**Poly-siolate Composites**

FINAL REPORT

December 2007

Submitted by

P.N.Balaguru, Principal Investigator,

Professor of Civil Engineering

Rutgers University

Research Project Manager

Dr. Richard Lyon

FAA

U. S. Department of Transportation

Federal Highway Administration

## DISCLAIMER STATEMENT

The contents of this report reflect the views of the author(s) who is
(are) responsible for the facts and the accuracy of the data presented
herein. The contents do not necessarily reflect the official views or
policies of the New Jersey Department of Transportation or the Federal
Highway Administration. This report does not constitute a standard,
specification, or regulation.

**ACKNOWLEDGEMENTS**

The author wish to thank Dr. Richard Lyon, Research Program Manager, FAA
for providing funding and technical/scientific help at the various
stages of the project, without whom this project would not have been
possible. I also appreciate the help of Drs. Mohamed Arafa, Mohamed
Nazier, James Giancaspro, Christos Papakonstantinou, James Hammell,
Andrew Foden, Mr. Philip Feltz and Mr. Christian DeFazio for their
contributions. Support from National Science Foundation and other
agencies for related work is also acknowledged with thanks.

**Summary**

The research support was used to support seven doctoral students, two MS
students and five undergraduate students. Five doctoral students were
supported fully and two of them were supported partially. The MS and
undergraduate students were supported partially. One undergraduate
student wrote a thesis. The Principle Investigator obtained a number of
other grants to leverage the funds provided by FAA.

The research resulted in a large number of publications, presentations
and book chapters. Some of the students are pursuing further research in
this area. The abstracts of the various dissertations provide the gist
of the research at various stages. Therefore, abstracts are presented as
part of this report. The conclusions of four of the last dissertations
are also presented. These conclusions incorporate findings of the
previous dissertations.

The major outcome of the research effort is as follows.

Feasibility of manufacturing high strength composites using polysiolates
was established. T fiber types consisted of: aramid, basalt, carbon,
glass, Nextel and silicon-carbide.

Strength and durability of these composites were evaluated. Carbon
composites were also tested under fatigue loading.

The composites can withstand 800 C for all formulations. Nextal fiber
composites can withstand 1500 C

Strength properties are lower than organic composites because the matrix
is brittle. However, this composite is better than all other
ceramic-fiber composites. Low temperature curing allows the use of
carbon fibers.

Sandwich plates were fabricated using balsa wood and various types of
organic and inorganic foams.

It is feasible to manufacture sandwich plates using organic and
inorganic cores.

Sandwich beams made using inorganic core can withstand 800 C
indefinitely.

Sandwich beams made with organic core can be protected using
polysiolates against fire. The same is true for balsa wood.

Related projects were responsible for the development of fire-proof
strengthening mechanism for various structural components and
development of coatings that are fire-proof, durable, self-cleaning and
has de-pollution properties.

The work of one of the undergraduate student on high temperature
behavior of polysiolate-wood composite received best paper (third place)
in SAMPE 2005.

The PI was invited to present the highlights of research for the
National TV program of *Science and Technology*

This report contains the details of the participating students, support
from other agencies for related research, publications, presentations
and the scientific outcome of the research. Abstracts and selected
conclusions from doctoral, masters and undergraduate thesis research are
used to present the scientific outcome.

**TABLE OF CONTENTS**

Summary

Participating Doctoral, Masters and Undergraduate students

Publications

Presentations

Abstracts and Conclusions of Dissertations

Participating Doctoral, Masters and Undergraduate students

**Students Name: Andrew Foden**

**Title: Mechanical Properties and Material Characterization**

**of Polysialate Structural Composites**

**Year of Graduation: 1997**

**Current Position: Senior Structural Engineer, Parsons and
Brinkerhoff**

**Students Name: James Hammell**

> **Title:** THE INFLUENCE OF MATRIX COMPOSITION AND REINFORCEMENT
>
> TYPE ON THE PROPERTIES OF POLYSIALATE COMPOSITES

**Year of Graduation: 2000**

**Current Position: Senior Structural Engineer, Fluor**

**Students Name: James Giancaspro**

**Title: Influence of Reinforcement Type on the Mechanical Behavior and
Fire Response of Hybrid Composites and Sandwich Structures**

**Year of Graduation: 2004**

**Current Position: Assistant Professor, University of Miami**

**Students Name: Christos Papaconstantinou**

**Title:** High Strength High Temperature Sandwich Composites

**Year of Graduation: 2004**

**Current Position: Assistant Professor, University of Massachusetts
Dartmouth**

**Students Name: Mohamed Nazier**

**Title: Evaluation of High Strength Composites and New Construction
Techniques for their Effective Use**

**Year of Graduation: 2004**

**Current Position: Structural Engineer, Parsons**

**Students Name: Mohamed Arafa**

**Title:** HIGH STRENGTH-HIGH TEMPERATURE LAMINATED SANDWICH BEAMS

**Year of Graduation: 2007**

**Current Position: Structural Engineer, Shewareds Associates**

**Students Name: Christian DeFazio**

**Title:** HIGH TEMPERATURE/ HIGH STRENGTH DISCRETE FIBER

**Year of Graduation: 2007**

**Current Position: Structural Engineer, Thornton and Thomashetty**

**Students Name: Philip Feltz**

**Title:** AN INVESTIGATION OF THE USE OF BIOMASS WASTE PRODUCTS FOR
CREATING INORGANIC POLYMER COMPOSITES, AND THE INFLUENCE OF
REINFORCEMENT ON THE MECHANICAL BEHAVIOR AND FIRE RESPONSE OF SANDWICH
STRUCTURES

**Year of Graduation: 2006**

**Current Position: Construction Engineer, Conti Construction**

**Related Research Projects supported by other Agencies and
Collaborations**

Self Cleaning Coatings, National Science Foundation, May 2005-April
2006, \$89,000. Principal Investigator.

Development High Temperature Geopolymer, AFSOR, May 2004-May 2006,
\$84,000. Principal Investigator.

Field Application of Geopolymer Coating, Maryland DOT, June2003-June
2005, \$15,000. Principal Investigator.

Field Application of Geopolymer Coating, NJ DOT, June2003-June 2005,
\$10,000. Principal Investigator.

Construction and Evaluation of Fiber Composite Caps for Protection of
Piers and Pier Caps, Federal Highway Administration (FHWA). Innovative
Projects (through R.I. DOT, URI), November, 2001-October 2005, \$287,057
. Principal Investigator.

Evaluation of an Inorganic Resin for Strengthening Reinforced Concrete
and Steel Beams, National Science Foundation, September 15, 1999-August
2001, \$66,772. Principal Investigator.

Field Application of Geopolymer, NJDOT, June 2000 - May 2002, \$61,431.
Principal Investigator.

\"Effectiveness of Fiber Reinforced Composites as Structural and
Protective Coverings for Bridge Elements Exposed to Deicing-Salt
Chlorides, New England Consortium of DOT, August 31, 1997-December,
2000, \$135,000, Principal Investigator.

Geopolymer for Graffiti Proof Coating, NJDOT, July 1997-June 1998,
\$35,000, Principal Investigator.

**Publications**

Papakonstantinou C.G., Balaguru P., "Fatigue Behavior of High
Temperature

Inorganic matrix composites", [Journal of Materials
Engineering]{.underline}, ASCE, Vol.19,

No.4, April 2007, pp 321- 328

Najm, H., Secaras, J. and Balaguru, P. "Compression Tests of Circular
Timber

Column Confined with Carbon Fibers Using Inorganic Matrix", (TN)

[Journal of Materials Engineering]{.underline}, ASCE, Vol.19, No.2,
March-April 2007,

pp 198- 204.

Zhao, Q., Nair, B. and Balaguru, P., "Novel Geopolymer based composites

with enhanced ductility", [Journal of Materials Science]{.underline},
Springer Netherlands,

March 2007, pp 3131-3137

Nair, B., Zhao, Q., Rahimian, T., Cooper, R. and Balaguru, P., "Matrix
and

Interphase Design of Geopolymer Composites"' Ceramic Transactions, 175,

2006, pp 253-263

Giancaspro, J., Balaguru, P., and Lyon, R. "Use of inorganic Polymer to
Improve

The Fire Response of Balsa Sandwich Structures", [Journal of
Materials]{.underline}

[Engineering]{.underline}, ASCE, Vol.18, No.3, May-June 2006, pp 390-398

Najm, H. and Balaguru, P. "Rapid Hardening Concrete Mixtures", [Journal
of]{.underline}

[Materials]{.underline} [Engineering]{.underline}, ASCE, Vol.17, No.2,
March-April 2005, pp.198-206

Giancaspro, J., Balaguru, P., and Lyon, R. "Fire Protection of Flammable

Materials

Utilizing Geopolymer," SAMPE Journal, November-December 2004

> Papakonstantinou, C.G., Balaguru, P. and Lyon R.E., \"Comparative
> Study of High Temperature Composites\", [Journal of Composites,
> Part]{.underline} B: Engineering, Volume 32, Issue 8, December 2001,
> pp. 637-649

Kurtz, S. and Balaguru,P., \"Comparison of Inorganic and Organic
Matrices for Strengthening of Reinforced Concrete Beams\", [Journal of
Structural Engineering,]{.underline} ASCE, Vol. 127, January 2001. pp.
35-4

Hammell, J.A., Balaguru, P., and Lyon, R., \"Strength Retention of Fire
Resistant Aluminosilicate-Carbon Composites under Wet-Dry Conditions,\"
[Journal of]{.underline} [Composites]{.underline}, Part B: Engineering
Vol. 31, No. 2, April 2000, pp. 107-111.

Lyon, R.E., Balaguru, P., et.al. \"Fire Resistant Aluminosilicate
Composites", [Fire and Materials]{.underline}, Vol. 21, 1997, pp. 67-73.

Balaguru, P., "High Strength Composites and Infrastructures: Research
Opportunities", SAMPE International Symposium, Baltimore, MD, June,
2007.

Balaguru, P., "Inorganic Polymer Composites for Protection of Aging
Infrastructures", SAMPE International Symposium, Baltimore, MD, June,
2007.

C.G. Papakonstantinou and Balaguru, P., "Geopolymer Protective Coatings
for

Concrete", SAMPE International Symposium, Baltimore, MD, June, 2007.

DeFazio, C., Arafa, M. and Balaguru, P., "Discrete-Fiber Reinforced High

Temperature Composites", SAMPE International Symposium, Long Beach,

CA, May 2006.

