Date of Award

9-2002

Document Type

Thesis

Degree Name

Master of Science in Materials Science and Engineering (MSMSE)

Department

Materials Science

First Advisor

Adel Hammami,

Second Advisor

Abdel-Hamid . Mourad,

Abstract

Fiber reinforced polymer (plastic) FRP composites are different from traditional

structural materials such as steel or aluminum since the an-isotropic nature of a Fiber _ reinforced composite material creates a unique opportunity of tailoring its properties according to the design requirements. With the accelerated change in the technological sphere, FRP composite materials

have taken a paramount importance in various structural applications, where they successfully replaced conventional materials such as steel. Such success is based on the advantages offered by composite materials such as a high strength to weight ratio. However one aspect that is still delaying full acceptance of these materials is their long-term behavior especially in Adverse environments such as sun and moisture exposure, seawater and corrosive fluids. Although extensive work was performed for epoxy based composite materials, however few studies addresses the issue of using vinyl ester resin as a matrix, for that reason. This study is concerned with the issue of evaluating the long-term performance of Glass fiber-reinforced composites material based on vinyl- ester resins under different environmental conditions.

This investigation explore newly touched subject in the UAE and since environmental factors such as long exposure to high temperature, and humidity are the most dominant, this research comes as an attempt to evaluate their effects on the properties and performance of composite

he mechanical properties of the composite such as corrosive fluids and moisture absorption are also investigated for such approach samples were made using two processing techniques. The techniques were hot press molding and vacuum infusion molding. The samples were then divided into five groups each one containing thirty specimens. Each of the five groups was exposed to specific environment. While some samples were exposed to hot and dry environment at Al-Ain city, others were exposed to hot and humid environment at Abu­ Dhabi. Furthermore, some samples were subjected to 5% nitric acid, 2% nitric acid and seawater at the material laboratory.

The evaluation process was divided into two intervals of three and six month's duration. The results of the three months observations showed that for moisture and sun exposure there was an,increase of the flexural strength compared with virgin samples as a result of post curing achieved after several days at room temperature. For corrosive fluids, it was evident that the increase the acid concentration will lead to a decrease in flexural strength. Moreover, there were insignificant variations in interlinear shear strength

(IL SS) and impact strength because of good matrix properties and fiber-matrix interface bonding. On the other hand a six months exposure time for the composite under ultraviolet radiations and moisture showed small variations in flexural properties compared with three months intervals. However, with respect to corrosive fluids the composite showed a very good chemical resistance and the degradation process was directly proportional to the acid concentrations.

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