Properties, Production Process, and Applications of Aluminium Metal Matrix Composite Foams

This research explores the properties, production process, and applications of aluminium metal matrix composite foams. It discusses the various reinforced materials, production methods, and applications of foamed AMCs. The study aims to provide guidelines for the utilization of composite materials for various purposes.

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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

Figure 2: Thickness of the dense surface skin in various sections in a sample (top), (b) lateral
and (c) bottom sides
Figure 3: Cellular structure of AlSi7 (a) and AlSiMg (b) foams. (c) is the distribution of cell
pores as a function of the number of cell pores
Mechanical properties
Numerous literature studies have been conducted with regard to the mechanical properties of
metal foams. Gibson and Ashy, 2000 provide an elaborate and broad survey that offers a
comprehensive understanding of the mechanical properties of various cellular solids. In other
cases, scholars and researcher have conducted experiments that are aimed at examining the
behaviour of metallic foams under varied loading conditions, specifically the properties of metals
foams when subjected to impact loading.
Owing to the possibility of regulating the load displacement behaviour using appropriate choice
on the material for the matrix, relative density as well as the cellular geometry makes foams an

excellent material for structures that absorb energy. From the numerous methods used in
mechanical testing that are available presently, uniaxial compressive mechanical tests tend to be
the most commonly used adopted in the determination of the compressive behaviour as well as
the energy that is absorbed by the various foams. The key parameters for mechanical properties
include the elastic modulus, plateau strength and yield strength as obtained from the various
curves (Degischerab, 1997).
The curves on stress-strain of aluminium alloy foams illustrate either brittle fracture or plastic
which is influenced by the fabrication of the foam as well as the microstructure. Numerous
parameters affects the compression behaviour of aluminium alloys foams among them the
defects of the cell walls or cellular structure, morphology of the cell which includes the range of
the cell size, the composition of the aluminium alloy gradient samples density as well as the
features of the external surface skin (Elliott & Timulak, 2005). The impacts of the density
alongside the design of these foams on the mechanical features and properties are sophisticated
and strong.
Various mechanisms are observable among them ductility and brittleness depending on the
material that is used in making the foam. The compressive properties of the foam among them
modulus, energy absorption and the mean plateau stress heavily rely on the density of the foam
such that their values increase with an increase in the density of the foam.

Figure 4: Compressive stress-strain curves for various specimens
As is observable from the figure above, there are three characteristic regions into which the
strain-stress curves have been divided. The first region labelled (I) refers to the inelastic region in
which there is an increase in the load with a corresponding increasing in the compression
displacement and the increases are almost linearly (Drenchev et al., 2005). This occurs in the
elastic deflection of the pores walls. The second region, which closely follows the first region, is
labelled Region II which is a plastic collapse plateau which has an almost steady compression
load in which the pore walls generate or fracture even as increasing deformation does not call for
an increase in the load. The last region which is the third region is the densification of the foam
in which a rapid increase in the load occurs upon the crushing together of the cell walls.
After undergoing an elastic loading, the foams exhibit plateau regions that are more or less clear.
The plateau stress is significant in the characterization of the behaviour of absorbing energy and
provides an excellent material property in terms of the compression performance of metallic
foam. There exist the measurements of the plateau stress relative to the various methods which
are used in taking such measurements on the course of the curve of stress-strain (Duarte &

