Impact strength, microstructure, and water absorption properties of kenaf/polyethylene terephthalate (PET) fiber-reinfor
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Natural fiber composites are becoming more attractive for applications as energy absorbers in the automotive industry despite their high moisture absorption characteristics. The main objective of this paper is to study the impact strength and moisture absorption properties of long fiber and short fiber hybrid composites using a kenaf/polyethylene terephthalate fiber reinforced in the polyoxymethylene matrix. The results obtained from the impact test gave 10.8 J/cm for the longer fiber hybrid composites, which is higher compared to 8.0 J/cm obtained for the short fiber hybrid composites due to less fiber pullout from the matrix. A moisture content of 0.92% and percentage water absorption of 6.77% were obtained for the long fiber composite due to poor interfacial adhesion between the fiber and the matrix. A high void content of 0.52% and porosity of 1.21% also accounted for high water and moisture absorption of the long fiber hybrid composite.
I. INTRODUCTION
The mechanical testing of most composite materials is mainly concerned with high elastic modulus and strength. High strength is not sufficient enough for some composites to withstand severe stress in operation due to their brittle behavior. One significant property is the ability to absorb energy for structural applications.1 The development of natural fiber composite materials is significant in the design of structural parts for automotive applications. The aim is to achieve lightweight, low production cost, and eventually reduced fuel consumption. Structural parts of vehicles such as front and rear bumpers are designed as energy absorbers to withstand an impact of 8 km/h without damage in low speed collision.2 The choice of using a natural fiber and a thermoplastic fiber embedded in a thermoplastic matrix will not only produce the structural parts but also give the final parts its unique style and dimensional tolerance. Apart from ecological advantages, natural fibers have good mechanical properties combined with low specific gravity. In considering industrial safety, natural fibers do not cause skin irritation or allergic reactions compared with synthetic fibers.3 The effect of reinforcing filler loading on the impact strength of a wood plastic composite was investigated.4 The results of the notched impact test according to ASTM D256 confirmed that increasing the reinforcing filler loading reduces the flexural strength, tensile strength, impact a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2013.210 2142
J. Mater. Res., Vol. 28, No. 16, Aug 28, 2013
http://journals.cambridge.org
Downloaded: 21 Jun 2014
strength, and elongation at break of the composite. The poor interfacial bonding between the fiber and the matrix caused the initiation of microcracks at the point of contact, which then propagates into the matrix thereby reducing the impact strength of the composite. The determination of the radial impact strength of fiber-reinforced composite tubes using a drop hammer was also carried out.5 Glass fiber-reinforced plastics were tested
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