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 Concept of Interfacial Reaction in

Textile Composites

K.Srikanth11MT72M.tech  – Textile Technology (PT)

PSG Tech

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Fiber-Matrix interface

Nano-sized boundary between fibres andmatrix Interface

boundary between any two phases drop change of  chemical and

physical properties

- result of  two surfaces interaction, that depends on the surface structure and 

properties of  both phases

- the structure and properties of  interface differ  from both phases

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Each system possess specific interface

Ideal interface- infinitely thin, tight, no defects

Real interface

- complicated chemical and physical structure

Important influence on composite properties

e.g.

fracture toughness corrosive behaviour 

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In composites are important

The structure of  interface

Physical properties of  interface 

mechanical

great difference between mechanical properties of  fibres and matrices

the tension is transferred from matrix to fibres through the interface

other  important properties  – electrical, Optical, thermal

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Voids in Interface

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De-bonding in Interfaces

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Impact of joining components on interfaceproperties

Various layers

different properties

no chemical bonds, no physical  joining

no tensile strength of  composite

- in-plane modulus depends on the specimen clamping

 All layers tightly fixed in  jaw CLIP EFFECT

- all layer  carry tension

Strength and stiffness of  composite

- fibres are bonded by matrix

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Composites with weak interface

- lower  strength and stiffness

- more flexible

Composites with strong interface 

high strength and stiffness hard, brittle

Character of joining between fibres and matrix 

- atomic distribution

- chemical properties of  fibres

- conformation and chemical properties of  matrices

Strength of joinings is affected by ADHESION

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Mechanisms of adhesion

Five main mechanisms

- joining between fibres and matrices

- they work either  separately or  in conjunction

 Adsorption and wetting

Interdiffusion

Electrostatic attraction Chemical bond

Mechanical adhesion

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Adsorption and wetting

 Adsorption

 Adsorption is the accumulation of  atoms or  molecules on the surface of  material

This process creates a film of  the adsorbate (the molecules or  atoms being

accumulated) on the adsorbent's surface

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Wetting

Wetting of  real surface:

- Two electrically neutral, hard, rough surfaces

- also roughnesses in microscopic scale

- contamination by oxides, dust particles etc.

- contact points only

Improvement of  wetting

- cleaning and smoothing of  surface

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Interdiffusion 

strength of   joining is influenced by

- number  of  diffusive molecules conformation of  molecules

- molecular  movement

- entanglements

Electrostatic attraction

 Two oppositely charged surfaces

- interaction of  acid and base 

oppositely charged ions

- positively charged groups on molecular  ends are attracted by  anions rised from polymer  orientation

- strength of  interface depends on charge density 

- it is not wet-stable

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Chemical bond

- chemical groups on fiber  surface

+ compatible chemical group of  matrix 

Mechanical adhesion

- Two surfaces are  just mechanically stucked 

- high shear  strength

- depends on size of  irregularities

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 Mechanical adhesion 

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Thank U!!!