Arafa, M., Balaguru, P., and Lyon, R., "Lightweight Sandwich Beams Using

Carbon/Geopolymer Facing", SAMPE International Symposium, Long Beach,

CA, May 2006.

Arafa, M. and Balaguru, P., "Flexural Behavior of High Strength-High
Temperature Laminate Sandwich Beams", Seventh International Conference
on Ferrocement, Bangkok,Thailand, February, 2006.

Giancaspro, J., Balaguru, P., and Lyon, R., "Hybrid composites with
Glass/Carbon Fibers and Inorganic Matrices", SAMPE International
Symposium, Long Beach, CA, May 2005.

Balaguru, P., Papakonstantinou, C. and Lyon, R., "Hybrid Composite
Panels with

Fireproof Lightweight Core and Carbon Fiber Skin", SAMPE International
Symposium, Long Beach, CA, May 2005.

Giancaspro, J., Balaguru, P., and Lyon, R. "Carbon-Geopolymer for Use in
structural Sandwich Elements", SAMPE International Symposium, Long
Beach, CA, May 2005

Giancaspro, J., Balaguru, P., and Lyon, R., "Fire Protection of
Flammable Materials Utilizing Geopolymer," SAMPE, Vol. 49, May 2004, pp.

Giancaspro, J., Balaguru, P., and Lyon, R., "Recent Advances in
Inorganic Polymer Composites," International Society of Offshore and
Polar Engineering, ISOPE, 2003.

Giancaspro, J., Balaguru, P., and Lyon, R., "Influence of Density on the
Behavior of Sandwich Panels," SAMPE, Vol. 48, 2003.

Christos G. Papakonstantinou, Perumalsamy N. Balaguru and Richard E.
Lyon. "Hybrid Composite Panels with Fireproof Lightweight Core and
Carbon Fiber Skin". Vol. 47, SAMPE 2002 International Symposium, May
2002, Long Beach, CA, May 2002, pp. 1011-1021.

Giancaspro, J., Balaguru, P., and Lyon, R. "Flexural Behavior of Balsa
Wood Cores Reinforced With Inorganic Carbon Composite," Vol. 47, SAMPE
2002 International Symposium, May 2002, Long Beach, CA, May 2002, pp.
530-541.

Giancaspro, J., Papakonstantinou, C. G., Balaguru, P., and Lyon, R.,
\"Inorganic Matrix Hybrid Composites,\" The Third Triennial
International Aircraft Fire and Cabin Safety Research Conference,
Atlantic City, NJ, October 8, 2001.

Balaguru, P., Giancaspro, J., and Lyon, R., \"Flexural Behavior of High
Strength Laminates with Inorganic Polymer,\" Ferro 7, Singapore, June
2001, pp. 239-246.

Balaguru, P., Giancaspro, J., and Lyon, R., \"Hybrid Composites with
Carbon/Glass Fibers and Inorganic/organic Matrices,\" SAMPE, Vol. 46 II,
2001, pp. 2582-2592.

Hammell, J., Balaguru, P., and Lyon, R., \"Wet-Dry Durability of
Inorganic Matrix/High Strength Fiber Composites for Structural Repair
and Rehabilitation,\" Concrete under Severe Conditions, CONSEC 01,
Vancouver, Canada, June 2001, pp. 1850-1857.

Hammell, J., Balaguru, P., and Lyon, R., \"Tensile Strain Capacity of
Geopolymers by Cantilever Method,\" SAMPE, May 2000, pp. .

Lyon, R. E., Foden, A., Balaguru, P., and Davidovits, J., \"Properties
of Geopolymer Matrix-Carbon Fiber Composites,\" Second International
Conference, Geopolymere, Saint-Quentin, France, June-July 1999, pp.
123-140.

Foden, A., Balaguru, P., Hammell, J., and Lyon, R., \"Flexural Fatigue
Properties of Geopolymer Matrix-Carbon Fiber Composites,\" Second
International Conference, Geopolymere, Saint-Quentin, France, June-July
1999, pp. 143-154.

Hammell, J., Balaguru, P., Lyon, R., and Davidovits, J., \"Influence of
Reinforcement Types on the Flexural Properties of Geopolymer
Composites,\" Second International Conference, Geopolymere,
Saint-Quentin, France, June-July 1999, pp. 155-164.

Hammell, J., Balaguru, P., Lyon, R., \"Behavior of Geopolymer Reinforced
with Various Types of Fabrics,\" 43rd International SAMPE Symposium,
Vol. 43, No. 1, June 1998, pp. 1600-1608.

Hammell, J., Balaguru, P., Lyon, R., \"Use of Ferrocement Theory for
Analysis of High Strength Composites,\" Ferrocement VI, June 1998,pp.
347-360.

Foden, A., Balaguru, P., Lyon, R., and Davidovits, J., \"Flexural
Fatigue Properties of an Inorganic Matrix-Carbon Composite,\" SAMPE, May
1997, pp. 1345-1354.

Lyon, E., Sorathia, V., Balaguru, P., Foden, A., and Davidovits, J.,
\"New Fire Safe Material for Cabin Interiors,\" AGARD Conference
Proceedings, 587, October 1996, pp. 27.1-27.8.

Foden, A., Balaguru, and Lyon, R., \"Mechanical Properties and Fire
Response of Geopolymer Structural Composite,\" SAMPE, March, 1996, pp.
748-758.

Foden, A., Balaguru, P., and Lyon, R., \"Mechanical Properties of Carbon
Composites Made Using an Inorganic Polymer,\" ANTEC , 1996 pp.
3013-3018.

Foden, A., Lyon, R., and Balaguru, P., \"A High Temperature Inorganic
Resin for Use in Fiber Reinforced Composites,\" Proceedings, First
International Conference on Composites in Infrastructure, NSF, Tucson,
Arizona, January, 1996, pp. 166-177.

Lyon, R., Sorathia, U., Balaguru, P., and Foden, A., \"Fire Response of
Geopolymer Structural Composites,\" Proceedings, First International
Conference in Composites in Infrastructure, NSF, Tucson, Arizona,
January, 1996, pp. 972-981.

**Presentations**

**Invited, Key Note and Plenary Papers**

"Discrete Fiber Reinforced High Temperature Composites", [Invited
Paper,]{.underline}

Ceramic Matrix Composites, 108^th^ Annual Meeting, American Ceramic
Society,

Coco Beach, Florida, January 22, 2007.(Proxy)

.

"Practical applications of Geopolymers", [Invited Paper,]{.underline}
Ceramic Matrix

Composites, 105^th^ Annual Meeting, American Ceramic Society, Coco
Beach,

Florida January 22, 2007. (With Balakrishnan Nair, Chett Boxley, and
Qiang

Zhao)

"Matrix and Interphase Design of Geopolymer Composites" with (B. G.
Nair; Cooper; Q. Zhao; T. Rahimian), [Invited Paper,]{.underline}
107^th^ American Ceramic Society, Baltimore, Maryland, April 11, 2005.

"Advances and Potential Applications of Geopolymer Composites" [Invited
Paper,]{.underline} 107^th^ American Ceramic Society, Baltimore,
Maryland, April 11, 2005.

"Inorganic Polymer Reinforced High strength Composites for High
temperature Applications", Special Seminar, University of Naples, Italy,
June 4, 2004.

> "Recent Innovations in Construction Materials", [Opening Plenary
> Paper]{.underline},

First International Conference on Innovative Materials and Technologies
for

> Construction and Restoration, Lecce, Italy, June 6, 2004.

"Recent Advances in Inorganic Polymer Composites in Repair and

Retrofit", [Plenary Paper]{.underline}, Concrete Solutions, First
International Conference on

Concrete repair, St-Malo, France, July 16, 2003

"Inorganic Composites for Repair and Rehabilitation of Offshore
structures", [Key]{.underline}

[Note Paper]{.underline}, Offshore and Polar Engineering Conference,
Honolulu, May 26,2003.

"Recent Developments in Geopolymer Composites", [Invited
Paper,]{.underline} Ceramic Matrix

Composites, 105^th^ Annual Meeting, American Ceramic Society, Nashville,
Tennessee,

April 29, 2003.

\"Recent Advances in Inorganic Matrix-High Strength Composites,\"
Society for Advancement of Materials and Processing Engineering, New
Jersey (NJSAMPE), New Jersey, September 6, 2001.

\"High Strength Advanced Composites,\" US-Germany Workshop, May 18,
1999.

\"Inorganic Matrices for Composites,\" NSF Workshop on Composites,
Hanover, NH, March 15, 1998.

\"Inorganic Polymer-Fiber Composites for Infrastructure,\" NSF Workshop,
Maracaibo, Venezuela, April 29, 1997.

**Papers Presented in National and International Conferences**

Balaguru, P., "High Strength Composites and Infrastructures: Research

Opportunities ", SAMPE International Symposium, Baltimore, MD, June 7,
2007.

Balaguru, P., "Inorganic Polymer Composites for Protection of Aging

Infrastructures ", SAMPE International Symposium, Baltimore, MD, June 7,
2007.

C.G. Papakonstantinou and Balaguru, P., "Geopolymer Protective Coatings
for

Concrete", SAMPE International Symposium, Baltimore, MD, June 7, 2007.

Arafa, M. and Balaguru, P., "Flexural Behavior of High Strength-High
Temperature Laminate Sandwich Beams" Seventh International Conference on
Ferrocement, Bangkok, Thailand, February, 2006.

Giancaspro, J., Balaguru, P., and Lyon, R., "Hybrid composites with
Glass/Carbon

Fibers and Inorganic Matrices", SAMPE International Symposium, Long
Beach,

CA, May 2005.

Balaguru, P., Papakonstantinou, C. and Lyon, R., "Hybrid Composite
Panels with

Fireproof Lightweight Core and Carbon Fiber Skin", SAMPE International

Symposium, Long Beach, CA, May 2005.

> Giancaspro, J., Balaguru, P., and Lyon, R. "Carbon-Geopolymer for Use
> in structural Sandwich Elements", SAMPE International Symposium, Long
> Beach, CA, May 2005.
>
> Giancaspro, J., Balaguru, P., and Lyon, R. "Fire Protection of
> Flammable Materials Utilizing Geopolymer," SAMPE International
> Symposium, Long Beach, CA, May 2004.

