COMPOSITE MATERIALS IAD 232 Ass. Prof. Dr. Işıl DUMAN

WHAT ARE THEY? Through ages, man have become more innovative in discovering new materials, cost reduction techniques aiding life to exist far more better. A combination of dissimilar materials which retain their individual characteristics yet achieve performance that surpasses the combined performance of the individual materials. The constituent materials work together yet remain in their original physical forms and chemical compositions, they are not chemically combined

W HAT IS A COMPOSITE MATERIAL ? Often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or microscopic scale within the finished structure.

two materials in which one of the materials, called the reinforcing phase, is in the form of fibers, sheets, or particles, and is embedded in the other materials called the matrix phase. The reinforcing material and the matrix material can be metal, ceramic, or polymer. Composites are used because overall properties of the composites are superior to those of the individual components.

C OMPOSITE MATERIALS Definition: any combination of two or more different materials at the macroscopic level. OR Two inherently different materials that when combined together produce a material with properties that exceed the constituent materials. Reinforcement phase (e.g., Fibers) Binder phase (e.g., compliant matrix) Advantages High strength and stiffness Low weight ratio Material can be designed in addition to the structure

Wattle and daub is one of the oldest manmade composite materials, at over 6000 years old. Concrete is also a composite material, and is used more than any other man-made material in the world. As of 2006, about 7.5 billion cubic metres of concrete are made each year—more than one cubic metre for every person on Earth. A wattle and daub panel in need of repair

1940s and 1950s, aerospace industry looked at high performance composites as replacement for steel. Early materials were glass fiber and polyester resin. Limited to non-structural applications. Resin and fibers developed and material systems matured. During the 1960s new fiber systems were developed for structural components High strength glass fibers (S-901), Aramid(Kevlar 49), carbon and graphite systems

WHY COMPOSITES? High specific strength (strength/density) High specific modulus (modulus/density) Fatigue resistance Creep and creep rupture resistance Low, tailorable coefficient of thermal expansion High temperature capability Wear resistance Corrosion resistance Tailorable electrical conductivityVery low to very high

WHY COMPOSITES? Tailorable thermal conductivity very low to extremely high Tailorable mechanical and thermal properties Unique combinations of properties Great design flexibility Formable to complex shapes Low cost (some) Enabling technology for many applications, e.g.Lightweight vehicle and aerospace structures High-performance thermal management Lightweight optical systems Infrastructure repair

T YPES OF C OMPOSITES Particle-reinforced composites Fiber-reinforced composites Structural composites

P ARTICLE - REINFORCED COMPOSITES * Used in particle reinforcing - ceramics, glasses (small mineral particles) - metal particles (aluminium, and amorphous materials ) polymers and carbon black Particles are used to increase the modulus of the matrix, to decrease the permeability of the matrix, to decrease the ductility of the matrix and also used to produce inexpensive composites.

E XAMPLE : CONCRETE where the aggregtes ( sand and gravel) are the particles and cement is the matrix. Particle reinforced composites support higher tensile, compressive and shear stresses.

F IBER - REINFORCED COMPOSITES Fiber-reinforced Composites are made of: - metals, ceramics, glasses, or polymers that have been turned into graphite and known as carbon fibers. - Fibers increase the modulus of the matrix material. (strong covalent bonds along the fiber's length gives them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved )

U SES OF F IBER - REINFORCED COMPOSITES sports equipment, such as a time-trial racing bicycle frame which consists of carbon fibers in a thermoset polymer matrix. Body parts of race cars and some automobiles are composites made of glass fibers (or fiberglass) in a thermoset matrix Fiber orientation in fiber reinforced composites.

S TRUCTURAL COMPOSITES The properties of structural composites depend on: - Constituents - Geometrical design

C OMMON C OMPOSITE M ATERIALS < ASPHALT FIBER GLASS > < CEMENT PLYWOOD>