Ferreira, 2016). There are various modes and mechanisms of failure that have been identified
with the various regions of these foams with regard to load displacement.
The bending of the edges results into elastic formation. Elastic formation also results from
trapping of air molecules inside the cells as well as elongation of the cell walls. This deformation
is rarely visible. Elastic deformation due to air molecules being trapped inside the cell wall is
almost complete reversible and takes place through the entire sample. The cells begin to collapse
as soon as the elastic limit is reached, which in most cases occur by distortion, sliding and/ or
rotation of the cell walls and edges with permanent deformation (Given, 2008).
At the plateau stage of the load-displacement curve, a progressive collapse is realized. Owing to
the structure of the foam which is irregular, this kind of deformation tends to be non-uniform.
Such factors that are responsible for the non-uniform thickness include distribution of the pore
sizes and the thickness of the cell walls. There may be a correlation between the slope which
characterizes the region and the compression fluid that has been captured inside the cells or even
as a result of tensile strength that is observable in the cell walls. An increase in the density results
into a corresponding increase in the slope and the collapsed cell shape is found to be quite
different from the initial shape due to the components of bended and distorted cells that are
found in its structure that could even be touching each other.
However, generally the cells walls for not fracture with the initial collapse starting in a small
group of cells that are found in the region that is of the lowest local density. Collapse does not
take place in all the available cells, especially in those cells that have higher loads or are less
resistant. The collapsing of a cell triggers the collapse of the neighbouring cells (Bodunrin et al.,

2015). Further, the collapse of the neighbouring cells may lead to the formation of successive
layers which would finally lead to the formation of a single band of deformation.
Aluminium alloy foams are in most case used as a filter material among lightweight structures in
impacting or crushing high velocity or even as acoustic or thermal insulation devices. The
capability to absorb energy by these foams may as well be determined using the behaviour of
stress-strain compression of the material which is calculated form the area under the stress-strain
curve. Since foam materials have a constant stress plateau, they have the capability of absorbing
higher energy levels as compared to dense aluminium alloys Rohatgi et al., 2006. Most of the
energy absorbed is irreversibly changed into plastic deformation energy which offers a further
benefit of the foamed aluminium.
Under the same levels of stress, deformation of the dense material occurs in the reversible linear-
elastic stresses regime thereby leading to the generation of most of the energy that was stored
upon removal of the load. Aluminium alloy foams have higher capabilities of energy absorption
in which an increase in energy absorption leads to a corresponding increase in the density hence
exhibiting direct proportionality.
Figure 5: Load displacement curves of a AlSi7 when subjected to compressive loading

Figure 6: (a) absorbed energy per volume in a specific strain interval in the area under the stress-
strain curve. (b) Absorbed energy curves of AlSi7 foam under compressive loading at various
densities
Production Process
Metallic melts can be foamed through the creation of bubbles of air in the liquid. The gas babbles
inside the metallic melt move to the surface following the high buoyancy forces that are present
in the liquid that is of high density. This can be challenge and hence can be prevented by
increasing the viscosity of the molten metal. This is achievable through the addition of fine
ceramic powder or any other alloying elements so as to come up with stabilizing particles that
are used in the melt. There are three main ways that can be deployed in the formation of metallic
melts:
Injection of a gas into the liquid metal extracted from an external source: This is the method
that is used in the foaming of aluminium and the associated aluminium alloys. Aluminium
oxides, magnesium oxide and silicon carbide are among the particles that are used in achieving a
higher viscosity of the melt to be formed (Banhart, 2000). It this method, it should be ensured
that the mixing technique remains consistent so as to ensure that the particles are uniformly
distributed throughout the entire melt. The melt is then foamed through injecting gases such as

