Biomedical Engineering Reference
In-Depth Information
Chapter 4
maize-Natural Fiber as reinforcement with
Polymers for structural applications
Saravana D. Bavan and Mohan G. C. Kumar
iNtroduCtioN
Nature has provided an immense source of fibers to the human kind, and among them
plant based fibers are in great importance because these plant natural fibers are available
in abundance which are able to replace the synthetic fibers in the present composite
field due to their low density, non-abrasive, good-insulation properties, recyclability,
biodegradable, and other mechanical properties (Jacob and Thomas, 2008; Mohanty
et al., 2001, 2005). The above mentioned properties make them superior over the syn-
thetic fibers or man-made fibers. Natural fibers are classified as plant fibers or veg-
etable fibers, animal fibers, and mineral fibers. Plant-based or vegetable natural fibers
are lignocellulosic, consisting of cellulose micro fibrils in an amorphous matrix of
lignin and hemicellulose (Sanadi et al., 1997). The fiber structure is hollow, laminated,
with molecular layers and an integrated matrix. Fiber structure and properties of some
agricultural residues is shown in Table1 . Natural fiber reinforced polymer composite
materials are an important class of engineering materials because they have better
mechanical properties and ease of fabrication. Thermal properties of natural fiber re-
inforced polyester composites were carried out (Idicula et al., 2006) and indicated that
the chemical treatment of the fibers reduces the composite thermal contact resistance.
Thermosetting resins are used today with plant fiber for panels suitable for inner
door panels for the automotive industry and other applications in structures. The costs
of these resins are low compared to thermoplastic resins and also the properties of the
resin are well suited for structural application (Wool and Sun, 2005). Recently lot of
research has been carried out on natural fibers using resin transfer molding (RTM) as a
processing method of composites. Dynamic mechanical properties of sisal based natu-
ral fibers reinforced with polyester were investigated using RTM (Sreekumar, 2009,
2009a). Vacuum assisted resin transfer molding (VARTM) techniques have been de-
veloped for fabricating small and large components but mainly for complex shapes.
It also gives good surface finish to the particular part. It is best suited for low cost
components of complex part which should be pressurized by external source. It uses
atmospheric pressure as a clamp to hold the laminates together.
Unsaturated polyester resins are the cheapest and best material in the compos-
ites industry and represent approximately 75% of the total resins used. Thermoset
polyesters are produced by the condensation polymerization of dicarboxylic acids and
difunctional alcohols (glycols). In addition, unsaturated polyesters contain an unsatu-
rated material, such as maleic anhydride or fumaric acid, as part of the dicarboxylic
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