Balaguru, P. and Giancaspro, J.,"Recent Advances in Inorganic Polymer
Composites,"

International Society of Offshore and Polar Engineering, International
Symposium,

Honolulu, Hawaii, May 2003.

Giancaspro, J. and Balaguru, P.,"Influence of Density on the Behavior of
Sandwich

Panels," SAMPE International Symposium, Long Beach, California, May 13,
2003.

> Lee, K.W., Papakonstantinou, C.G., and P.N. Balaguru., "High Strength
> Composites for Strengthening and Protective Coatings", 9th
> International Conference of Composites Engineering, July 1-6, 2002,
> San Diego, California.
>
> Christos G. Papakonstantinou, Perumalsamy N. Balaguru and Richard E.
> Lyon., "Hybrid Composite Panels with Fireproof Lightweight Core and
> Carbon Fiber Skin". Vol. 47, SAMPE 2002 International Symposium, May
> 2002, Long Beach, CA, May 2002, pp. 1011-1021.
>
> Giancaspro, J., Balaguru, P., and Lyon, R. "Flexural Behavior of Balsa
> Wood Cores Reinforced With Inorganic Carbon Composite," Vol. 47, SAMPE
> 2002 International Symposium, May 2002, Long Beach, CA, May 2002, pp.
> 530-541.

Giancaspro, J., Papakonstantinou, C. G., Balaguru, P., and Lyon, R.,
\"Inorganic Matrix Hybrid Composites,\" The Third Triennial
International Aircraft Fire and Cabin Safety Research Conference,
Atlantic City, NJ, October 8, 2001.

Garon, R., Balaguru, P., and Toutanji, H., \"Performance of Inorganic
Polymer-Fiber Composites for Strengthening and Rehabilitation of
Concrete Beams, : Fiber Reinforced Plastics for Reinforced Concrete
Structures, FRPRCS-5, Thomas Telford, London, 2001, pp. 53-62.

Balaguru, P., Giancaspro, J., and Lyon, R., \"Flexural Behavior of High
Strength Laminates with Inorganic Polymer,\" Ferro 7, Singapore, June
2001, pp. 239-246.

Balaguru, P., Giancaspro, J., and Lyon, R., \"Flexural Behavior of High
Strength Laminates with Inorganic Polymers, \" Ferro 7, Singapore, June
27, 2001.

Hammell, J., Balaguru, P., and Lyon, R., \"Wet-Dry Durability of
Inorganic Matrix/High Strength Fiber Composites for Structural Repair
and Rehabilitation,\" Concrete under Severe Conditions, CONSEC 01,
Vancouver, Canada, June 19, 2001.

Giancaspro, J., Balaguru, P., and Lyon, R.., \"Hybrid Composites with
Carbon/Glass Fibers and Inorganic/organic Matrices,\" SAMPE 2001, Long
Beach, CA, May 10, 2001.

Balaguru, P., and Foden, A.J., \"Reinforcement Detailing and How it
Affects Constructability,\" American Concrete Institute Spring
Convention, Philadelphia, PA, March 27, 2001.

Hammell, J., Balaguru, P., and Lyon, R., \"Tensile Strain Capacity of
Geopolymers by Cantilever Beam Method,\" SAMPE 2000, Long Beach, CA, May
24, 2000.

Balaguru, P., and Foden, A., "Flexural Fatigue properties of Carbon
Fiber Composites,\" Geopolymer Conference, St. Quentin, France, July 2,
1999.

Hammell, J., and Balaguru, P., \"Influence of Reinforcement Types on the
Flexural Properties of Geopolymer Composites,\" Ibid, July 2, 1999.

Hammell, J., Balaguru, P., and Lyon, R., \"High Strength Thin Sheet
Products,\" American Concrete Institute Spring Convention, Chicago,
Illinois, March 1999.

Hammell, J., Balaguru, P., and Lyon, R., \"Use of Ferrocement Theory for
Analysis of High Strength Composites,\" Ferrocement VI, Ann Arbor, MI,
June 1998.

Hammell, J., Balaguru, P., and Lyon, R., \"Behavior of Geopolymer
Reinforced with Various Types of Fabrics,\" SAMPE 1998, Anaheim, CA, May
1998.

Lyon, R., Sorathia, V., Balaguru, P., Foden, A., and Davidovits, J.,
\"New Fire Safe Material for Cabin Interiors,\" AGARD Conference,
Dresden, Germany, October 14-17, 1996.

Foden, A., Balaguru, P., Lyon, R., and Davidovits, J., \"Flexural
Fatigue Properties of an Inorganic Matrix-Carbon Composite,\" SAMPE,
Anaheim, CA, May 1997.

Foden, A., Balaguru, P., and Lyon, R.., \"Mechanical Properties of
Carbon Composites Made Using an Inorganic Polymer,\" ANTEC Symposium,
Indianapolis, IN, May, 1996.

Foden, A., Balaguru, P., and Lyon, R., \"Mechanical Properties and Fire
Response of Geopolymer Structural Composites,\" SAMPE, Anaheim,
California, March, 1996.

Foden, A., Lyon, R., and Balaguru, P., \"High Temperature Inorganic
Resin for Use in Fiber Reinforced Composites,\" First International
Conference on Composites in Infrastructure, NSF, Tucson, Arizona,
January, 1996.

Lyon, R., Sorathia, U., Balaguru, P., and Foden, A., \"Fire Response of
Geopolymer Structural Components,\" First International Conference on
Composites in Infrastructure, NSF, Tucson, Arizona, January, 1996.

Foden, A., Lyon, R., and Balaguru, P., \"Shear Behavior of Fiber
Reinforced Composites Made from High Temperature Inorganic Resin,\" 20th
Annual Conference on Composite Materials and Structures, Florida,
January, 1996.

**ABSTRACT OF THE DISSERTATION**

HIGH STRENGTH-HIGH TEMPERATURE LAMINATED SANDWICH BEAMS

By MOHAMED DA ARAFA

Dissertation Director:

Professor P.N. Balaguru

Structural sandwich panels are commonly used in marine and aerospace
applications. They are composed of a core and skins bonded together
using polymer matrices. Polyvinyl chloride (PVC)/carbon sandwich beams
having organic resins as adhesives are known for their high strength to
weight ratio. One of the major concerns is their vulnerability to fire.
The organic matrices not only deteriorate at temperatures above 300°C
but also emit toxins.

The research presented in this dissertation deals with the development
of PVC/carbon sandwich panels using an inorganic matrix. The matrix can
sustain temperature up to 1000°C and emits no toxins. The primary
objective of the research presented in this dissertation was to evaluate
the feasibility of the matrix for manufacturing sandwich panels. The
evaluation was carried out by fabricating sandwich beams and testing
them in flexure and high temperature fire exposure.

The variables investigated were: foam density, type and volume fraction
of carbon fibers used for skins and extra insulation for fire
protection. Strength, stiffness and high temperature resistance
properties were measured. For temperature resistance evaluation, Ohio
State University test, the NBS test, and heated element exposure test
were used. The results obtained show that inorganic polymer can be
effectively used to fabricate fire resistant sandwich beams. The
strength and stiffness properties of beams fabricated with inorganic
polymer are about -3% and +14% of values obtained for organic polymer
skins. The samples with inorganic polymer skin and 1 mm coating easily
passed the Federal Aviation Administration (FAA) requirements for fire
tests. When exposed to heating element, the beams can sustain 300°C for
indefinite duration and 700°C for 5 minutes. Preliminary studies are
also presented for an all inorganic sandwich beams that can sustain
1050°C. Analytical procedures are presented to estimate the moment
capacities of the beams.

**ABSTRACT OF THE DISSERTATION**

**Influence of Reinforcement Type on the Mechanical Behavior and Fire
Response of Hybrid Composites and Sandwich Structures**

**by JAMES W. GIANCASPRO**

**Dissertation Director:**

**Dr. P.N. Balaguru**

Lightweight composites and structural sandwich panels are commonly used
in marine and aerospace applications. Using carbon, glass, and a host of
other high strength fiber types, a broad range of laminate composites
and sandwich panels can be developed. Hybrid composites can be
constructed by laminating multiple layers of varying fiber types while
sandwich panels are manufactured by laminating rigid fiber facings onto
a lightweight core. However, the lack of fire resistance of the polymers
used for the fabrication remains a very important problem.

The research presented in this dissertation deals with an inorganic
matrix (Geopolymer) that can be used to manufacture laminate composites
and sandwich panels that are resistant up to 1000°C. This dissertation
deals with the influence of fiber type on the mechanical behavior and
the fire response of hybrid composites and sandwich structures
manufactured using this resin. The results are categorized into the
following distinct studies.

\(i\) High strength carbon fibers were combined with low cost E-glass
fibers to obtain hybrid laminate composites that are both economical and
strong. The E-glass fabrics were used as a core while the carbon fibers
were placed on the tension face and on both tension and compression
faces.

\(ii\) Structural sandwich beams were developed by laminating various
types of reinforcement onto the tension and compression faces of balsa
wood cores. The flexural behavior of the beams was then analyzed and
compared to beams reinforced with organic composite. The effect of core
density was evaluated using oak beams reinforced with inorganic
composite.

\(iii\) To measure the fire response, balsa wood sandwich panels were
manufactured using a thin layer of a fire-resistant paste to serve for
fire protection. Seventeen sandwich panels were fabricated and tested to
measure the heat release rates and smoke-generating characteristics.

The results indicate that Geopolymer can be effectively used to
fabricate both high strength composite plates and sandwich panels. A 2
mm thick coating of fireproofing on balsa wood is sufficient to satisfy
FAA fire requirements.

**ABSTRACT OF THE DISSERTATION**

**Evaluation of High Strength Composites and New Construction Techniques
for their Effective Use**

BY MOHAMED NAZIER

Dissertation Director: Dr. P. Balaguru

There is a critical need for new construction materials and construction
techniques for repair and rehabilitation of infrastructures. High
strength fiber composites, known as Fiber Reinforced Polymers (FRP) are
being used for rehabilitation of structures during the past 20 years.
Wet-hand-lay-up is the standard procedure used for attaching high
strength carbon or glass fibers or fiber sheets to concrete, reinforced
concrete and steel structures. Based on the experience of aerospace
industry, vacuum bagging technique that is suitable for repair of
structures in the open construction environment was developed. Extensive
laboratory investigation was conducted to identify suitable
reinforcement, polymer, materials for vacuum bagging including; sealant
tape suitable for concrete placement, vacuum bagging and curing
sequence. This investigation culminated in the field demonstration
project for fabricating a pier cap jacket in an actual bridge in Rhode
Island.

