KTU 2019 S8

1. INTRODUCTION- SMART COMPOSITES
Definition:
 As per Author- Kelly, Davidson and Uchino in 2017, Smart composites are defined as the Systemic
composition of smart materials to provide enhanced dynamic sensing, communicating, and
interacting capabilities via Interactive Connected Smart Materials (ICS Materials).
 Smart Composites can be explained simply as these are designed materials ,where smart materials
are embedded in polymer, metal or concrete etc.. to sense, control, communicate etc.
 To get the whole idea of smart composites, We need to understand what is smart material. Let we
discuss in coming slides.

2. SMART MATERIALS
 Smart materials, also called intelligent or responsive materials .
 Author Rogers, 1988- Defined Smart material are the materials which have the ability to change
their physical properties in response to specific stimulus input or environmental changes.
 These stimulus could be pressure, temperature, electric, magnetic filed ,chemical, mechanical
stress, radiation etc.

3. SOME OF THE SMART MATERIALS TYPES
 Piezo Electric Materials.- Materials that produce a voltage when stress is applied.
 Photovoltaic or Opto electronics materials- Converts Light to electrical current.
 Shape memory materials Induce deformation due to temperature, stress change.
 PH Sensitive polymers- Material which changes in volume when PH of surrounding medium changes.
 Halochromic materials-change their color as a result of changing acidity.
 Temperature response polymers-materials which undergo changes upon temperature.
 Thermo electric materials-convert temperature difference to electricity & Vice versa.
 Di Electric elastomers-produce large strains (up to 500%) under the influence of an electric field.

4. FOUR General classification of Smart composites
(1) Structural smart composites;
(2) composites for actuation;
(3) novel functional composites; and
(4) nanocomposites that are enablers of novel functions.

5. (1)STRUCTURAL SMART COMPOSITES
 Structural Smart composites are materials that have the sensing capability to detect stress, strain, fatigue and
damage. monitor the health conditions of structures that are difficult to inspect or repair, such as wind turbine
blades, underground pipes and long-span bridges.
Structural Health Monitoring With Fiber Optic Sensing - YouTube
 Embedding smart material into structural material is an integrated design that is more reliable and compact.
Several types of smart materials or sensors have been adopted in sensitive structural composites. Among them,
fiber optic sensors, piezo electric have been widely studied and adopted.
 Their features include, but are not limited to, immunity to electromagnetic interference, small size, light weight,
durability, low cost for mass production and high bandwidth.
 These features allow large numbers of Smart materials or sensors to operate in the same system and to be
integrated within thin materials.

6. (1)STRUCTURAL SMART COMPOSITES
Continued
Example-1
Optical fiber embedded CFRP composites
 Fiber optic sensors embedded in carbon fiber-reinforced polymer composites can be used to monitor the structural health
in their fabrication, and their in-service condition.
 The below figure shows the fabrication from Mr. Okabe, 2002
 Single mode optical fibers with Fiber bragg grating sensors used.
 optical fibers were coated with UV-cured resin, whose outside diameter was 250 µm.
 the FBG sensor is sensitive to the transverse cracks that run through the thickness and width of the 9
0
◦ply. Moreover,
since the optical fiber is embedded in 0
◦ply to be parallel to the carbon fibers, the matrix rich region around the optical
fiber is so small that it does not deteriorate the strength or stiffness of the CFRP laminates.

7. (2) SMART COMPOSITES FOR ACTUATION
 Materials being used as actuators were referred to as induced strain actuators in the 1980s. The actuation was based on
natural mechanisms that cause actuation strains, including thermal expansion, piezoelectricity, material phase change and
moisture absorption (Crawley and Lazarus, 1991).
 Shape-memory materials were proposed and developed based on the above mechanisms. They are materials like nitinol
etc will deform & deformation can return to their original position to certain stimuli like temperature, stress etc
 Shape-memory composites can be manufactured at a low cost; they are also lightweight and potentially biocompatible and
biodegradable, facilitating applications such as space-deployable components and structures (e.g., antennas and hinges
(Sokolowski et al., 2008), as shown in Fig. )

8. (2) SMART COMPOSITES FOR ACTUATION
Continued
 Shape-memory composites can be controlled using temperature, electricity, magnetic field and light (Liu et al., 2017),
making them flexible in their implementation. After years of development, their recovery stress, production cost and
displacement resolution have all been improved significantly.
 Fiber reinforced polymer composite with Shape memory material is in demand for weight saving application in various
engineering applications.
 Advantages are good mechanical behavior, corrosion resistance.
 FRPs brittle failure issues can be solved when integrating with Shape memory as it can absorb energy leading to better
dampening effect.

