Metal Foams Matrices in Aluminium Composites Research Project

This project delves into the realm of metal matrix composites, specifically focusing on aluminium metal matrix composites (AMMCs) and their enhancement through metal foams. The research investigates the properties of metal foams, including their structural and mechanical characteristics, and explores various production processes such as direct gas injection and foaming precursors. The project aims to understand how different reinforcements and foam types influence the properties of aluminium composites, making them suitable for specific applications. The literature review covers the properties of metal foams, production methods, and applications, including structural and functional uses. The methodology outlines the research approach, while the data analysis classifies metals based on their properties and applications of composite metals. The project concludes with recommendations for the most effective production procedures and considerations for applying these materials in different contexts. The project also addresses the research gap, seeking to understand the impact of foam properties on applications. The project also examines the properties of metal foams, production methods, and applications to provide a comprehensive understanding of the material's potential.

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Abstract
A metal matrix composite refers to a composite that has two or more reinforced materials that
have been added to it so as to enhance the properties of the composite. A metal matrix receives
more favour than polymer matrices owing to their ability to satisfy the engineering demands.
Aluminium metal matrix composites include such composites as which aluminium has been used
as the matrix and include numerous reinforced materials that are embedded into the matrix.
Owing to their qualitative properties such as high thermal conductivity, low density, excellent
mechanical properties, high damping capacity, high specific strength, high resistance to
temperature, low thermal expansion coefficient, high ratio of strength to weight, corrosion
resistance and high resistance to wear as well as high abrasion, they have remained to be on high
demand. The various properties and applications of aluminium metal matrix composite foams
and the production processes including direct injection of gas injection of gas and foaming
precursors are studied. Recommendations are made that the two production procedures to be the
most ideal in the production of composite metals and consideration to be given to the properties
before they are applied for various use.

Contents
Abstract.......................................................................................................................................................2
CHAPTER ONE: INTRODUCTION...................................................................................................................4
Background of the Study.........................................................................................................................4
Aims and objectives.................................................................................................................................5
Research Gap and Research Questions...................................................................................................5
Innovation and Significance, Expected Outcomes...................................................................................6
Resource requirements...........................................................................................................................7
CHAPTER 2: LITERATURE REVIEW................................................................................................................8
Properties of Metal Foam........................................................................................................................8
Structural properties...............................................................................................................................9
Mechanical Properties of Metal Foams Matrices of Aluminium Composites........................................10
Elastic Response................................................................................................................................10
Mechanical properties...........................................................................................................................13
Production Process................................................................................................................................18
Production of Aluminium Composite Foams through direct forming by gas injection......................20
Foaming of precursors.......................................................................................................................21
Applications of aluminium Alloy Composites........................................................................................22
Structural Applications......................................................................................................................22
Functional Applications.....................................................................................................................25
CHAPTER THREE: RESEARCH METHODOLOGY...........................................................................................28
Preliminary Development of the project...............................................................................................29
Timeline.................................................................................................................................................29
CHAPTER FOUR: DATA ANALYSIS...............................................................................................................30
Classification of metals based on their properties.................................................................................30
Applications of composite metals based on their properties................................................................32
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS.........................................................................35
References.................................................................................................................................................37

CHAPTER ONE: INTRODUCTION
Background of the Study
A metal matrix composite refers to a composite that has two or more reinforced materials that
have been added to it so as to enhance the properties of the composite. A hybrid metal matrix
composite on the other hand has three or more composites that have been brought together with
the matrix. Other than the common metal matrix composite, there exits polymer matrix
composite, PMC, as well as ceramic matrix composite, CMC. Generally, a metal matrix receives
more favour than polymer matrices owing to their ability to satisfy the engineering demands.
Composites have become the top most promising materials in the recent past with modern
science applying the concept of mixing two or more various materials to come up with better
quality materials Rohatgi et al., 2006. Such combinations results into unique properties which are
in most cases advantageous. There is starting recognition and acknowledge of the commercial
uses of composites by the composite industry and thus increases the chances of greater business
opportunities in both the automotive and aeroscope sectors. Aluminium, titanium and
magnesium alongside their alloys are the frequently used metal matrix.
Aluminium metal matrix composites include such composites as which aluminium has been used
as the matrix and include numerous reinforced materials that are embedded into the matrix.
Among the most commonly used reinforced materials for aluminium metal matrix composites
include red mug, silicon carbide, ly ash, cow dung, graphite and rice husk among other
reinforced materials.
Owing to their qualitative properties such as high thermal conductivity, low density, excellent
mechanical properties, high damping capacity, high specific strength, high resistance to
temperature, low thermal expansion coefficient, high ratio of strength to weight, corrosion

