Fiber Composite Materials

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Composite Materials Laboratory Report

Introduction to Materials Engineering (MatE25)
Lab Section 8

by
Carolyn Jaring

Laboratory Instructor:
Joshua Moore

March 11, 2014

Introduction
Composites are materials that are made out of two or more constituent materials with significantly different mechanical properties which when combined produce an overall material that is better than the individual components. Different types of composites include Ceramics, Composite Building Materials, Fiber-reinforced materials, and metal composites. Fiber reinforced materials are made up of axial particulates that are embedded within a matrix. The matrix of this said composite is epoxy. Epoxy is a thermoset polymer. Polymers are made up of long carbon chains that are linked together. Their mechanical properties varies with the way and degree of how and to what extent the chains are cross-linked together. Thermoset polymers form networks of chains with a great degree of polymerization, thus making the polymer brittle and hard. To counter this failure, a fiber that will add strength to the polymer will be added, thus, making a strong fiber-reinforced composite. The purpose of this research is to compare and contrast different fiber reinforced composite that are suitable replacement for some steel parts of a hybrid car based on its weight, cost, yield strength, and ultimate tensile strength. To compare the strength of different types of fiber, the team used only one fiber geometry for three fiber reinforced composites with different fiber materials in each dog bone sample.

Experimental Procedure
Since a uniaxial tension is going to be utilized for a structural loading application, the team decided on one type of filling and f...

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...d using Instron and a graph showing the flexure stress and strain was printed. Figures were calculated and compared with the theoretical calculations based on the reference book by Callister. The results showed that using a carbon fiber and epoxy yields the best ultimate tensile strength (86 MPa) and modulus (1.9 GPa) while being the cheapest, only costing $0.92 per dog bone sample. Some useful recommendations for future experiments would include different fiber geometries/arrangements. Placing the fiber at the bottom of the dog bone sample would definitely change the three-point bend test results.

Reference
Callister, Materials Science and Engineering: An Introduction 8th Edition, (John Wiley and Sons, New York), Chapter 14, 15, & 16.
Materials Engineering Department, “Chapter 9: Composites”. Introduction to Materials Laboratory Manual. San Jose State University.

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