Biomedical Engineering Reference
In-Depth Information
Chapter 7
silk Fibers and their unidirectional Polymer
Composites
Mansur Ahmed, Md Saiful Islam, Qumrul Ahsan, and Md Mainul Islam
iNtroduCtioN
Natural fiber reinforced polymer composites have gained their popularity in the com-
posite research because of versatility and diversified nature of their applications (Gay
et al., 2003). This is due to a range of potential advantages of natural fibers, espe-
cially with regard to their environmental performance. Natural fibers are renewable
resources and even when their composite wastes are incinerated, they do not cause net
emission of carbon dioxide to the environment. They are inherently biodegradable,
which may be beneficial (Aquino et al., 2007; Singleton et al., 2003; Verpoest et al.,
2010). Among all the natural reinforcing fibrous materials, silk appears to be a promis-
ing fiber due to its high toughness and aspect ratio in comparison with other natural
reinforcements. Moreover, the mechanical properties of silk fibers consist of a combi-
nation of high strength, extensibility, and compressibility. On the other hand, maleic
anhydride grafted polypropylene (MAPP) and commercial grade polypropylene (PP)
are commonly used matrices for fiber-reinforced composites due to their good interfa-
cial bonding properties (Karmarkar et al., 2007; Wambua et al., 2003).
In this chapter, both raw and alkali treated silk fibers are taken into consideration
to characterize their properties first. The specific objective is to determine the modulus
and strain to failure of the single silk fiber. Other aims of this work are to fabricate the
unidirectional silk fiber reinforced polymer (MAPP and commercial grade PP) matrix
composites by varying fiber volume fraction and to determine their mechanical prop-
erties such as tensile strength, flexure strength, impact strength, and hardness.
materials aNd methodoloGy
Collection of silk Fiber and Polypropylene resin
Silk fibers were collected from Sapura Silk Industries, Rajshahi, Bangladesh. Two
types of silk--raw silk and alkali treated silk fibers were collected. Commercial grade
PP resin was collected from a local chemical manufacturer and distributor. The MAPP
was collected from Belgium.
specimen Preparation for tensile testing of Fibers
At first, single silk fibers (both raw and alkali treated silk) were chosen randomly,
which were cut down a particular length at prior. The diameters of single fibers were
measured using Scanning Electron Microscope (SEM). The fibers were stacked be-
tween two-paper frame, as shown in
Figure 1,
to conform good gripping to the clamps
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