nitrogen, air as well as argon into it through the use of rotating impeller or even vibrating
nozzles.
Precipitating the gas which has just been dissolved in the liquid-This is also called solid-gas
eutectic solidification or otherwise gasar which basically means gas-reinforced. Research has
established that some liquid metals are able to form eutectic systems with hydrogen gas Rohatgi
et al., 2006. Upon melting one of such metals in an atmosphere of hydrogen under very high
pressures of about 50 atm, a homogenous melt that is charged with hydrogen is achieved. The
melt is likely to have a eutectic transition in which it forms a heterogeneous solid gas system
upon lowering of the temperature. It is required that the solid gas system have a eutectic
concentration which would then permit a segregation reaction at a certain temperature.
Solidification of the melt begins resulting into the precipitation of pores and their trapping in the
metal. Elongated pores that are aligned in the direction of solidification are mostly formed.
Formation of an in-situ gas in the liquid through admixing the agents of the admixing has
releasing to the merit used: This is a direct method of production of metal foams and involves
the addition of a blowing agent to the melt as opposed to injecting a gas into the melt. The gas is
added into the melt through the use of such compounds as carbonates and hydrides (Elliott &
Timulak, 2005). These compounds decompose and release bubbles of gas upon heating in a
semi-solid pellet or a liquid metal. In order to achieve uniform sizes of the pores and density for
the porous metals, it os required that the resultant foam must be stable. Shinko Wire Company
located in Amagasaki, Japan is one of such companies that have for a long time been using those
techniques in the production of foams Rohatgi et al., 2006. Approximately 1.5 wt. % of calcium
metal is added to the aluminium melt at a temperature of 680⁰C after which proper mixing of the
melt is done and an increase in the viscosity begins as a result of the formation of calcium oxide,

calcium aluminium oxide or even intermetallic of Al4Ca. This assists in the thickening of the
liquid metal.
Upon the attainment of the desired viscosity, a blowing agent is added which in this case is
titanium hydride that serves to introduce hydrogen gas into the hot viscous liquid. This results
into a gradual and slow expansion of the melt which then fills the foaming vessel. Foaming must
be done a constant pressure. The liquid foam changes to solid aluminium foam upon cooling of
the vessel to a temperature that is below the melting point of the alloy and this can be removed
from the mold to be taken through further processing.
Production of Aluminium Composite Foams through direct forming by gas injection
Gas injection is one of the most commercially exploited methods of foaming aluminium alloys.
Aluminium oxide, silicon carbide among other ceramic particles is used as admixture so as to
make the alloy foam able. The sizes of the particles that are used in the reinforcing ranging from
5 to 20 um with a volume fraction that ranges from 10 to 20%. There are specially designed
injectors that are described to be rotating or vibrating in the injection of the gas which is in most
case air. The resultant foam that has been formed moves to the top of the liquid from which it is
taken from using a conveyor belt before it is allowed to cool and solidify. The resultant foamed
material is used either by cutting it into the required shape upon foaming or in the state that it is
taken off using the conveyer belt from the casting machine. This method of foam generates large
volumes of foams that have low densities (Bodunrin et al., 2015). Stabilized Aluminium Foam
that is manufactured in Cymat, Canada follows the same procedure in its production process.

Foaming of precursors
This is yet another technique that can be used in the foaming of metals and involves preparation
of a precursor that is made up of uniformly dispersed blowing agent as opposed to the formation
of the foam directly. In this method of foaming, the foam is produced through melting the cursor
during which there is evolution of the blowing gas and bubbles are generated Rohatgi et al.,
2006. There are numerous procedures that are used in the production of foam able precursor one
of such being the inclusion of a hot uniaxial pressing that is used in compacting the powder
mixture at temperatures that are close to the thermal decomposition of the used blowing agent.
This procedure offers the yielding of not less than 99% of relative density of the precursor.
Figure 7: Precursor materials of aluminium alloy

The density as well as the distribution of the particles of blowing agent into the metal matrix is
the main parameters that are used in foaming of precursors all of which can be evaluated through
the use of a scanning electron microscope.
Figure 8: Foam able precursor sample of the aluminium alloys
Applications of aluminium Alloy Composites
Structural Applications
The high stiffness of lightweight materials makes them a preferred in different applications.
Standard products in the market among them honeycomb panels utilize the cellular structure as
the core alongside brazed or glued face sheets in the provision of the desirable properties.
Despite being cheap, these lightweight materials are accompanied by other disadvantages among
them inability to be curved, resistance to high temperatures as a result of the glue and they
cannot be recycled. Aluminium alloy foams have been used in the manufacture of aluminium
foam sandwiches, AFS as well as steel aluminium sandwiches, SAS which have proved effective
and efficient in structural applications (Srivastava & Sahoo, 2007).
Aluminium foam sandwiches panels are used as support frames for example for mirrors and solar
panels and in any other places in which there is need for light and rigid metallic panels. In most