FRP has a number of advantages over the conventional structure materials
but they are the susceptible to fire, UV radiation and the compatibility
of FRP with concrete in terms of permeability and coefficient of thermal
expansion. These shortcomings can be remedied using a recently developed
inorganic polymer. The results presented in this dissertation deals with
the behavior of beams made using bricks and high strength fiber fabrics.
These specimen geometries were chosen to simulate the behavior of brick
walls strengthened with high strength fibers. Feasibility of using the
inorganic polymer for strengthening clay, concrete and hollow core brick
walls, failure mechanism, strength increase, ductility and toughness
were evaluated. An analytical model for predicting the capacity of
strengthened beams is also presented. The inorganic matrix, reinforced
with short fibers was also evaluated for use as a coating material for
concrete structures. The coating provides a protective layer which
provides vapor pressure release. In addition, the coating has a high
hardness and amorphous glassy finish with excellent resistance to
graffiti.

A new failure criterion for estimating the moment capacity of
strengthened reinforced concrete members is proposed. Experimental
investigations conducted all over the world demonstrated that the
maximum carbon fiber strain at failure is always around 0.008 even
though the fracture strain of carbon is 0.015. The criterion proposed in
this dissertation addresses this anomaly. The new criterion provides
reasonably accurate predictions.

> ABSTRACT OF THE DISSERTATION
>
> THE INFLUENCE OF MATRIX COMPOSITION AND REINFORCEMENT
>
> TYPE ON THE PROPERTIES OF POLYSIALATE COMPOSITES
>
> By JAMES A. HAMMELL
>
> Dissertation Director:
>
> Professor P.N. Balaguru
>
> There is a critical need for the development of materials for
> eliminating fire as a
>
> cause of death in aircraft accidents. Currently available composites
> that use organic
>
> matrices not only deteriorate at temperatures above 300ºC but also
> emit toxic fumes.
>
> The results presented in this dissertation focus on the development of
> an inorganic
>
> matrix that does not burn or emit toxic fumes. The matrix, known as
> polysialate, can
>
> withstand temperatures in excess of 1000ºC. The material behaves like
> a ceramic,
>
> but does not need high curing temperatures, so it can be processed
> like many
>
> common organic matrices.
>
> The major parameters evaluated in this dissertation are: (i) Influence
> of
>
> reinforcement type, (ii) Matrix formulation for both wet-dry
> durability and high
>
> temperature resistance, (iii) Influence of processing variables such
> as moisture
>
> reduction and storage, (iv) Tensile strain capacity of modified
> matrices and matrices
>
> reinforced with ceramic micro-fibers and discrete carbon fibers, (v)
> Analytical
>
> modeling of mechanical properties.
>
> ii
>
> For the reinforcement type; carbon, glass, and stainless steel wire
> fabrics were
>
> investigated. Carbon fabrics with 1, 3, 12, and 50 k tows were used. A
>
> matrix chemical formulation that can withstand wetting and drying was
> developed.
>
> This formulation was tested at high temperatures to ascertain its
> stability above
>
> 400ºC. On the topic of processing, shelf life of prepregged fabric
> layers and efficient
>
> moisture removal methods were studied. An analytical model based on
> layered
>
> reinforcement was developed for analyzing flexural specimens.
>
> It is shown that the new inorganic matrix can withstand wetting and
> drying, and also
>
> high temperature. The layered reinforcement concept provides accurate
> prediction
>
> of strength and stiffness for composites reinforced with 1k and 3k
> tows. The pre-
>
> pregged fabric layers can be stored for 14 days at -15ºC without
> losing strength.

# ABSTRACT OF THE DISSERTATION

Mechanical Properties and Material Characterization

of Polysialate Structural Composites

by Andrew J. Foden

Dissertation Director:

Professor P.N. Balaguru

> One of the major concerns in using Fiber Reinforced Composites in
> applications that are subjected to fire is their resistance to high
> temperature. Some of the fabrics used in FRC, such as carbon, are

fire resistant. However, almost all the resins used cannot withstand
temperatures higher than 200°C.

This dissertation deals with the development and use of a potassium
aluminosilicate (GEOPOLYMER)

resin that is inorganic and can sustain more than 1000°C.

The results presented include the mechanical properties of the
unreinforced polysialate matrix in

tension and compression as well as the strain capacities and surface
energy. The mechanical

properties of the matrix reinforced with several different fabrics were
obtained in flexure,

tension, compression and shear. The strength and stiffness of the
composite was evaluated for

each loading condition. Tests were conducted on unexposed samples as
well as samples exposed

to temperatures from 200 to 1000°C. Fatigue properties were determined
using flexural loading.

A study of the effect of several processing variables on the properties
of the composite was under-

taken to determine the optimum procedure for manufacturing composite
plates. The processing

variables studied were the curing temperature and pressure, and the post
cure drying time required

to remove any residual water. The optimum manufacturing conditions were
determined using the

void content, density, fiber volume fraction, and flexural strength.

> Analytical models are presented based on both micro and macro
> mechanical analysis of the

composite. Classic laminate theory is used to evaluate the state of the
composite as it is being

> loaded to determine the failure mechanisms. Several failure criteria
> theories are considered. The
>
> analysis is then used to explain the mechanical behavior of the
> composite that
>
> was observed during the experimental study.

**ABSTRACT OF THE THESIS**

HIGH TEMPERATURE/ HIGH STRENGTH DISCRETE FIBER

REINFORCED COMPOSITES

By CHRISTIAN F. DEFAZIO

Thesis Director:

Dr. P.N. Balaguru

Most of the high temperature resistant composites are made using ceramic
matrices. Typically these composites are processed at temperatures
higher than the operating temperatures. The results presented in this
thesis focus on the development of an inorganic matrix composite that
can be processed at temperatures ranging from 80 to

400ºC and can withstand temperatures up to 1500ºC. The composites can be
fabricated using inexpensive mold-cast techniques or vacuum bagging
techniques. Short discrete fibers can be incorporated in the matrix to
improve mechanical properties.

The composite is a two component system consisting of: potassium/ sodium
silicate solution and a powder component containing; silica, alumina,
fillers, fibers, flow enhancing additives and activators. The major
parameters evaluated in this dissertation are: (i) influence of fiber
type and fiber content, (ii) matrix composition in terms of
silica/alumina ratio, (iii) fabrication techniques, (iv) influence of
curing temperature and (v) influence of exposure to temperatures varying
from 200 to 1500ºC. The response variables were: the integrity of the
samples after high temperature exposure and the mechanical property of
the composite. The fiber types consisted of: economical bulk alumina
fibers, alumina fibers in paper form and uniform-short alumina fibers.
The fiber content varied from 4 to 13 percent by weight of total matrix.
Silica to alumina ratios were varied from 1 to 5. Fabrication techniques
investigated include: compression molding using wetted alumina fiber
papers and simple casting using a mold and vacuum bagging technique.

The major findings are as follows:

• Both mold-casting and vacuum bagging techniques can be effectively
used for fabrication

• Optimum curing temperature is 400ºC

• For composites with bulk-economical alumina fibers the maximum
flexural strength is 65 Mpa and the maximum flexural modulus is 52 GPa

• These values can be increased to 130 MPa and 85 GPa by using high
quality fibers

• The densities for composites with short fibers range from 2000 to 2800
kg/m3

• Typically higher density leads to higher strengths

AN INVESTIGATION OF THE USE OF BIOMASS WASTE PRODUCTS FOR CREATING
INORGANIC POLYMER COMPOSITES, AND THE INFLUENCE OF REINFORCEMENT ON THE
MECHANICAL BEHAVIOR AND FIRE RESPONSE OF SANDWICH STRUCTURES

by

PHILIP JOHN-JUDE FELTZ

**Abstract**

Recently, the rising cost of construction materials has made it
necessary to investigate the possibility of developing alternate
building materials from industrial byproducts. One material that has
shown promise in this function is Geopolymer, an inorganic polymer resin
that exhibits the ability to produce enhanced structural stability while
maintaining high heat and fire resistance simultaneously. When combined
with industrial byproducts such as sawdust and rice husk, viable
alternate construction materials may be produced. This paper focuses on
the steps taken to create these new materials, and discusses the
performance of Geopolymer-sawdust composites in mechanical and fire
testing, and discusses the performance of Geopolymer-husk composites in
mechanical testing. The results obtained and analyzed show that promise
exists to further investigate the development of these

**Conclusions and Suggestions for Further Research**

**Foden**

## Conclusions

A careful review of the experimental and analytical results obtained
during the

investigation lead to the following conclusions:

▪ Polysialate structural composites have an excellent potential for use
in applications

where exposure to high temperatures or fire is a concern. It is
anticipated that the load

bearing capability of GEOPOLYMER during severe fire exposure, where
temperatures

reach several hundred degrees Centigrade, will be significantly higher
than organic

resin composites, steel, and aluminum which will soften and lose nearly
all of their

compressive strength well below these temperatures. Hence the material
has excellent

potential for various types of applications including: aircraft, naval
structures,

automobiles, and infrastructures.

▪ The polysialate marix slows the oxidation of carbon fibers at
temperatures up to

1000°C.

▪ The stress-strain response of the neat resin is linear elastic in
tension and compression.

In all cases the failure was brittle and post peak resistance is
negligible.

▪ The compressive and tensile strengths of the neat resin were 39 MPa
and 3.7 MPa

respectively.

▪ The compressive and tensile strain capacities of the neat resin were
5173 10^6^ mm/mm

and 743 x 10^6^ mm/mm respectively.

▪ The flexure strength and strain capacity of the neat resin were 9.4
MPa and 860 x 10^6^

mm/mm respectively.

▪ The surface energy of the neat resin which is 1.653 Joules/m^2^ is
nearly identical to that

of glass.

▪ Optimum plate properties for polysialate/carbon composite plates can
be obtained by

curing at 80ºC under a pressure of 3 MPa and post-processing at 80ºC for
a minimum

of 12 hours to remove residual moisture.

▪ The flexural strength of 245 MPa is comparable to that obtained for
organic matrix

composites. The load capacity drops only 37% if the specimen is exposed
to 800ºC

for one hour.

▪ The interlaminar shear strength of 14 MPa drops to 12.5, 6.8, 4.6,
4.6, and 5.6 MPa

after a one hour exposure at temperatures of 200, 400, 600, 800, and
1000ºC

respectively, indicating that the composite can sustain in-plane shear
of 4.6 MPa at

very high temperatures.

