Blending of Composite materials

Some Definitions Composite materials A material system composed of two or more physically distinct phases whose wise combination produces aggregate properties that are different from those of its components.

A composite material consists of two phases: Primary Forms the matrix within which the secondary phase is imbedded, any of three basic material types:- Secondary Referred as the imbedded phase or called the reinforcing agent.Serves to strengthen the composite. (fibers, particles, etc.) Can be one of the three basic materials or an element such as carbon or boron

Classification of composite material Metal Matrix Composites (MMCs) Include mixtures of ceramics and metals, such as cemented carbides and other cermets, as well as Aluminum or Magnesium reinforced by strong, high stiffness fibers Ceramic Matrix Composites (CMCs) Least common composite matrix. Aluminum oxid and silicon carbide are materials that can be imbedded with fibers for improved properties, especially in high temperature applications Polymer Matrix Composites (PMCs) polymer is the matrix like Epoxy and polyester

Polymer – Poly meaning many and mer meaning unit. Terminologyy Polymer – Poly meaning many and mer meaning unit. Monomers – Basic building block of a polymer. Macromolecules – extremely large collections of molecules to form one unit. Plastics – a synonym for polymers. Copolymers contain two types of polymers Terpolymers contains three types of polymers Amorphous, the polymer chains exist without order. Crystallites, the regions arrange themselves in an orderly manner as Crystallinity increases polymers become hard Synthetic – manmade Chapter 19 IT 208

Matrix material serves several functions in the composite provides the bulk form of the part or product- -holds the imbedded phase in place -shares the load with the secondary phase

Fibers Particles Flakes The Reinforcing Phase The imbedded phase is most commonly one of the following shapes: Fibers Particles Flakes

The Reinforcing Phase Orientation of fibers is an important consideration. One-dimensional maximum strength and stiffness are obtained in the direction of the fiber Planar in the form of two-dimensional woven fabric Random or three-dimensional the composite material tends to posses isotropic properties

Fiber Loading Effect under Stress

Structures of Polymers Linear Polymers Branched Polymers Increase resistance to deformation and stress cracking. Cross Linked Polymers (Thermosets) have a major influence in polymers. Imparting hardness, strength, stiffness, brittleness, and better dimensional stability. Networked Polymers (highly cross linked), have a higher strength when exposed to high energy radiation, UV light, x-rays, or electron beams

Thermoplastics The word plastic comes from the Greek word plastikos, meaning capable of being molded and shaped. The earliest polymers, such as cellulose, were made from natural organic materials from animals and vegetable products.

POLYMER MATRIX COMPOSITES Hybrids When two or more fibers materials are combined in the composite. Intraply hybrids (within) - Alternate strands of different fibers in a single layer or ply . Interply hybrid (across) – Different plies of different fiber. The most widely used form if a laminar structure, made by stacking and bonding thin layers of fiber and polymer until the desired thickness is obtained.

Polymer blends blends is the mixtures that are not fully compatible while alloy are mixture which fully compatible. Polymer blends are physical mixtures of two or more polymers or copolymers. with/without any chemical bonding between them. The objective of polymer blending is a practical one of achieving commercially viable products through either unique properties or lower cost than some other means might provide. Property of polymer blends is superior to those of component. homopolymers. The term (homo polymer) is used to describe those polymers that are made up of just one monomer.

Types of Polymer Blends On the basis of miscibility Completely miscible(single phase) blends , Homogeneity is observed at least on a nanometer scale, if not on the molecular level.This type of blends exhibits only one glass transition temperature (Tg), which is in between the glass transition temperatures of the blend components in a close relation to the blend composition. A well-known example of a blend, which is miscible over a very wide temperature range and in all compositions is PS/PPO

In partially miscible blends a small part of one of the blend component is dissolved in the other part. This type of blend, which exhibits a fine phase morphology and satisfactory properties, is referred to as compatible(exhibits macroscopically uniform physical properties). Both blend phases are homogeneous, and have their own Tg. In this case interface is wide and the interfacial adhesion is good.

Immiscible Polymer Blend (Heterogeneous Polymer Blend): A polymer blend may exhibit immiscibility, which means the inability of its mixture to form a single phase. Immiscibility of a polymer blend may be limited to certain ranges of temperature pressure and composition. It normally depends on the chemical structures, molar mass distributions and molecular architectures of the components

How to blend Chapter 19 IT 208

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Fully immiscible blends have a coarse morphology, sharp interface and poor adhesion between the blend phases. So these blends are of no use without compatibilisation. The blends will exhibit different Tgs corresponding to the Tg of the component polymers. Examples of fully immiscible blends are ep/ps, PA/PPO, PA/EPDM and PA/PP. Now these blends have become commercially successful, after being efficiently compatibilised using suitable compatibilisers

immissable polymers Chapter 19 IT 208