cases, the customers prefer giving the material to be used as panels and then go ahead to
manufacture their own products by themselves. More often than not, they opt to keep their
innovative field of application a top secret to enhance a competitive advantage on the products
that are offered in the market.
An excellent example in this case is the industrial machines in which beams and columns that are
filled with foams are found to be light and stiff. As a result of the reduced inertia, these columns
and beams are able to move swiftly and can accurately be positioned. Examples include drilling,
printing, textile, milling, blanking or pressing industrial machines. Still, damping of the system
and of for example an additional tool for vibration can be used in enhancing the performance of
the accuracy of positioning and wear, minimize problems of fatigue and enhance the operational
lifetime (Degischerab, 1997). The figure below is an example of a high-speed milling machine
application of Niles-Simmons in conjunction with the Fraunhofer-Institut fur. As can be seen in
the diagram, the sliding bed has been made of 11 welded AFS parts in which the construction is
28% light relative to cast part that has the same stiffness even though with having improving
vibration damping.
Figure 9: Example of a high-speed milling machine application of Niles-Simmons in conjunction
with the Fraunhofer-Institut fur

The new developments of lightweight materials tend to bring about some benefits to the
automotive industry. For the scale of large serial production, consideration is not only confined
to the properties and the cost of the material but also other engineering and strategies aspects
among them the need to redesign other components, the quantity of the available suppliers as
well as the capability of the system to integrate. Apart from the large number of prototypes
available, numerous large series opted into production (Elliott & Timulak, 2005). An example of
such is the door sill that was filled using aluminium foam so as to reinforce the frame besides
increasing its stiffness alongside its behaviour should there be a side crash in the high premium
cars where they are used. The example is as shown in the diagram below.
Figure 11: Door sill filled using aluminium foam so as to reinforce the frame
The emergence of new opportunities for applications of AFS in the automotive industry provides
new developments in the segments of the electric cars as lightweight construction becomes a
compulsory requirement. Moreover, the design of cars is important owing to the rearrangements
of the components which make it a possibility to take into consideration the cellular solutions
right from the beginning of the design phase. Another important factor yet is safety in which a
minimized volume, hence light and effective protection system for a crash is needed.

In the exploration of the capability of energy absorption, of metallic foams, Foamtech offered
crash elements that a required for a guardrail. A literature analysis of the suitability of the
aluminium foam as an element of protection ib aluminium pillars was done where it was
established that an aluminium pillar for a Ford passenger car that is filled with a reinforcement of
aluminium foam recorded an improvements of about 30% in the absorption of crash energy when
it was just at 3% of an increase in its weight. An improvement in these values can be achieved
through a redesign of the components as opposed to a simple filling.
With regards to mobility, consideration must also be given to the railway industry in which they
has been evolution of promising prototypes in the recent past that may be used as possible future
serial application. AFS foam panels were used as a component of the floor of a wagon of the
metro in Peking in which it served in a continuous operation without any challenges for several
years. The most recent prototype is the cover of the power head of the Intercity Express Train
which is made from welded AFS plates as well as carbon fibres mainly in the front side and has
an accumulated length of about 6 m (Duarte & Ferreira, 2016). The same stiffness achieved a
weight reduction of 18% with improvements in the vibration damping and a reduction in steps of
manufacturing in comparison to the traditional and conventional procedure of construction.
These examples among other are illustrative of the AFS panels or the metallic foams against
honey comb panels that has seen the application of the AFS panels grow tremendously over time.
Functional Applications
There is a wide palette of the functional applications of metallic foams that are available in the
market. Perforated sheets of metal have been used in planking the ceilings in large rooms and
auditoriums for the purposes of sound control. At the open surface of the foam, guidance and
redirection of the sound waves into the interior of the foams occurs in which they are trapped and