resistance and high resistance to wear as well as high abrasion, they have remained to be on high
demand. This matrix offers lesser wear resistance in comparison to steel and thus widely applied
as a matrix metal. Numerous and wide range of techniques can be used in the manufacture of
aluminium metal matrix composites including squeeze casting, stir casting, powder metallurgy,
and chemical vapour decomposition among other production methods. Of the manufacturing
techniques, stir casting has remained to be the most common method that is adopted by analysts
and researchers.
Aims and objectives
Aim of this research is to explore production process, properties, and applications of metal foams
matrices of Aluminium Composite so that researcher can understand what reinforcements or
metal foams can be used to make aluminium composite suitable for specific applications. To
achieve this aim of the research project, following objectives would be fulfilled:
 To understand properties of metal foams matrices of Aluminium Composites
 To understand various methods of AMC metal foams production
 To explore various applications of Foamed AMCs
 To understand what types of metal foams add properties to make the metal suitable for
specific applications
Research Gap and Research Questions
Aluminium metal matrix composites among other metal composites have been in the market for
decades and their applications have cut across all the sectors both in the industry and domestic
sectors. Following their qualitative properties such as high thermal conductivity, low density,
excellent mechanical properties, high damping capacity, high specific strength, high resistance to
temperature, low thermal expansion coefficient, high ratio of strength to weight, corrosion

resistance and high resistance to wear as well as high abrasion, they have remained to be on high
demand. This matrix offers lesser wear resistance in comparison to steel and thus widely applied
as a matrix metal. Numerous and wide range of techniques can be used in the manufacture of
aluminium metal matrix composites including squeeze casting, stir casting, powder metallurgy,
and chemical vapour decomposition among other production methods. Despite the numerous and
varieties of applications of matrix composite foams, not so much has been explored when it
comes to various properties of these foams and how these properties influence their applications.
An understanding of this scenario would be exploring the various composite metals and using the
various properties as the basis of classification. This would begin at the point of classification of
the various known metals using their identifiable properties.
Among the research questions include:
 What are the properties on which metals are classified?
 What are the properties of various composite metals?
 What are the various applications of composite metals?
 Which production methods are recommended for composite materials?
Innovation and Significance, Expected Outcomes
A comprehensive study into the various metals, their properties and the composite metals would
offer insights into how best appropriately the composite metals can be applied based on the
studied properties. It is thus expected that by the end of this study, there will be a clear cut and
elaborate guidelines that can be followed in the utilization of composite materials for various
purposes. In so doing, better quality equipment and products will be attained as focus will be
directed on the best mix as dictated by the prevailing circumstances.

Resource requirements
For this work, the researcher would not need any financial or human resources other than the
researcher. For the research, the researcher would need to explore the journal articles and
research reports from the library. For this, the researcher would use the college library and the
online sources like Google Scholar and other online research databases to collect required data.
As the data can be collected by a single individual if sufficient time is provided, the research
would not need any other human resource for the current research except the research who would
be visiting the library and online sources to get access to the reports and related data.

CHAPTER 2: LITERATURE REVIEW
For numerous years now, there have been tremendous attempts among scientists and engineers in
coming up with porous metals and metal foams in a bid to copy the naturally porous materials
including bones, cork and coral. Metal foam is a cellular structure that is composed of a solid
metal having a large volume fraction of pores that are filled with gas. The pores may be sealed or
be in an interconnected network. When the pores are sealed, the foam is referred to as closed-cell
foam while the foams are called open-cell foams when in an interconnected network. The closed-
cell foam is commonly known as the metal forms while the open-cell form is called a porous
material. Aluminium is the most commonly used in the manufacture of metal foeman even
though there are other numeracy metals that are applicable among the tantalum and titanium
Jiejun et al., 2003.
Properties of Metal Foam
The properties of the foam of aluminium metal matrix composites are members of a group of
materials known as cellular solids which are often defined to be having a porosity of up to
greater than 0.7. Plants and animals are the main producers of natural foams include bone and
coke while arrival foams many be produced from various materials among the metals, polymers
and ceramic. The two main categories of manmade foams include closed-cells and open-cells.
Metal form is able to combine the properties of cellular materials with the metals from which
they are a component. This makes metal foams be beneficial when it comes to lightweight
construction following the high strength to weight ration besides the functional and structural
properties such as sound management, heat management and energy absorption. It is possible to
foam numerous metals and their corresponding alloys.