▪ The in-plane shear strength of 30.5 MPa and shear modulus of 4.03 GPa
is comparable

to those of organic matrix composites.

▪ The tensile strength of the polysialate/carbon composite is comparable
to those of

similarly reinforced organic matrix composites at room temperature and
exceeds those

of the organic matrix composites after a temperature exposure of 600ºC.

▪ The compressive strength of the polysialate/carbon composites is
significantly less

than that of organic matrix composites due to the premature tensile
splitting failure

mode.

▪ The performance of the carbon-Geopolymer composite under fatigue
loading is similar

to that of other structural materials. The S-N curve has three segments
with a linear

portion in the failure cycle range between 10,000 and 500,000 cycles.

▪ The composite can sustain about 10 million cycles at a stress range of
40% and a

minimum stress range of 10%, which gives a mean stress value of 30%.

▪ The deflection at maximum load increases with increasing number of
cycles. The

> increase is significant for samples that sustain more than 1 million
> cycles. The
>
> increase in deflection seems to occur due to permanent cyclic-creep
> deformation
>
> rather than a decrease in the flexural stiffness. The difference in
> deflection between

maximum and minimum load does not change significantly with an increased
number

of cycles, indicating the stiffness of the beam does not decrease under
cyclic loading.

▪ A strength of materials based micromechanical model provides excellent
predictions

of the elastic moduli of the polysialate/carbon composite.

▪ Classical lamination theory shows that the mode of failure during
flexural loading is

due to the matrix strain capacity being exceeded in the outermost
compression fibers

leading to buckling of the carbon fiber reinforcement.

▪ The knee behavior observed during the tension tests of the
polysialate/carbon

composites is due to the transverse cracking around the warp threads as
the strain

capacity of the matrix is exceeded in the highest strain region. This
leads to a

softening in the elastic modulus. Once all the warp regions have failed
the

stress/strain behavior again becomes linear up until failure.

## Suggestions for Further Research 

**▪** A room temperature setting matrix needs to be developed for
infrastructure

applications where it is not practical to apply the curing temperatures
required for the

present matrix.

▪ Investigation of other more economical reinforcements such as glass
fibers should be

conducted for applications where achieving high structural loadings is
not imperative.

▪ A fiber sizing that is compatible with the polysialate resin needs to
be developed to

take full advantage of the mechanical properties that can be obtained
with this

composite system.

**Hammell**

**Conclusions**

# CONCLUSIONS AND SUGGESTIONS FOR FUTURE RESEARCH

## Conclusions

Polysialates are promising materials for use in high strength composites
that require

resistance to fire and high temperatures. The results presented in this
dissertation

focus on: (i) Influence of reinforcement type, (ii) Matrix formulation
for both wet-

dry durability and high temperature resistance, (iii) Influence of
processing

variables such as moisture reduction and storage, (iv) Tensile strain
capacity of

modified matrices and matrices reinforced with ceramic microfibers and
discrete

carbon fibers, and (v) analytical modeling of mechanical properties. The
major

findings are presented as conclusions in the following sections.

### Influence of Reinforcement Type 

▪ As expected, carbon fibers provided the maximum stiffness and flexural

strength. Strengths as high as 510 MPa can be achieved using
unidirectional

carbon fabric.

▪ E-Glass fibers fused with the matrix, providing a linear elastic
behavior up to

failure. Curing at 80ºC, in the high alkali matrix degraded the glass
fiber

resulting in a low flexural strength of 100 MPa.

▪ Steel wire meshes produced high initial moduli, but failure was
initiated by

yielding . Since the yielding occurs at a strain of 0.002 mm/mm, the
strengths

are limited to 140 MPa. However, yielding provides a much more ductile

behavior which is useful in certain applications such as impact
resistance.

▪ Combinations of carbon and e-glass fibers can be used to achieve the
strength as

samples of carbon fibers. Almost 50 percent of the carbon fibers can be
replaced

with more economical fibers, with little effect on strength.

▪ As tow size increases, the contribution of the carbon fiber to the
composite

strength decreases. The decrease occurs because of buckling of tows in
the

compression region.

### 

### 

### Wet-Dry Resistance and Thermomechanical Durability

▪ Polysialate matrices with a silica/alumina ratio of 27 are susceptible
to

degradation under wet-dry cycling. The performance can be improved by
raising

the curing temperature from 80ºC to 150ºC.

▪ Reduction in the silica/alumina ratio results in a durable matrix
under wetting and

drying conditions. At a silica/alumina ratio of 18.6, the matrix
strength increased

by 6% while the sample was being exposed to wet/dry cycling.

▪ The use of a silicone based water repellent had a synergistic effect
with the

reduced silica/alumina ratio. However, the water repellent alone was not

sufficient to improve matrix water stability.

▪ The thermomechanical durability of the composites was unaffected by
the

reduction in silica/alumina ratio. The composite maintained 53.5% of its
original

flexural strength and 30.1% of its original flexural modulus after
exposure to

600ºC for 1 hour.

### 

### 

### Processing Variables

▪ The optimal curing temperature with respect to strength, durability
and economy

was found to be 150ºC. Strength values decreased when the samples were
cured

to 200ºC. It is suspected that both sizing and carbon fiber experience
chemical

changes at 200ºC.

▪ The hand impregnation process was found to be consistent, with
coefficients of

variation of approximately 5-6%.

▪ Extra water can be removed from the matrix by drying impregnated
fabric layers

or by drying the surface of the composite after each lamina is added.

▪ Fabric sizing is necessary to prevent fiber damage during impregnation
and

composite fabrication. Removal of sizing by heating the fabric layers to
200ºC

resulted in poor performance.

▪ The alumina additive must have a sufficiently small particle size in
order to

effectively wet-out the carbon fiber. Strengths reduced considerably
when the

95^th^ percentile particle size was greater than or equal to 7μm, which
is the carbon

fiber diameter.

▪ The pre-pregged fabric layers can be stored at low temperature (-15ºC)
for 14

days without any strength loss. In fact, flexural strengths increased
slightly

during that time.

▪ The storage time had no effect on the thermomechanical properties of
the

composite.

▪ Room temperature storage of the pre-pregged fabric layers is not
viable.

Significant strength reduction occurred in less than 2 days.

### Tensile Strain Capacity of Polysialates

▪ Tensile strain capacity of the matrix was relatively unaffected by the
reduction of

the silica/alumina ratio. Inclusion of a small amount of discrete carbon
fibers

slightly increased the cracking strain through fiber bridging
mechanisms.

▪ The inclusion of 10% microfibers significantly increased the cracking
strain.

However, viscosity was also dramatically increased, so use of this
matrix in a

fiber composite is not feasible.

### Analytical Modeling

▪ Application of the layered reinforcement concept provides a successful
model

for the analysis of inorganic matrix composites. The model provides
accurate

predictions of strength and stiffness for unidirectional fabrics and
woven fabrics

with 1k and 3k tows. For fabrics made with larger tows, an equivalent
modulus

that accounts for fabric tow undulation is needed.

▪ The model allows for the incorporation of yielding of steel and
accurate

performance prediction for steel/e-glass inorganic matrix composites.

### Recommendations for Further Research

▪ The fabrication method needs to be automated for consistency. Methods

common to the organic matrix composite industry such as Resin Transfer

Molding and autoclaving should be investigated.

▪ An effective method of removing free water from the matrix during
curing must

be developed. This will allow sample thicknesses to increase without
large

blisters forming at mid-plane.

▪ The shrinkage of the matrix needs to be controlled, possibly in the
same manner

that Type K cement compensates for shrinkage. Many of the problems with

mechanical strength are the result of stresses caused by matrix
shrinkage.

▪ Fabric sizings that will provide post-cracked strength in e-glass
fabric should be

investigated.

▪ Develop room temperature setting polysialates that can be used in
composite

materials for civil infrastructure applications.

**Nazier**

**Conclusions**

The results presented in this dissertation can be divided into five
focus areas dealing with: (i) State of the art on the utilization of
Fiber Reinforced Polymers (FRP) for protection, repair and
rehabilitation concrete structures, (ii) Development of inorganic
polymer-high strength fiber composites for strengthening of unreinforced
masonry structures, (iii) A new construction technique using "vacuum
bagging" for attaching high strength fibers (fabrics) to concrete
structural elements, (iv) Fiber reinforced inorganic polymer coatings
for protection and graffiti resistance of exposed concrete structural
elements and (v) A new criterion for providing the moment capacity of
reinforced concrete beams strengthened with FRP. The conclusions derived
from these evaluations, presented in the following sections, are grouped
into the aforementioned focus areas.

**Review of the State- of -- the - Art**

-   Fiber Reinforced Polymers (FRP) is a feasible and cost effective
    alternative structural material for rehabilitation of
    infrastructure.

-   The major disadvantage of organic polymer FRP is its vulnerability
    to fire.

-   Both inorganic and organic matrices provide good initial bond to
    concrete surfaces.

-   As compared to organic matrix, inorganic matrix has advantages in
    the areas of UV light resistance and vapor pressure release.

-   In the case of beams strengthened with organic polymer, the common
    failure is due to delamination of the composite plate.

-   As a consequence, the allowable maximum stress in composite
    decreases with the increase in the thickness of the repair
    (composite) layer.

-   In the case of beams strengthened with inorganic polymer, the common
    failure mode is by fracture of fibers.

**Inorganic Polymer Composite for In Plane Strengthening of Brick
Walls**

Brick triplets were used in this study to simulate the retrofitting of
unreinforced masonry walls reinforced with inorganic polymers FRP. The
results of this investigation lead to the following conclusions:

-   For both clay and concrete brick types, the standard mortar provides
    the same strength for control samples.

-   Inorganic matrix can be used to strengthen both clay and concrete
    brick masonry. The matrix and the composite have an added advantage
    of fire protection.

-   The strength increases provided by inorganic matrix are about the
    same as the increases provided by organic matrix.

-   Aramid fibers provide more ductility than carbon fibers. However,
    much larger fiber area is needed to provide the same strength
    increase.

-   The strength increases provided by carbon reinforcement depends on
    the mortar strength. Stronger mortar results in much larger strength
    increases for reinforced samples.

-   The results indicate that it is feasible to use carbon fabric tape
    grids to increase the shear strengths of brick walls.