damped after undergoing numerous reflections. The distribution of the pore size and the various
orientation permit effective damping across the broad frequency spectrum. Such an application
also is perceived to be architectural but it is classified as a functional application since their main
role is absorption of sound. This application brings together the advantage of the capability of
self-supporting, lightweight of the large metallic foam panels that are manufactured of open cell
with the design component. Shown in the figure below are the ceilings of an audience as well as
s restaurant that have been covered using allusion foam.
Figure 12: Ceiling of (a) audience hall; and (b) restaurant that has been covered using Alusion
foam for the second control
More applications of sound absorption using Alporas foams are found in trains, elevation, metro-
tunnels as well as on the sides of an elevated highway. Developments are also on gong that are
aimed at coming up with products that are applied to concert halls, conference rooms,
auditoriums and non-flammable acoustic absorbers. There are slopes applications in the ship
industry where for example there is prevention of the noise that is generated from the engine
room, the air cleaning system as well as the combustive exhaust pipe using walls that are foamed
from the inside between the cabins. There are also metallic foams used in the metro tunnels for
sound absorption in the railway as well as on the station and tunnel walls in which they are

designed to support the high changes in the air pressures and vibration while at the same time
remaining non-flammable (Degischerab, 1997).
As a result of the resistance of metal foams to high temperatures and chemical substances, in
combination with the properties of sound absorption, open cell foams that are derived from
Alantum have been used as silencers, filters of particles of diesel, mufflers as well as in the
reduction of selective catalysis.
Figure 13: a range of products for functional applications

CHAPTER THREE: RESEARCH METHODOLOGY
This research would use an exploratory study in which the objectives of this research would be
achieved so that conclusions can be made to solve certain problems identified by the researcher.
The aim of this research is to understand how different methods of production and combination
of foaming and composite formation can help modify properties of aluminium to make the
composite suitable for specific applications. Thus, using the exploratory approach, the researcher
would first explore the applications of aluminium composite and identify what properties of
metal are required for these applications. Various production methods would then be explored to
understand how they can produce foamed composite metals with different properties (Elliott &
Timulak, 2005).
For the research, secondary qualitative methods would be used. The secondary sources like
books, journals, and research reports would be used for collecting the qualitative data on
properties, production and application of aluminium composite materials. The data obtained
would be analysed using a descriptive approach that would explain the production processes and
what differential properties are exhibited with these differences in the aluminium composites.
The data obtained would be used to create categories of composites based on their properties and
applications. For this, the researcher would use own knowledge and critical thinking to identify
the properties that are affected by different production methods and the need for those properties
in specific applications. Based on this understanding, the researcher would come up with the
recommendations on the use of appropriate aluminium composites for specific applications
including healthcare, automotive, aerospace, and construction by matching the application needs
with the composite material properties (Given, 2008).

Preliminary Development of the project
The project is in its initial phase where the initial research is done on the properties, production
processes, and applications of foamed aluminium composites. The researcher would further need
to explore each type of composite or production process to understand what properties they add
to the metal and at the same time also explore various applications these composites would be
suitable for. Based on this analysis, recommendations would be made on the use of aluminium
composite metals for specific business or industry applications Degischer, H., 1997.
Timeline
The project would take 40 days to complete involving literature review study secondary data
collection, analysis and reporting with relevant recommendations.
Research Task Milestone Date
Initial Literature review and Proposal – Approved 24th April 2018
Detailed Literature review
Metal Properties 30th April 2018
Production Processes 10th May 2018
Applications 20th May 2018
Data Analysis
Classification of metals based on their properties 25th May 2018
Identifying applications of composite metals based on their properties 30th May 2018
Conclusions and recommendations
Summarizing findings 2nd June 2018
Recommend production methods and composite metals for respective
applications
4th June 2018

