Investigation of Impact Behaviour of Sisal Fiber Reinforced Phenol Formaldehyde Composites

Short Sisal fiber reinforced Phenol Formaldehyde resin composites are prepared with varied fiber lengths (5 mm and 10 mm) and for varied weight fraction (20%, 25% and 30%) of the fibers. Here in this work, Sisal fiber is used as reinforcement. Since it is abundantly available in nature and majority of it is getting wasted without being used as reinforcement in engineering applications. Over the last thirty years composite materials, plastics and ceramics have been the dominant emerging materials. The 10 mm fiber length reinforced composite shown improved mechanical properties than 5 mm fiber length reinforced composite. Increase in impact strength is seen when the fiber content in the composite is increased from 20% to 25% and 25% to 30%. The fiber strength, for different fiber lengths and fiber volume fraction, the work of fracture is proportional to the fiber length and fiber volume fraction. Although results show increment in impact strength with fiber volume fraction, proportionality is not demonstrated. This suggests that there are other mechanisms that affect the impact strength of the composites. Crack propagation is the predominant toughening mechanism in notched impact test. Improvement in impact strength characterizes that fibers as stress transferring medium are able to absorb impact energy effectively. Good interaction with crack increases the energy needed for further crack formation and propagation. The exceptional case could be due to low fiber content and relatively short fiber length so that the energy is not dissipated effectively. Weak interfacial bonding of natural fibers is mainly due to incompatibility of hydrophobic matrix and hydrophilic fiber. High moisture absorption causes dimensional changes of natural fibers as well.