTION

"omposite materials have been used since biblical times when chopped straw was added in

bric#s to ma#e building materials. The modern composite materials age began with the

introduction of particular fibrous reinforcement materials into thermosets phenollics in $%&&'s.

The first * was made in $%+. einforcement thermoplastic were virtually non!e-istent in

early $%&'s but by $%%&'s reinforcement thermoplastic represented about one fourth of the total

reinforced plastics composite materials.

0cientists have started mi-ing materials with different properties in new way so as to ma#e

new materials which have good properties of the constituent's materials without having the

inherent, wea#ness or disadvantages of the individual materials. These new materials are called

as composite materials. "omposite materials are made by the combining two or more than two

dissimilar materials. 1 selected fillers or reinforcing agents compatible matri- binder.(i.e.

esin) are combine in such a way that the resulting composite materials possess superior

properties which are not obtained with single constituent materials.

2ou may understand the nature of composite material by simply ta#ing e-ample of day to day

life such as concrete slab of our house. t is the most common composite material in our day to

day life. t consist of cement concrete and iron bars. The cement gives protection to the iron bars,

from adverse environmental condition iron bars gives the strength, fle-ibility stiffness to

structure. The idea and principle is e-actly applied in thermoplastic composites.

2. COMPOSITE MATERIALS "omposite materials are formed by the combination of two or more materials that retain their

respective characteristics when combined together to achieve properties that are superior to those

of individual constituents. n generic terms, the idea of a composite is analogous to that of

reinforced concrete. 3owever, composites present immense opportunities for tailoring of the

material to the specific re4uirements of the structure.

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3. CONSTITUENTS OF COMPOSITE MATERIALS

The composite materials are made up of constituent materials which are grouped as

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3.1. MATRIX: -

The main components of composites are reinforcing agents and matri-. The fibres,

particulates and whis#ers act as the reinforcement and provide most of the stiffness and strength.

The matri- binds the reinforcement together thus effecting the load transfer from matri- toreinforcement and adds to the performance merits of the material

Definition< The phases that receive the inserts in phase composition is continuous phase is

called as matri-. t is also called as binders. The matri- material employed for fabrication of

composites material are usually polymer commonly called as esin.

Funtion!< The function of matri- or binders are as follows.a) t gives mouldability or shape to composite.

b) t ma#es the composite materials generally resistance to adverse environment.

c) t also protects the reinforcement from adverse environments.

T"#e! -The materials used for the matri- are plastic, rubbers, ceramic metals. *lastic

matri- based composite materials now constitute more than %= of all composite materials in

use today. :oth Thermoplastic Thermosetting materials are used as matri- materials.

3.2. REINFORCEMENT: -

These are materials which basically give strength, stiffness other mechanical properties tocomposite materials. Fibres are the principle constituents in fibre reinforcement composite

materials.

Definition!: -t is materials which give strength, stiffness other mechanical properties to

composite materials.

Funtion: -The reinforcement are used to improve the structural characteristics of materials.

They can be continuous in form of fibre, filament or discontinuous in forms of (whis#ers, fla#e

or particular). The reinforcement increases the ratio of strength to density stiffness to density.

mprove formability electrical prop. t also increase resistance to corrosion fatigue, creep

raptures stress reduce cost.

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norganic or organic fibers such as carbon, glass, aramides etc have been widely used with

plastic mainly to improve mechanical strengths tensile modulus.

3.$. FIBER-MATRIX INTERP%ASE

The interphase between the fibre matri- can be easily identified> it is the behavior prop of

interphase that generally control the prop of the composite. The prop. of composite cannot

achieved by any of the components acting alone.

The main role of interphase is to transmit distribute stress on matri- to the fibres in desire

orientation.

;ocalised stresses are generally highest near the interphase which may be locus of premature

feature of composite. The interphase must have appropriate character in order to providenecessary load transfer from matri- to reinforcements.

3ence there should be strong adhesion forces between matri- fibre through interphase. This

can also be achieved by coupling agents.

"oupling agents are define as materials that improve the adhesion bonds of dissimilar

surfaces. "oupling agents modify the interphase region to strengthen the organic inorganic

boundary layers by a much positive attempt to increase the adhesion between polymer fibre

was lin# them by covalent bond using coupling agents. 7g < Titonates, 0ilanes.

3.&. FILLERS ' ADDITI(ES

Fillers should be inert their presence in a polymeric matri- should not affect the processing polymerization. Fillers are added is polymeric matri- for following reasons?

1. educe cost 2.ncrease stiffness. 3.educe mold shrin#age. $. "ontrol viscosity.

&.*roduce smooth surface.

$. T)PES OF COMPOSITES

The three most important re4uirements for materials which are to be used in highly

demanding applications are a high resistance to plastic deformations, resistance to fracture and

elastic stiffness. Fibre reinforced composites can be further divided into those containing

discontinuous or continuous fibres. Today, the most common man made composites can be

divided into three main groups?

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&. MICRO MEC%ANICS

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M*t+i, Reinfo+e

P*!e

Met*/ Ce+*0i Po/"0e+

Met*/ *owder metallurgy

imparts < combining

immiscible metals

"ermets (ceramic!

metal composite)

:ra#e pads

Ce+*0i "emented carbides

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