CHAPTER FOUR: DATA ANALYSIS
Classification of metals based on their properties
A metal is a material that is in the form of an element, compound or alloy which is often hard
when in the solid state, has a good thermal and electrical conductivity and is shiny or opaque.
Metals are in most cases malleable meaning that they can be pressed permanently until they lose
their shape or can be hammered without being broken or cracking. They are also fusible which
means they can be melted or fused and are also ductile i.e. can be drawn into thin wires.
There are various types and classifications into which metals are put that are based on their
chemical and physical properties. Metals are known to be the hardest known metals on the
surface of the earth. Other than mercury, most of the other metals are often in solid state in
nature. Mercury exhibits a liquid-like motion, can be bent in various shapes and has numerous
applications in human life. Mercy has unique properties and quite distant from the other elements
that are found in the periodic table. It becomes alkaline in nature upon oxidation and reacts with
acids. The metal undergoes rusting upon being exposed to air for quality time. Mercury is
available in the bodies of living organisms in relatively very low quantities.
Metals are classified into five main categories based on the properties:
 Ferrous metals
 Noble metals
 Metal alloy
 Non-ferrous metals
 Heavy metals
Ferrous metals are metals that are composed of a combination of carbon and iron. Due to its
varieties and large scale usage, they are grouped as ferrous metals. Ferrous metals are often hard

in nature and may be made into various shapes. The strength of such metals is such high that
they are usable in the making of heavy machinery as well as equipment. They can tolerate very
harsh environmental conditions as well as heavy machinery. With time, when exposed to
corrosive conditions, this type of metal can corrode and can as well melt under extremely high
temperatures. Examples of this group of metals include steel and iron is normally good
conductors of heat as well as electricity.
Noble metals are just like noble gases in the sense that they rarely react even though they are
able to react under powder or liquid conditions. Generally, this type of metals are non-corrosive
and do not rust upon being exposed to air. Due to their soft nature, they can easily be molded
into various forms, and are a bit costly owing to the aforementioned properties. Examples of
noble metals include platinum, silver and gold.
Noble gases are very malleable and hence can easily be hammered into thin sheets of the metal,
they are often good conductors of electricity and heat and is said to could even be better that
most of the other metal types. A gram of gold is capable of generating one meter square of sheet.
Non-ferrous metals are metals that are used in place of iron in different machinery and other
equipment. These metals are not as heavy as the ferrous metals and are recorded to be less
corrosive as well as softer than the ferrous materials. Owing to the above advantages, non-
ferrous metals remain in very high demand and examples include lead, copper and aluminium.
Just like the ferrous metals, non-ferrous metals are excellent conductors of electricity and heat.
Heavy metals have higher atomic weight as well as high density even though they may be less
strong compared to iron and other metals. These metals are in most cases not widely spread in
nature as is the case with the above metals even though they may be accumulated. Most of them

tend to be hazardous to human health upon internal intake. Examples of heavy metals include
lead, arsenic and cadmium. Most of these metals are generally hard substances which have the
capability of being molded into various shapes; they are excellent conductors of heat even
though mercury is not a good conductor of heat while lead is a poor conductor of electricity.
Heavy metals have numerous applications in the health sector, industries as well as agriculture.
They form part of the few biomolecules that are found both in plants and animals.
Metal alloys are metals that are derived through combination of numerous metals. These metals
are mixed or alloyed in order to attain the required properties among them durability, strength as
well as resistance to corrosion. Still, such metal alloys are applied in avoid or resisting
generation of heat such as in large gun cannons. Such gun cannons tend to heat up during firing
and thus the alloys are made in such a way that they are not heated very fast as is the case with
traditional methods.
Applications of composite metals based on their properties
A composite is a material that is made up of not less than two materials which are combined to
offer properties that are better and superior to the individual constituents. There are numerous
composite materials and various processes that may be applied in the manufacture of composites
that are very efficient and versatile. These processes ideally generate lighter, more durable as
well as stronger solutions in comparison to the conventional and older materials. The main
reason for choice composite materials for use in various components is attributed to its weight
saving in which it is relatively stiff and stronger Kiser, He and Zok 1999. An example could be
the reinforcement of carbon fibre composite that would yield a composite that is five times
stronger than the conventional 1020 grade steel but has just one fifth of the weight.

