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Nondestructive testing of defects in adhesive joints

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particles. Additionally, fractured surface are observed under an Optical metallurgical microscope to<br />

<strong>in</strong>vestigate both particle dispersion and evidence <strong>of</strong> extr<strong>in</strong>sic toughen<strong>in</strong>g mechanism. It is observed that<br />

the both improved particle dispersion and appropriated silane treatment lead to <strong>in</strong>crease <strong>in</strong> toughness. [3].<br />

Epoxy has excellent electrical, thermal and chemical resistance. Shr<strong>in</strong>kage dur<strong>in</strong>g polymerization<br />

<strong>of</strong> epoxy res<strong>in</strong>s is extremely low. Molded epoxy parts are hard, rigid, and relatively brittle and have<br />

excellent dimensional stability over a broad temperature range. Epoxy is readily mach<strong>in</strong>able and can be<br />

employed over temperature range <strong>of</strong> 60 to 250° C. Alum<strong>in</strong>um has only one-third the weight <strong>of</strong> steel.<br />

Alum<strong>in</strong>ium powder was used as filler material for epoxy res<strong>in</strong> to obta<strong>in</strong> good mechanical properties and<br />

high thermal capabilities and fatigue resistance.<br />

Spheriglass solid glass spheres are microspheres with a density <strong>of</strong> 2.5g/cc. The addition <strong>of</strong><br />

spheriglass to epoxy system does not alter viscosity <strong>of</strong> the epoxy system. These spheres are nonporous.<br />

They do not absorb res<strong>in</strong> <strong>in</strong> polymer system.<br />

EXPERIMENTAL<br />

MATERIALS USED.<br />

DGEBA liquid epoxy res<strong>in</strong> (LY556) with epoxy equivalent around 170 and viscosity <strong>of</strong> 8000 to<br />

12000 cp at 25 degree Celsius was used as received from Araldite India Pvt. Ltd.Organo modified<br />

polysiloxane with molecular weight around 5000 was used as liquid rubber modifier as received from<br />

Resil chemicals Pvt Ltd. Triethylene tetram<strong>in</strong>e (HY 951-cur<strong>in</strong>g agent) was used as received from Araldite<br />

India Pvt.Ltd.Alum<strong>in</strong>ium and spheiglass were received from Potter <strong>in</strong>dustries Inc.<br />

PREPARATION OF LIQUID RUBBER MODIFIED EPOXY MATRIX.<br />

Am<strong>in</strong>e conta<strong>in</strong><strong>in</strong>g polydimethylsiloxane was taken as liquid rubber modifier. Five phr or ten phr<br />

<strong>of</strong> liquid rubber modifier was taken along with epoxy res<strong>in</strong> and the mixture was heated at 50 degree<br />

Celsius for 30 m<strong>in</strong>utes with cont<strong>in</strong>uous stirr<strong>in</strong>g. Then the liquid rubber modified epoxy res<strong>in</strong> was allowed<br />

to cool <strong>in</strong> the room temperature.<br />

PREPARATION OF ALUMINUM AND SPHERIGLASS FILLED EPOXY AND MODIFIED EPOXY<br />

MATRIX<br />

The weighed amount <strong>of</strong> spheriglass was added to epoxy system and stirred for 15 m<strong>in</strong>. Then<br />

weighed amount <strong>of</strong> alum<strong>in</strong>um was added to the spheriglass/epoxy system and stirred for 15 m<strong>in</strong>. This tri-<br />

phase material was cured us<strong>in</strong>g triethylene tetram<strong>in</strong>e at room temperature. The same procedure was<br />

carried out for Am<strong>in</strong>e conta<strong>in</strong><strong>in</strong>g PDMS modified epoxy matrix. The material was cured at 100°C for 3<br />

hrs.<br />

Various percentages <strong>of</strong> Alum<strong>in</strong>um and spheriglass filled epoxy res<strong>in</strong> are as follows:

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