9. (3) SMART COMPOSITES WITH NOVEL FUNCTIONALITIES
 Smart composites can also be composites with unusual properties (additional to sensing and actuation).
Example -1
 Self-healing composites are composite materials that can recover automatically after damage (Wang et al., 2015b). The
mechanism of healing can be either intrinsic or extrinsic. Intrinsic healing uses materials’ intrinsic .Extrinsic healing is
based on embedded microstructures (e.g., microcapsules and microvessels) which contain liquid healing agents. In the
event of a crack, the healing agents are released to fill the gap and solidify (Pang and Bond, 2005), as shown in Fig.
 Self-healing composites’ potential applications are mostly connected with safety-critical machines and infrastructures that
may be difficult to access, inspect, maintain and repair, such as off-shore wind turbines, aircrafts and satellites.

10. (4)NANO COMPOSITES ENABLING NOVEL FUNCTIONS
 Many actuation, sensing and other functions discussed above are enabled by the incorporated nanoparticles.
 Functional nano composites are also occasionally referred to as smart composites.
 For example, synthesized Fe3O4-multiwalled carbon nanotubes are a type of smart composite as they can be used to
fabricate intelligent microwave-absorber materials (Lu et al., 2015).
 Nanocapsules containing functional substances may also be regarded as smart composites when they are applied to the
fabrication

11. CARBON FIBER
Carbon fiber is a material made of thin, strong, crystalline carbon filaments that are bonded together in long chains. It's also
known as graphite fiber. Carbon fiber is five times stronger than steel and twice as stiff. It's also lightweight, with some fibers
being thinner than a human hair.
Carbon fiber is made from organic polymers, which are long strings of molecules held together by carbon
atoms. About 90% of carbon fibers are made using the polyacrylonitrile (PAN) process, while the remaining
10% are made using either the rayon or petroleum pitch process.

12. Carbon fiber has many advantages, including:
• High stiffness
• High tensile strength
• High strength to weight ratio
• High chemical resistance
• High-temperature tolerance
• Low thermal expansion

13. Carbon fiber fabrication
Carbon fiber is made from precursors that contain at least 92% carbon. The process of making
carbon fiber involves the following steps:
1. Precursor fiber preparation
2. Oxidization/stabilization
3. Carbonization and graphitization
The precursors and processing conditions determine the properties and structure of the carbon fibers. The two
most important precursors are polyacrylonitrile (PAN) and mesophase pitch (MP).

15. Here are the steps in the carbon fiber manufacturing process:
1. Spinning: Mix PAN with other ingredients to spin into fibers
2. Stabilizing: Chemically alter the fibers to stabilize bonding
3. Carbonizing: Heat the fibers to a very high temperature to form carbon crystals
4. Surface treatment: Treat the surface
5. Sizing: Coat the fibers to protect them from damage during winding or weaving
6. Wound onto spools: The coated fibers are wound onto cylinders called bobbin

16. The process of carbonization involves heating the fibers in an oxygen-free environment at a very high temperature (around
1000 - 3000 degrees Celsius) in an inert atmosphere such as nitrogen. This drives out almost all non-carbon elements from
the fibers, leaving behind almost pure carbon atoms in a crystalline structure. The atoms inside of the fibers vibrate violently,
expelling most of the non-carbon atoms. This leaves a fiber composed of long, tightly inter-locked chains of carbon atoms
with only a few non-carbon atoms remaining.
Carbon fiber has applications in composite materials, textiles, microelectrodes, and flexible heating.