The industry of composites has turned out to be an exciting and interesting industry as it leads to
the development of new materials, applications as well as processes almost every time among
them the use of hybrid virgin and recycled fibres, quicker and greater automated manufacturing
among other applications, processes and new materials.
Composite metals are applied in almost all the sectors of the economy with its applications
observed in the automotive, marine, medical, rail, aeroscope, construction, defence, oil and gas
among other sectors. In the aeroscope industry, large volumes of fibre reinforced composites find
their applications in the aircraft in significantly small percentages even though the material still
finds sophisticated applications in the very industry. The main considerations for the application
of composite metals in the aircraft industry include high strength, light weight, good distance to
fatigue and high stiffness.
Composites are also used in space applications especially in missiles in which it has led to the
development of primary structures that are used in space vehicles. An example id the satellites in
which the time gap between the manufacture and the concept can be reduced to as low as two
years and the short product runs usually involved the element of the material in the final attained
cost is usually significantly low. Further, in other applications, there are no other materials that
can suitably be used owing to technical challenges. Carbon fibre composites are in most cases
associated with space applications owing to their good thermal stability and high stiffness when
subject to a wide temperature range.
With reference to the construction sector, the main areas in which composite metals have been
used include architectural (domes, structures and curves), civil and infrastructure (pipes, masts
and towers, tanks, modular structures, covers of access, structures for water control), bridges

(enclosures of bridges, bridge decks and structures for full bridges), refurbishment (seismic
retrofiring and strengthening of the existing structures), housing which include architectural
mouldings, sanitary ware and various structures.
Other applications of metal composite matrix include:
 A substrate for high density, high power modules of multi-chip in electronics owing to its
extremely high thermal conductivity as is the case with an alloy of copper and silver
matrix that os composed of 55% by volume of particles of diamond
 An upgrade of a driveshaft of a metal matrix composite is offered by Ford which is made
from aluminium matrix that has been reinforced using boron carbide thereby permitting
rising of the critical speed by the driveshaft through reduction in inertia. This composite
has turned out to be one of the most common modifications that are done for racers which
allow an increase in the top speed much higher than the perceived and outlined safe
operating speeds for a conventional and standard driveshaft of aluminium
 Some automotive disk brakes utilize metal matrix composites for example the ancient
Lotus Elise which made use of rotors of aluminium metal matrix composites in as much
as they exhibit heat properties that are less than the optimal provided ranges.
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS
In summary, 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 with such combinations resulting into unique properties which are in
most cases advantageous. 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. There are two main categories of manmade foams including closed-
cells and open-cells. Metal foam 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.
Various techniques and approaches can be used in the process of manufacturing foams with each
of the techniques having its advantages and shortcomings that need to be addressed to achieve a
success in the application of the chosen technique. Metals are classified into four main categories
based on their properties: heavy metals, ferrous metals, non-ferrous metals and noble metals with
each are having distinguished properties.
From the findings of the study which was mainly based on analysis of the existing literature,
production of aluminium composite foams through direct forming by gas injection and the use of
foaming through precursors are the most recommended methods for the production of aluminium
alloy composites. The resultant foamed material through direct forming by gas injection is used
either by cutting it into the required shape upon foaming or in the state that it is taken off using
the conveyer belt from the casting machine. This method of foam generates large volumes of
foams that have low densities. The use of composite metals in various applications should take
into consideration the properties of the composite metal that is to be used and comparison be
made against the intended application. The application should only proceed as soon as it is
established that the properties of the composite are to the expectations of the expected results.

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