Structural properties
Aluminium alloy foam has numerous structural parameters among them numbers, mean size,
thickness, shape and geometry of the pores, distribution of the pores, defects as well as the
intersections in the thickness and cell walls, cracks and defects that occur to the external dense
surface that os used in describing the cellular architecture of the foam.
There has been progress observed in comprehending the correlation between the morphology and
the properties. In as much as the correlation has not been exactly established, it os often assumed
that there is an improvement in the properties in cases where all the individual cells which make
a foam are of the same size and spherical shape Rohatgi et al., 2006. This is the assumption even
though there have not been experimental verifications of the claim. It os not debatable that the
density of a metal foam and the properties of the matrix alloy have an impact on the modulus and
strength of the foam achieved. In all the studies, it has been indicated that the theoretical
anticipated properties are superior to the actual properties owing to the various structural defects.
This calls for a better control of the pores as well as a reduction in the structural defects. A great
scatter of determined properties is yielded by the variations in the density and imperfections
which poses a threat to the reliability of the formation of the metal foam. Missing or wiggled cell
walls lower the strength which consequently results into a reduction in the absorption of
deformation energy under compression.
Mechanical studies and findings have established that deformation of the weakest region of the
structure of the foam selectively results into the formation of crush-band. The thermal and
acoustic properties of the foam may also be influenced by the morphology and interconnection of
the cells. It is generally acknowledged that foams that re having their pores uniformly distributed
and are free from defects are often accepted and desirable. Such properties make it very easy to

predict the nature of the foam. It is only after the prediction of the properties of the foam that it
will be possible to take into consideration metals as a reliable foam material for engineering
purposes and will have the capability of competing the other available classical materials. Even
with the tremendous improvements that have been made to metals foams in the last decade, the
resultant metal foams are still held within the hook of non-uniformities (Ramnath et al., 2014).
There are aims and attempts to generate structures that are more regular and have minimal
defects in a way that is more reproducible which has remained the main challenge of research in
the field of production of metal foams.
Among the main properties of metal foam include
 Extremely high porosity
 High strength
 A material that is ultra-light in which between 75-95% of the volume is composed of
void spaces
 Very high compression strength and excellent energy absorption characteristics
 Low thermal conductivity
Mechanical Properties of Metal Foams Matrices of Aluminium Composites
Elastic Response
The use of appropriate and reliable values for the elastic properties forms a fundamental aspect
in the design of components of metal foam. The frequently of non-destructive resonance has
been used in the examination of the elastic properties of metal foams. This is due to the fact that
the use of mechanical tensile testing that has conventionally been used in the determination of
the elastic properties is expensive, time consuming as well as subject to interpretation for the
case of non-linear moduli (Bodunrin et al., 2015).

Plastic response parameters as compression strength, flexural strength or energy absorption
capacity are among those that are used in the determination of plastic response of metal foams.
In terms of compression strength, metal foams have been found to undergo plastic deformation
in a typical yielding. They possess a deformation behaviour that is universals in which the initial
elastic deformation is closely followed by plastic yielding. In most cases, the change between the
two regimes can be characterized by piper and lower points of yield Rohatgi et al., 2006. There
are four ways of defining the yield strength of metal foams including:
 Stress at a specific strain
 Upper yield point
 Extrapolated stress and
 Lower yield point
Alloy foams that have been manufactured through the PM method have their cellular
structures made up of pores that have varied shapes and sizes. They have large distribution of
the cellular pores having shapes that are irregular. The closed pores are mostly having a
spherical or polyhedral geometry. The bottom and lateral sides of such metal foams have
spherical pores that have thick cell wall thickness while the polyhedral pores which have thin
thickness of the cell walls are majorly distributed in the top of the various samples of the
foam.
A higher density gradient is achieved in foam due to the distribution of the solid metal in the
foam which is basically non-uniform. These materials are composed of broader diameters of
the cell distribution curve. A large number of small pores dominate the distribution of the cell
size with mist of the cells having their diameter to be less than 2 mm. There are also

significant observable morphological defects among the spherical micropores and cracks in
the cell walls as well as wiggles and dense skin (Banhart, 2000). The distribution of the cells
is such that each of the cells has about 5 other cells in its vicinity with the distribution of the
thickness of the cell wall having an asymmetrical shape.
The smallest thickness of the cell wall is approximately 70 um with the maximum cell wall
thickness being about 500 um. The cell wall thickness of a cell is a factor of the density of
the foam. As can be observed in the figure(s) below, the external dense surface skin thickness
is varied in the samples in which the lateral and bottoms sides have the higher values Rohatgi
et al., 2006. The microstructure of the massive cell material is yet another structural feature
which impacts on the mechanical behaviour of cell material. Depending on the composition
of the alloy and the process of manufacturing, there can be observed in the final structure
metallic dendrites, precipitates, eutectic cells or even particles. Particles of the same density
but varied aluminium alloys may attain different plateau stress.
Figure 1: Pore geometrics (spherical), (b) polyhedral and (c) geometries