**Inorganic Polymer Composites for Out -- of - Plane Strengthening of
Brick Walls**

Two sets of masonry beams retrofitted with FRP were investigated. The
beams were tested to simulate the flexure behavior of unreinforced
masonry walls retrofitted with FRP. The following are the conclusions:

-   It is feasible to strengthen unreinforced masonry walls using carbon
    and inorganic matrix. The matrix bonds well to the surface as
    indicated by the fact that none of the failures occurred due to
    delamination.

-   Consistent increases in carbon area provide consistent increase in
    strength, flexural strength and toughness. Nevertheless, there is a
    limit for the optimum area of fabric to be used, after which
    increasing the area of fabric will not be effective.

-   Carbon fabrics are more effective than carbon tows. The author
    believes that in the case of fabrics a much larger fraction of
    fibers are perfectly oriented on the loading direction.

-   Carbon fiber reinforcement is much more effective than glass fiber
    reinforcement.

-   Inorganic and organic matrices give almost the same increase in load
    capacity of the reinforced beams.

**Vacuum Bagging Technique for Strengthening with FRP**

Laboratory investigation conducted to develop vacuum bagging technique
and field demonstration project in Rhode Island lead to the following
conclusions:

-   Application of Glass FRP to retrofit damaged concrete surfaces of
    existing pier caps is feasible. It is possible to create and
    maintain vacuum on the primed concrete surface.

-   Vacuuming technique helps strengthen the bond between the fibers and
    the retrofitted concrete surface. This is accomplished by releasing
    the micro air bubbles at the interface between the fabric and the
    parent surface.

-   The matrix and the fiber have to be selected carefully for every
    application. The pot life and the vacuuming period have to be
    adequate to achieve proper application and curing.

-   The vacuuming technique helps follow the contours of irregular
    surfaces.

-   The vacuum pumps of the parent structural elements have to be of
    adequate capacity and the permeability of the concrete has to be
    taken into consideration.

-   The concrete surface has to be carefully treated and has to be free
    from any lose particles.

The pier caps are still under monitoring phase. Periodical chloride
samples will be taken to evaluate the rate of water penetration to the
pier caps. A digitalized monitoring system is being developed to
evaluate the deterioration of the FRP layer. Finally, a pull out test
will be used as final evaluation for the used technique.

**Fiber Reinforced Inorganic Polymer and Protective Coatings**

Inorganic polymer with concrete color pigments were used as a protective
coating for concrete surfaces. The experimental program along with the
field application lead to the following conclusions:

-   The inorganic coating is resistant to UV light, releases vapor
    pressure and is fire resistant.

-   The inorganic coating is compatible with carbon, glass and Aramid
    fibers.

-   The inorganic coating is durable under scaling, wet-dry and
    freeze-thaw conditions.

-   The inorganic coating is compatible with color pigments used in
    concrete. By applying the right mix of pigments, one can obtain
    almost any desired color which can be used for both protection and
    decoration.

-   The inorganic coating is easy to apply and does not need complicated
    preparations, neither for the matrix or the coated surface.

-   The inorganic coating is resistant to graffiti.

**Analytical Model for Computing Moment Capacity of FRP Strengthened
Reinforced Concrete Beams**

A new analytical model was developed for the calculation of the moment
capacity of reinforced concrete beams externally strengthened with FRP.
Comparing experimental results to the analytical results lead to the
following conclusions:

-   The analytical model predicts the moment capacity of the reinforced
    beams with a good accuracy, even though the experimental results
    used were taken from existing literature reported by a number of
    investigations around the world.

-   The model is sensitive to the orientation of the fibers. As the
    orientation of the fibers will reflect on the amount of area
    utilized.

-   A new paradigm is needed to utilize the full strain (and strength)
    capacity of carbon fibers. The instability created by yielding and
    hardening of mild steel need to be addressed.

Giancaspro

Conclusions

This dissertation examines how the type of reinforcement influences the
behavior of hybrid composites. The literature review, presented in
Chapter 2, provides information on the components, types, and
applications of hybrid composites. Common types and forms of fiber
reinforcement materials, various kinds of commercially available resins,
and background information on Geopolymer are presented in this chapter.
The four basic types of hybrids are discussed with a more detailed
summary of sandwich structures, including the various core types and
typical configurations. Periodically throughout the literature review,
the applications of hybrid composites are illustrated.

Chapter 3 presents the characteristics of the fibers and fabrics used to
reinforce the samples for this dissertation. Each form of reinforcement
was evaluated on several different criteria. Consideration of these
results yields the following conclusions.

-   The predominant factors in determining wet-out of the reinforcement
    were the fiber type and the amount of sizing placed on the fibers by
    the manufacturer. In many cases, the fiber sizing interfered with
    the proper wet-out of the fibers with the Geopolymer resin. More
    than 1% sizing is not recommended.

-   Increased modulus makes the fibers stiffer and, consequently, easier
    to handle prior to resin impregnation. This was particularly evident
    when using the 12k High Modulus Carbon (HMC) tows.

-   Heavier fabrics were much easier to handle than thin fabrics since
    they are not prone to folding and adhering to themselves once wet
    with resin. However, as the fabric weight increased, more effort was
    required to both cut and impregnate the fibers.

-   As the tow size increased, the porosity of the fabric decreased.

-   In terms of cost, carbon fibers and fabrics with small tow sizes
    were most expensive.

The mechanics and logistics of the manufacturing methods used to
fabricate the laminate samples are presented in Chapter 4. These methods
included resin mixing, hand lay-up technique, and vacuum bagging. In
addition, curing methods, density determination, and laminate cutting
are also described. A number of processing factors such as curing
pressure, curing temperature, and refrigeration were investigated. This
study indicated that the flexural strength of laminate composites is
influenced by the processing.

-   The maximum flexural strength of E-glass / Geopolymer composites
    occurred at a curing pressure of approximately 1 MPa. Using a
    pressure higher or lower than 1 MPa resulted in a weaker composite.
    Similarly, the ideal curing pressure for carbon composites was
    determined to be 3 MPa.

-   For E-glass composites, as the curing temperature increases, the
    flexural strength of the composite decreases.

-   Without any refrigeration, the flexural strength of the E-glass
    composite was approximately 84 MPa. Refrigerating the Geopolymer
    resin for 15 minutes prior to lay-up resulted in an increase in
    strength to 113 MPa. Using constant refrigeration during the entire
    manufacturing process led to a flexural strength of 122 MPa.

The study on the properties of tensile specimens obtained from witness
panels yielded a number of conclusions regarding the statistical
variation of strength and specimen dimensions. The average coefficient
of variation for composite strength was 11.1%. Performing a similar
calculation for the width values, it was determined that the average
coefficient of variation was approximately 4.5%. For the bridge
rehabilitation project in Rhode Island, the coefficients of variation
for strength and width were 12.4% and 1.3%, respectively, which
indicates that the amount of variation was about the same as in other
bridge projects.

An extensive investigation of the tensile properties of Geopolymer
composites consisted of 82 specimens made using 17 different
configurations of fibers, fabrics, and number of plies. Based on the
test results, the following conclusions were reached.

-   Unlike carbon and Kevlar^®^ composites, which retained a
    considerable load after the initial fracture, the brittle E-glass
    composite failed completely into two or more distinct pieces, with
    no post-peak strength. It is believed that the Geopolymer resin
    fuses with the E-glass fiber, resulting in a very brittle composite.

-   Nearly all of the carbon composite specimens failed with a
    longitudinal splitting type of failure.

-   As expected, the 12k high modulus carbon tows exhibited the highest
    modulus of elasticity, namely, 576 GPa.

-   The fiber undulation of woven fabrics is believed to have reduced
    the modulus of elasticity of the tensile specimens.

-   The average strains at peak load for the Kevlar^®^ samples were
    nearly 20 times the strain at peak load for the high modulus carbon.
    Although the Kevlar^®^ samples can be considered less stiff, they
    can absorb more energy before fracture. In general, the average
    strains at peak load were lowest for the high modulus carbon,
    followed by E-glass, high strength (normal modulus) carbon, and
    Kevlar^®^.

-   The highest composite strength for the Geopolymer specimens was
    exhibited by the specimens fabricated using the 3k Unidirectional
    Carbon fabric with the heated curing method, 602 MPa (87.3 ksi).

-   Three sets of samples were used to determine whether size effect was
    present for the Geopolymer tensile specimens. Samples made from
    E-glass, 3k unidirectional carbon (room temp. curing), and 3k
    unidirectional carbon (heated curing) indicated that composite
    tensile strength is not dependent upon the size (number of plies) of
    the specimen.

-   The heated curing method leads to a better quality specimen and a
    stronger composite. For samples utilizing 3k unidirectional carbon
    fabric, the heated curing fabrication technique led to nearly 3
    times the fiber content than that of the room temperature curing
    technique. Furthermore, the heat cured composite was 34% stronger
    than the samples cured at room temperature.

-   In terms of statistical variation, the average coefficient of
    variation of specimen width for the entire Geopolymer investigation
    was approximately 0.5%, far lower than the 4.5% found in the bridge
    rehabilitation witness panels. The variation found in the composite
    strength per ply was 11.9% for the Geopolymer set, nearly equal to
    the 11.1% for the witness panels.

For the laminate composites made from a single fiber type, the highest
flexural strength was exhibited by the 3k unidirectional carbon, 466
MPa, followed by the "3k Woven Carbon & Glass" composite, 429 MPa. As
the tow size of the fabric increased, flexural strength and stiffness
both decreased. Using the analysis of the results and observations made
during the fabrication and testing of the hybrid laminates, the
following conclusions can be drawn.

-   When E-glass is reinforced with carbon fabric on the tension side,
    the strength increases. For each fabric type, two layers of carbon
    on the tension side provide the highest strength. Placing carbon
    layers on both compression and tension faces does not appear to
    provide significant strength improvement as compared to carbon on
    the tension side alone.

-   E-glass plates reinforced with 1, 2, or 3 layers of carbon exhibited
    the highest strength when the fabric was 3k unidirectional. Slightly
    lower strengths were achieved using the 3k woven carbon / glass
    fabric while the lowest strengths were obtained using 1k woven
    fabric.

-   The uncracked section modulus for E-glass reinforced with 1k or 3k
    woven on the tension side showed little change as the number of
    layers increased. However, 3k unidirectional carbon on the tension
    side provided a modulus increase with an increasing number of
    layers. This is also true for carbon on both the compression and
    tension sides.

