# Presentation: 279793

## High Temperature Composites

- Rutgers University
- Federal Aviation Administration
- Advanced Materials Flammability
- Atlantic City, NJ
- October 24, 2001

## Research Team

- P. Balaguru
- J. Giancaspro
- C. Papakonstantinou
- R. Lyon   (FAA)

## Introduction

-  Polysialate (“Geopolymer”)
-  Aluminosilicate
-  Water-based, non-toxic, durable
-  Resists temperatures up to 1000°C
-  Curing temperature:  20, 80, 150°C
-  Protects carbon from oxidation

## Ongoing Research at Rutgers

- Mechanical properties of carbon and glass composites
- Hybrid composites: carbon/glass and inorganic/organic
- Structural sandwich panels
- Comparison with other high temperature  composites

## Hybrids:  Fiber Characteristics

- Glass – Economical, larger fiber diameter
- Carbon – Higher modulus and strength, durability

## Variables

- Eglass fiber core with carbon fiber skins
- Number of layers on tension side: 1,2,3
- Type of carbon fabric: 1k and 3k woven, 3k unidirectional
- Number of layers on the compression side: 1,2,3
- Specimen thickness:  6, 12, and 18 layers of glass fabrics

## Specimen Preparation

- Hand impregnation
- Room temperature (20°C) curing
- 1 MPa of pressure for 24 hours
- Post curing for 3 weeks
- Room temp. curing reduces degradation of glass under alkali environment

## Test Setup

- Simply supported
- 3-point bending (ASTM D790)
- Loading rate = 2.5 mm / min

## Mechanical Properties

- Load – deflection response converted to stress and strain
- Stress,
- Strain,

## Assumptions for Analysis

- Homogeneous
- Elastic
- Uncracked section
- Perfect bond between glass and carbon layers

## Glass / Carbon Hybrid Results

- Density
- Failure pattern
- Peak stress (strength)
- Strain at peak load (ductility)

## Density

- All glass:  2.36 g/cm3
- All carbon:  1.9 to 2.0 g/cm3 for 3 types
- Increase in carbon layers provide consistent decrease in density

## Failure Pattern

- Glass:  brittle, no post-cracking strength
- Glass with 1 and 2 carbon layers:  failed in tension
- Glass with 3 carbon layers:  compression failure
- Glass with both tension and compression reinforcement:  compression failure

## Slide 14

**Notes:**
Details of samples

## 3k Unidirectional Carbon

- _3k Unidirectional Carbon_

**Notes:**
Figure 1

## Samples with 2 Carbon Layers

- _Samples with 2 Carbon Layers_

**Notes:**
Figure 2

## Varying Sample Thickness

**Notes:**
Figure 3

## Maximum Stress: 3k Uni Carbon

- Pure Glass:   103 MPa
- Glass + 1 Layer:   212 MPa
- Glass + 2 Layers:  379 MPa
- Glass + 3 Layers:  354 MPa
-  3k Unidirectional Carbon: 466 MPa

## Thickness vs. Maximum Stress

- 6 Glass + 1 carbon (uni):  347 MPa
- 12 Glass + 2 carbon :  379 MPa
- 18 Glass + 3 carbon :  362 MPa

## Maximum Strains

- Matrix  (tension):  0.0007
- Matrix (compression):  0.005
- All Glass (tension):  0.003

## Maximum Strain: 3k Uni Carbon

- Pure Glass:   0.003
- Glass + 1 Layer:   0.007
- Glass + 2 Layers:  0.011
- Glass + 3 Layers:  0.009
-  3k Uni Carbon:  0.005

## Thickness vs. Maximum Strain

- 6 Glass + 1 carbon (uni):  0.012
- 12 Glass + 2 carbon :  0.011
- 18 Glass + 3 carbon :  0.011

## Conclusions: Glass/Carbon Hybrids

- Eglass / carbon is a viable combination.
- For all types of carbon fabric, 2 layers on the tension side provides the highest strength.
- Placing carbon on both compression and tension faces does not significantly increase the strength.

## Conclusions: Glass/Carbon Hybrids

- Eglass reinforced with 1, 2, or 3 carbon layers exhibited the highest strength when the fabric was 3k unidirectional
- Slightly lower strengths were achieved using 3k woven carbon fabric
- The lowest strengths were achieved using 1k woven carbon fabric

## Conclusions: Glass/Carbon Hybrids

- The uncracked section modulus for Eglass reinforced with 1k or 3k woven on the tension side showed little change as the number of carbon layers increased.
- 3k unidirectional carbon on the tension side provided a modulus increase with an increasing  number of layers.
- An increase in modulus also results for carbon on both compression and tension sides.

## Strain Capacity of Polysialates

- Cantilever Beam Method

## Variables Investigated

- Silica / Alumina ratio
- Discrete carbon fiber content
- Effect of ceramic micro-fibers

## Influence of Carbon Fiber Content on Cracking Strain

## Effect of Microfibers

- Without Ceramic Microfibers

- With Ceramic Mircofibers

## Durability

- Wet-Dry
- Flexure
- [±45°] In-Plane Shear
- Thermo-mechanical
- Exposure Temperatures (200, 400, 500, 600°C)

## Wet – Dry Durability

## Comparison of Polysialate and Other Inorganic Composites

- Relative performance of polysialate composites
- Processing requirements
- Mechanical properties
- Carbon/Carbon composites
- Ceramic matrix composites
- Carbon/Polysialate composites

## Stress vs. Strain Relationships of Bi-directional Composites in Tension 

## Tensile Strength of Bi-directional Composites 

## Flexural Strength of Unidirectional Composites 

- _Flexural Strength of Unidirectional Composites_

## Flexural Stress-Strain Relationships of Unidirectional Composites 

## Flexural Strength of Bi-directional Composites 

## Lightweight Sandwich Panels

- Core features:
- -  Inorganic matrix + ceramic spheres
- -  Density:  0.6 to 0.7 g/cm3
- -  Compressive strength:  5.12 MPa
- Carbon fabric laminated onto facings

## Typical Section of Sandwich Slab (Panel)

-  Carbon facings on both tension and compression sides

- _Typical Section of Sandwich Slab (Panel)_

## Flexural Strength of Slabs With Different Reinforcement

- _Flexural Strength of Slabs With Different Reinforcement_

## Load vs. Deflection for Slabs

- _Load vs. Deflection for Slabs_

## Future Research

- Commercially available plates  +  Inorganic matrix layer
- Glass plates
- Carbon plates
- Fatigue
- Sandwich panels