# Presentation: 141708

## Microstructure Analysis ofAdvance Materials

- Microstructure Analysis ofAdvance Materials

- By: Ayanna Anika Moses
-       Medgar Evers College, CUNY
- PI: David Hull
-      Analytical Science Group
-      Advanced Metallic  Branch

## Objective

- Understand the procedures behind 	metallurgical analysis
-      * Mounting and polishing material 	samples
-      * Viewing the microstructure of alloys         	on the Scanning Electron 	Microscope and optical microscopes
-      *Using Interference layering for phase 	analysis
- Aid the Analysis group in completing 	evaluations on Kevlar, and 	carbon fiber composites

## Background

- Kevlar
-     Long molecular chain produced from  poly-paraphenylene terephthalamide with strong 	interchain bonding.
-     Properties include high tensile strength, low 	electrical conductivity, high chemical 	resistance, low thermal shrinkage, and high 	cut resistance.
-     Applications include bullet proof vest for police officers, run flat tires, ropes that secure the airbags in the crucial landing apparatus of the Mars Pathfinder, and bullet proof coating on ISS module.

## Background 1

- Kevlar on the gaseous tanks
-  The gaseous nitrogen supply tanks in the crew compartment of the orbiter are encased in Kevlar fiber over titanium liner. It’s highly pressurized at 3,300 psia at 80 oF
-  During the vessel proof process most of the creep on Kevlar was taken up, thus reducing the fiber stress ratio and the life expectancy of the tank.

**Macro view of sample**

-  Effect of Kevlar fiber creep on the burst strength of Kevlar/Epoxy vessels.

## Analysis begins ...

- Begin  analysis with as-received samples.
-   metallographic analysis shows fractures in the core of the Kevlar

- Colored image depicting two-toned  Kevlar tow fibers.

## Analysis begins ...

- SEM images of as received sample
- Relief on the edges mainly due to polishing of the epoxy versus the Kevlar

- Fractures on the outer layer of the Kevlar-was this created during polishing or from the manufacturing process.

## ... and continues ...

- ... and continues ...

- Kevlar that was crept:

- Many kinks in the strands though the molecular geometry did not change after creep testing.

## Background 2

- Carbon Fiber Reinforced Composites
- Proposed material for the control surface of the re-entry vehicles
-  Specimens tested under stress rupture conditions at 800 oC using a stress of 30 psi and 5000ppm oxygen/remaining argon..
-   Silicon carbide coating on carbon fibers with boron carbide between the tows to “eat” oxygen that enters the composite.
- Part of the sample is coated with a glass sealant and thus expect reduced amount of the boron oxide grains.

## Analysis begins...

- Metallographic image before interference layering

- Image depicting recrystallized grains of Boron oxide within the tows of the graphite fibers

## Analysis begins...

- Microscopic view of fractured region and the composition of the recrystallized region.
- Image illustration the variation in chemistry of the ceramic composite.

- Interference layering depicts the elemental variation of the graphite sample

## ... and continues ...

- ... and continues ...

- Interference layering         vs         SEM at high magnification

- Interference layering depicts phase and chemical variations while the SEM image limits the difference we can see.

- SiC

- Si rich

## ... and continues ...

- ... and continues ...

- Where is the Silicon coming from????

- C fiber

-  Si

## What’s  was next ...

- Kevlar:
-  Interference layering and Raman spectroscopy
-  Begin mounting and polishing the creep and tensile fibers
-  Assess damage for the fibers and determine whether they should be used for tank enhancement.
- Carbon fiber reinforced composites:
-  SEM and microprobe analysis on the graphite samples
-  Deliver images to the main man for complete analysis
-  Persuade Mr. Calomino to let me use some of his RCC samples

## Acknowledgements

- The Glenn family in the Materials Division
-  David Hull and Joy Buehler
-  Frances Hurwitz
-  Anthony Calomino and Michael Verrilli
- Medgar Evers College Family
-  Shermane Austin and Leon Johnson
-  Ohio Space Grant Consortium

## ?

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