-   When using Kevlar^®^ skins on an E-glass core, the addition of one
    layer of fabric resulted in a 150% increase in flexural strength
    compared to samples made entirely from E-glass or Kevlar^®^. Two
    layers on the tension face provided an increase of approximately
    160%, while three layers resulted in an increase of more than 200%.

-   It is feasible to fabricate inorganic / organic matrix hybrid
    plates. All carbon samples manufactured using the Epondex^®^ resin
    system and inorganic glass skins failed as the skins delaminated
    from the organic core. In the five samples where compressive
    buckling occurred, the glass skins remained intact as an integral
    part of the plate.

-   The inorganic glass layer is very brittle and contributes very
    little to strength of matrix hybrids.

Consideration of the results presented in the sandwich beam studies and
observations made during fabrication and testing, the following
conclusions can be drawn regarding the beams reinforced with the
inorganic composite.

-   It is feasible to fabricate sandwich panels using a balsa core and
    inorganic matrix-carbon composite. The bond between the inorganic
    carbon composite and the balsa wood is strong enough to prevent
    delamination.

-   Increase in carbon area provides consistent increase in moment
    capacity. The magnitude of strength increase is proportional to
    carbon area.

-   At low reinforcement (carbon area) ratios, the failure occurs by
    fracture of carbon. When the reinforcement ratio is increased beyond
    0.75%, failure occurs at the compression region.

-   High modulus carbon fibers provide better strength increase than
    normal modulus carbon fibers.

-   Increase in fiber area provides consistent increase in flexural
    stiffness. Even a small carbon volume fraction provides substantial
    increase in stiffness.

-   The energy or toughness increased as the reinforcement ratio
    increased. In general, beams reinforced with tapes (normal modulus
    fibers) exhibited the largest toughness.

By comparing similar beams reinforced using the organic epoxy, the
following conclusions can be reached.

-   The thickness of the organic resin layer plays an important role in
    determining the failure mechanism of the beam. In the inorganic
    system, the resin layer does not play a role in the failure
    mechanism. The bond between the balsa wood and the organic
    reinforcement is poor, as several delamination-type failures
    occurred.

-   On the average, the beams reinforced with organic reinforcement
    provided approximately 70% more moment capacity than those
    reinforced with the inorganic resin.

-   In terms of stiffness, the organic epoxy showed no distinct
    advantage over the inorganic resin.

-   The toughness values of the organic reinforced beams were
    significantly higher than the beams with inorganic reinforcement.

Investigating the effect of core density on the flexural behavior of the
sandwich beams yielded the following important conclusions.

-   It is feasible to fabricate sandwich panels using balsa or oak cores
    and inorganic matrix composite. The bond between the inorganic
    carbon composite and both types of wood cores is strong enough to
    prevent delamination.

-   All of the oak beams failed with a brittle fracture on the tension
    side of the beam, regardless of the amount, type, or location of
    reinforcement. As the density reduces, the shear stiffness plays a
    major role in the failure mechanism.

-   The reinforced balsa beams displayed significantly higher increases
    in stiffness and toughness than the strengthened oak beams.

-   The flexural strength of the plain wood cores is strongly related to
    density and the strength can be predicted accurately using a simple
    linear regression model.

-   There is no linear relationship between maximum capacity and density
    for strengthened beams. Similarly, a linear relationship does not
    exist between deflection at maximum load and density for the
    strengthened beams.

-   Based upon observations made while examining the bond depths of the
    sandwich beams, it appears that the Geopolymer is compatible with
    and has an affinity for cellulose materials such as wood.

Using the analysis of the results presented in Chapter 8 and
observations made during fabrication and testing, the following
conclusions can be drawn regarding the fire response of balsa sandwich
panels.

-   It is feasible to fabricate economical sandwich panels using balsa
    cores and inorganic matrix composite. In addition, a layer of
    fireproofing with a controlled thickness can be applied with ease.

-   As the thickness of the fireproofing layer increased, its influence
    on the mass distribution of the sandwich composite also increased.

-   A 2 mm thick layer of fireproofing is sufficient in providing
    adequate heat release protection and easily satisfies the FAA smoke
    requirements, while increasing the mass of the sandwich plate by 8%.
    Samples with a fireproofing layer thicker than 2 mm can be utilized
    in more rigorous fire applications that are less weight critical.

-   It appears that the type of reinforcement on the facings plays a
    significant role in determining the amount of smoke generated.
    Fabrics with only carbon fiber generate much less smoke than the
    fabrics that had glass fibers in the fill direction

-   A strong relationship exists between the thickness of the
    fireproofing and the sandwich plate density. For any given thickness
    of fireproofing, the resulting density of the sandwich structure can
    be estimated accurately.

The proposed analytical procedures, which are based on simple principles
of mechanics and the law of mixtures, lead to the following conclusions.

-   Both the cracking moment and maximum moment capacities can be
    predicted with good accuracy using the ferrocement-based model. The
    critical factors are uniform distribution of fibers and the modulus
    of elasticity of fibers.

-   Both experimental and analytical results indicate that a much
    stiffer glass / carbon hybrid composite can be created by placing
    carbon reinforcement on both the compression and tension faces of
    the glass core.

-   The glass / carbon hybrid model provides reasonably accurate
    predictions for stiffness of the uncracked section. The model
    yielded excellent results for composites made using a single fiber
    type (non-hybrid) while the moment capacity and failure mode of the
    hybrid composites can be predicted with very good accuracy.

Arafa

**Conclusions**

The results presented in this dissertation focus on the evaluation of
sandwich beams made using polyvinyl chloride (PVC) foam and inorganic
facings as reinforcement. The literature review, presented in chapter 2,
provides information on the various materials used for cores, facings
and resins, sandwich panel commonly available configurations, a brief
description of the analytical models available, and a detailed
description of the evolution of Geopolymer research at Rutgers, the
State University of New Jersey.

The results of the state-of-the art indicate that while considerable
progress is made on the development of lightweight sandwich structural
elements with excellent mechanical properties, there is a critical need
for the development of fire resistant sandwich structures. Development
of fire resistant panels is a prerequisite for increasing their use in
aerospace and naval structures. Fire resistance will also promote the
use of the system in general building construction and automobile
structures.

Chapter 3 presents the results of the experimental study on the
mechanical properties of sandwich beams having PVC core and
carbon/Geopolymer facings. Based on observations made during fabrication
and tests, test results presented in chapter 3 and their analysis lead
to the following conclusions.

1.  • It is feasible to fabricate sandwich panels using PVC core and
    carbon/Geopolymer composites. Excellent bond could be achieved
    between the inorganic resin and the PVC core, the bond is strong
    enough to eliminate skin delamination.

    • The lighter cores tend to absorb more resin than the more dense
    ones, which provides better adhesion but this may affect its
    specific strength, and could be critical in applications where the
    total weight is a design parameter. The weight increase for the
    lighter foams is in the range of 234% to 473% where as the
    corresponding percentages for denser foams are 36% to 54%.

    • Since the specimens were fabricated using hand-laying process,
    increase in fiber content seems to result in increase of fiber
    damage. Therefore, three fold increase in reinforcement provides
    only two fold increase in moment capacity.

    • Increase in core density provides consistent increase in moment
    capacity.

    • Increase in flexural stiffness with the increase of carbon fiber
    area is consistent with improvements in moment capacity.

    • The denser the core is the higher stiffness that could be
    attained. The increase in density from 50 Kg/m^3^ to 250 Kg/m^3^
    provides an average increase in the stiffness of 180%.

    • Compression failure is more prevalent for low density cores.

    • N-12K MMC (440 GPa modulus) fibers provide higher moment capacity
    than H-12K HMC (640 GPa modulus fibers) even though it has lower
    modulus.

    • Most failures are initiated by crimping of compression
    reinforcement. But increasing compression reinforcement does not
    increase moment capacity or stiffness significantly.

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1.  • The toughness increases as the reinforcement area increases. Beams
    reinforced with N-12K MMC fibers provide higher toughness than the
    ones reinforced with H-12K HMC. On the whole, beams reinforced with
    carbon tape exhibited the largest toughness.

    • Beams reinforced with organic polymer composites are 10% lighter
    and the additional weight per tow is 40% less than the corresponding
    beams reinforced with inorganic resin.

    • The organic polymer composites provide only 3% higher moment
    capacity than those reinforced with inorganic polymer composites.

    • The stiffness for inorganic polymer composites is 14% higher than
    the organic polymer composites.

    • Organic composites provide higher ductility than beams with
    inorganic polymers.

    • The failure in the skin occurs at a fraction of the ultimate
    strength of the fibers (53%), in other words, the skin is not fully
    stressed at failure. The maximum moments are controlled by bearing
    stresses or compression buckling of the skin.

    • Without skin and 36% more dense, the balsa control beams have
    2000% more moment capacity and 2750% more stiffness than PVC control
    beams.

    • For reinforced beams, the balsa beams have an average of 170% more
    moment capacity and 230% more stiffness. The difference decreases
    with the increase of the reinforcement ratio.

    • The long grain balsa sandwich beams have higher mechanical
    properties but their use is only limited to one dimensional elements
    (beams). However, the Polyvinyl (PVC)

sandwich beams can be used in fabricating two dimensional elements
(plates and shells).

The analytical model presented in chapter 4, which takes into account
the vertical stress field imposed from the indentation stresses, leads
to the following conclusions.

1.  • Most of the failures are triggered by compression in the core.

    • Indentation stresses can not be neglected in applications
    involving concentrated or contact loads.

    • The effect of indentation stresses increases with the increase of
    the depth to span ratio.

    • As expected, the effect of indentation stresses has more influence
    in cores with lighter density.

    • Based on the failure hypothesis and its verification, the load
    deflection deviates from linearity when the core yields, and the
    ultimate load corresponds to the ultimate capacity of the PVC core.

    • In typical cases, the ultimate stress of fibers can not be
    attained, if the concentrated are present. The failure will occur
    due to indentation. Special details may be used to increase the
    fiber stresses at failure.

    • The ultimate load approaches the lower bound solution with the
    increase of density and the increase of reinforcement ratio.

> The proposed optimum design method presented in chapter 5, leads to
> the following conclusions:

1.  • The PVC/carbon sandwich beams can be optimized for weight for a
    required stiffness.

    • Design aids and charts can be constructed for different PVC core
    densities and carbon fibers arrangement

    • For a given stiffness, the required core thickness decreases as
    the tow width increases.

    • The same solution methodology can be used for other loading
    configurations.

