Senthilkumar Krishnasamy - Natural Fiber-Reinforced Composites: Thermal Properties and Applications

Chandrasekar Muthukumar

Hindustan Institute of Technology & Science, Department of Aeronautical Engineering, Kelambakkam, Chennai 603103, Tamilnadu, India

King Mongkut's University of Technology North Bangkok, Center of Innovation in Design and Engineering for Manufacturing (CoI-DEM), 1518 Wongsawang Road, Bangsue, Bangkok 10800, Thailand

Kalasalingam Academy of Research and Education, Department of Mechanical Engineering, Krishnankoil 626126, Tamil Nadu, India

King Mongkut's University of Technology North Bangkok, The Sirindhorn International Thai-German Graduate School of Engineering (TGGS), Department of Materials and Production Engineering, 1518 Wongsawang Road, Bangsue, Bangkok 10800, Thailand

Hybrid composite is fabricated by adding two or more fibers into a single polymer system ]:

1. Fiber length
2. Fiber loading
3. Fiber orientation
4. Fiber layer sequence
5. Fiber/matrix interfacial bonding
6. Failure strain of fiber

The hybrid effect is termed as an apparent synergistic improvement of properties due to different fibers in a single matrix system. The selection of fibers and their properties is of main importance to achieve the enhanced properties for the hybrid composites. Besides the physical, chemical, and mechanical stabilities of fiber, the matrix system also defines the strength of the hybrid composites. The different types of hybrid composites are characterized as follows []:

1. Tow by tow: the fibers are mixed up randomly or regularly.
2. Sandwich hybrid composites: one material is sandwiched between two different layers.
3. Inter-ply or laminated: two or more fiber layers are alternatively stacked regularly.
4. Intimately mixed fibers: various types of fibers are mixed up randomly.

Though the hybrid composites have many advantages, the prime challenges are replacing the synthetic fiber-reinforced composites using biocomposites. Biocomposites exhibit functional and structural stability during storage and degrade upon disposal into the environment. Engineered natural fiber is one of the exciting concepts to obtain the enhanced strength in the biocomposites, which involves the blending of the leaf and stem fibers. The correct blending of these two fibers exhibits optimum balance in mechanical properties, resulting in balanced stiffnesstoughness properties [].

The mechanical and physical characteristics of the natural fiber are influenced by many factors: (i) maturity of the plant fiber, (ii) harvesting time and region, (iii) soil condition, (iv) rain, (v) sun, etc. Since the natural fibers are nonabrasive and hypoallergenic, they could be processed efficiently. Amongst the various properties of natural fibers, the low density and the cellular structure allow them to exhibit better thermal properties. However, the amorphous hemicellulose on the fiber surface can be a potential threat to the better interfacial bonding between the matrix and the fiber, thereby reducing the properties. Hence, the mechanical and thermal properties of the biocomposites could be further enhanced through chemical treatments ).