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Due to numerous attractive properties, use of composites is in increasing trend. Efforts are
being made to develop new composites securing their useful properties at optimum level for more
demanding applications. The purpose of this project is to optimize the mechanical properties of
composite (polypropylene + wood fiber) using Central Composite Design (CCD) technique.
Accordingly experiments were conducted to develop mathematical models in terms of three process
parameters - composition (percentage of PP and wood fiber), injection pressure (bar), and time
(second) for functional characteristics such as tensile strength and water absorption. Design expert
software was used for convenience to carry out the analysis with a view to identifying the optimum
level of the processing parameters for securing the desirable properties of the composite.
Polymer matrix composites (PMC) have become a substitution material mainly to metallic
components for wider applications in automobile, aerospace, civil structures, sport equipment,
electronics and others for their light weight and high specific strength. The volume and scope of PMC
applications have grown steadily and it has become a material of choice in the 21st century. However,
further development activities are still being undertaken to deploy its tremendously attractive
properties. Though usage of thermosetting resins is common as matrix in PMC, thermoplastic wood
fiber composites also have received considerable attention. The reasons are that the thermoplastic
nature of the composites allows them to be processed using traditional manufacturing methods and
the environmental friendliness leaving a scope of recycling the products or resultant wastes at the end
of useful life. Additionally, PMC is relatively easier to design, fabricate and repair the structures as
endorsed by Kalpakjian & Schamid (2006). Reinforced plastic structures do not have only high
specific strength and stiffness, but also have improved fatigue resistance, greater toughness, and
higher creep resistance.
In shaping the behavior of PMC, the role of matrix materials is very significant. According to
Mazumdar (2002) the matrix must bind the fiber together and transfer the load to the fiber and as a
result the propagation of crack in the fiber slows down. Moreover, a good surface finish with
protection of fibers from mechanical wear and chemical assault can also be achieved. Although wood
fiber would decrease the overall cost, it was not used to improve the properties of the products widely.
A major issue in achieving true reinforcement for wood plastic composite is due to the inherent
incompatibility between the hydrophilic fibers and the hydrophobic polymers which results in poor
adhesion leading to poor ability to transfer stress from the matrix to the reinforcing fibers (Yihua Cui
et al., 2007). Selection of right coupling agents is vital in order to improve the adhesion between wood
fiber and matrix. Variation in fiber orientation can result in unexpected behavior of the material and
Advanced Materials Research Vols. 535-537 (2012) pp 186-189
Online available since 2012/Jun/14 at www.scientific.net
© (2012) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.535-537.186
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