> The fire tests results discussed in chapter 6, lead to the following
> conclusions:

1.  • For the OSU test, the peak heat release rate can be lowered from
    68 and 85 KW/m^2^ to an average of 21 and 29 KW/m^2^ for 50 Kg/m^3^
    and 250 Kg/m^3^ cores, respectively. The improvement can be attained
    by applying 1 mm inorganic polymer coating.

    • The time to reach the peak heat release rate can be increased from
    50 and 193 sec to 260 and 296 sec for 50 Kg/m^3^ and 250 Kg/m^3^
    cores, respectively.

    • The heat release after 2 minutes decreased from 84 and 127
    KW.min/m^2^ to an average of 5 and -4.7 KW.min/m^2^ for 50 Kg/m^3^
    and 250 Kg/m^3^ cores, respectively.

    • The behavior of the HRR changed from abrupt increase to a rather
    gradual increase till it reached the peak by the end of the test.

    • All the samples with inorganic coating passed the Federal Aviation
    Administration (FAA) criteria and none of the organic ones did.

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1.  • For the NBS test, the level of smoke decreased to 1.5% and 2.8% of
    the level originally exhibited for the control samples for the 50
    Kg/m^3^ and the 250 Kg/m^3^ cores, respectively

    • The inorganic polymer coated samples almost did not emit any smoke
    for the 180 sec.

    • The behavior of the smoke emission changed to much desired
    behavior for the post-crash scenarios.

    • All the samples with inorganic polymer coating passed the NBS
    passing criteria with a level of emission that did not exceed 5% of
    the Federal Aviation Administration (FAA) upper limit.

Based on the results presented in chapter 7, the following conclusions
can be drawn. Note that the maximum bending moment region was heated
using a heating element.

1.  • After 5 minutes of exposure to temperature up to 700^o^C, all the
    samples sustained more than 90% of its strength. This time limit is
    important for passengers to escape from an airplane in a post-crash
    scenario.

    • The performance of cores made with PVC 50 Kg/m^3^ was better. The
    reason is this core absorbed more Geopolymer resin, which improved
    the mechanical behavior by providing some confinement for the cell
    walls preventing them from buckling and deforming, which prevented
    the wrinkling from occurring. It improved the fire characteristics
    as well, by providing extra layer of fire proof material. This can
    be easily verified by comparing the weight gained from the
    reinforcement for both core types. The weight gain was 330% for the
    lightest core and the corresponding number for the heaviest core was
    45%.

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1.  • After 30 minutes, the 50 Kg/m^3^ core reinforced with one and two
    tapes sustained its full strength after being exposed to 350^o^C.
    The 50 Kg/m^3^ core reinforced with one tape and two tapes sustained
    30% and 95% of their strength after exposure to 350^o^C.

    • For exposure temperature of 700^o^C, the 50 Kg/m^3^ core
    reinforced with one sustained 40% of its strength and two tapes
    reinforcement provide the full strength after 30 minutes of
    exposure. On the other hand, the 250 Kg/m^3^ core sustained about
    20% of its strength after 30 minutes.

    • Because of its high flammability, this test could not be performed
    on organic composites.

Evaluation of sandwich beams with inorganic syntactic foam and inorganic
polymer skin presented in chapter 8 lead to the following conclusions.

1.  • It can be feasible to produce inorganic syntactic foams by mixing
    cenospheres and Geopolymer matrix. The primary problem is shrinkage
    during curing. This aspect needs further investigation.

    • Flexural properties of the core (strength and stiffness) improved
    after the exposure to 1050^o^C. The author believes that further
    curing or polymerization occurs when the samples are heated to
    1050^o^C.

    • The reinforced samples lost strength when exposed to higher
    temperature. This is consistent with the behavior of Nextel™ 610
    fiber used for reinforcement, that loose 65% of strength at
    1050^o^C.

    • The workability of the slurry decreased with the increase of the
    filler content.

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1.  • The mixes exhibited some shrinkage cracks during curing; it could
    be detected the most in the 50% mix. The author believes that these
    cracks could be controlled by introducing chopped fibers into the
    mix.

**DeFazio**

**CONCLUSIONS**

The results presented in the thesis focus on the use of an inorganic
matrix composite to reduce the curing temperature and processing costs
generally associated with typical high temperature composites. The
following will highlight significant conclusions based on the results
from experimental testing.

• The optimum curing temperature is 400ºC for the inorganic matrix
composites. This is a significant advantage compared to the 1200ºC
minimum curing temperature for typical high temperature composites.

• The low curing temperature makes it possible to produce high volume
composites without the need for large processing equipment.

• The inorganic composites cure at low temperatures, but can perform at
extreme temperatures beyond 1000ºC.

• Typically, composites with higher densities experience higher flexural
strengths.

• Increasing the exposure temperature decreases the density and flexural
strength of IMCs

• An increase of alumina powder in the matrix results in a more
thermally stable composite, as well as increased flexural strengths.

• A combination of hot-pressing and vacuum bagging fabrication
techniques produces high quality composites with minimal impurities.

These composites have the least amount of air voids, highest densities
and flexural strengths, as well as high product consistency.

• The stress-strain response of the coupons is linear elastic. In all of
the tests the failure was brittle with no post peak resistance.

• Alumina ply laminates have the lowest flexural strength of 20 MPa at
the cured temperature. At 1050°C the strength reduces to 11 MPa.

• High modulus carbon fiber IMCs have a flexural strength of 52 MPa and
elastic modulus of 39 GPa. At 1050°C the flexural strength reduces by
10% while the modulus of elasticity increases by 25%.

• Bulk alumina IMCs have a flexural strength of 65 and 50 MPa at 400 and
1050ºC, respectively. The elastic modulus ranges between 50 and 60GPa at
these temperatures.

• The flexural strength of inorganic matrices reinforced with high
quality short ceramic fibers is 129 and 72 MPa at 400 and 1050°C,
respectively.

The modulus of elasticity at these temperatures is 85 and 53 GPa.

**Feltz**

**Conclusions**

The main focus of this dissertation involves the use of cellulose
byproducts as binding agents for creating composite materials with a
Geopolymer matrix. The literature review that is presented in Chapter 2
provides information about sawdust and rice husk, the two byproducts
used to present this research. Background information about Geopolymer
is also presented in this chapter, as is information regarding the types
and forms of fiber reinforcement that have been tested.

The contents of Chapter 3 focused on the mechanical properties of
Geopolymer-sawdust particleboard. Discussed in this chapter were
observations of these composites when subjected to loading in both a
compressive and flexural state. Analysis of these findings leads to the
following conclusions:

-   Geopolymer-sawdust particleboard is easy to produce and mold, and
    the shape and dimensions of the molds may be customized to fit any
    specified needs.

-   Increasing the volumetric ratio of sawdust to the particleboard
    mixture will result in a lower compressive strength and a lower
    modulus of elasticity.

-   Both glass and carbon are useful in obtaining increased strength and
    stiffness values in manufactured sandwich beams.

-   The type of reinforcement applied to the core particleboard beam
    strongly influences the beam's moment capacity. In general, carbon
    will provide better reinforcement than either AR-Glass or E-Glass.

-   Adding additional reinforcement to a sandwich beam will increase
    both its strength and its stiffness.

-   Carbon fibers significantly increase the strength and stiffness of a
    sandwich beam without significantly increasing its weight. This is a
    very useful trait in fields such as aerospace technology.

    Chapter 4 investigated the use of rice husk as another binding agent
    for Geopolymer, and analyzed its mechanical properties in
    compression and in flexure. The following conclusions were drawn
    regarding the use of Geopolymer with rice husk:

-   Geopolymer-rice husk particleboard is easy to mix. However, rice
    husk does not appear to readily absorb Geopolymer, and the resulting
    mix is difficult to handle. Consequently, there was some trouble in
    molding the product, though the material may still fit a mold of any
    specified shape and dimension.

-   Increasing the volumetric ratio of rice husk in the particleboard
    mixture will result in a lower compressive strength and a lower
    modulus of elasticity.

-   Both glass and carbon are useful in obtaining increased strength and
    stiffness values in manufactured sandwich beams.

-   The type of reinforcement applied to the core particleboard beam
    strongly influences the beam's moment capacity. In general, carbon
    will provide better reinforcement than E-Glass.

-   Adding additional reinforcement to a sandwich beam will increase
    both its strength and its stiffness.

-   Carbon fibers significantly increase the strength and stiffness of a
    sandwich beam without significantly increasing its weight.

Chapter 5 of this dissertation looks into the impact of Geopolymer on
the fire-resistant properties of Geopolymer-sawdust particleboard. Based
on the findings presented, the following conclusions may be made:

-   Geopolymer-sawdust particleboard serves as an excellent material for
    fire protection purposes when subjected to FAA standards.

-   Decreasing the ratio of added sawdust to Geopolymer-sawdust
    particleboard improves the fire-protection traits of the composite
    because less Geopolymer is absorbed by each particle. Less heat and
    smoke are given off as the sawdust ratio decreases.

-   The addition of carbon reinforcement is effective in reducing the
    short-term heat release and the smoke emission of Geopolymer-sawdust
    particleboard when an ignition source is applied. The effectiveness
    of this reduction is dependent upon the type of reinforced that is
    applied.

**Future Research**

Based upon the observations made and conclusions drawn from the research
presented in this dissertation, the following future research
opportunities are desired to further increase and improve knowledge
regarding the use of industrial byproducts to create Geopolymer-based
particleboard construction materials:

-   Further research needs to be performed to determine the impact of
    the physical traits of sawdust on the behavior of Geopolymer-sawdust
    particleboard. These traits include the species of tree from which
    the sawdust is obtained and the size of the sawdust particles.

-   Further research needs to be performed to determine the impact of
    particle size on the behavior of Geopolymer-based particleboard made
    from rice husk. Fine-milled husk was used for this dissertation
    because its consistency is similar to that of saw dust. It is
    desired to obtain rice husk particles that are larger than those
    used, and to analyze the impact that husk size plays in the
    mechanical behavior of this composite particleboard.

-   Future research should be performed to analyze the fire protection
    traits of particleboard created from mixing Geopolymer and rice
    husk. As previously stated, qualitative analysis of Geopolymer-husk
    particleboard revealed that Geopolymer may not have been easily and
    readily absorbed by rice husk. Based on this, it is necessary to
    examine how Geopolymer-husk particleboard will behave when subjected
    to fire protection testing.