A study on the potential of sugarcane fibers/polyester composite for tribological applications

The tribo-potential of sugarcane fibre reinforcement in the thermoset polymers for enhancing the adhesive wear resistance has not been explored so far. Hence, the present work aims to explore the possibility of using this natural fibre to reinforce polyester and thus opens a new way to implement locally available inexpensive fibres and produce a new candidate tribo-material for bearing applications. Sugarcane fibre/polyester (SCRP) and glass fibre/polyester (GRP) composites (with chopped fibres of 1, 5, 10 mm length randomly distributed and unidirectional mat fibres) were prepared using compression mould and hand-lay-up techniques. Friction coefficients and wear rates of SCRP and GRP composites were determined under dry sliding contact conditions in parallel and anti-parallel orientations and subjected to different operating parameters such as load, speed and test duration. Results of friction and wear proved that SCRP composite is a promising composite which can be a competitive to GRP composite. In the case of chopped sugarcane/polyester (C-SCRP) composite, very smooth patches of polymer film (protective layer) due to plastic deformation shielded the surface of C-SCRP composite pin from damage by the metallic asperities and thereby contributed to the higher wear resistance. Furthermore, this layer provided enhancement to the bonding of SCFs fibre with matrix. In contrast C-GRP composite produced broken hard particles of GF at the interface which acted as a third body and restrained the formation of such protective layer. Wear resistance of C-SCRP composite increased significantly with increasing load but decreased drastically for C-GRP composite. In addition, wear rate of C-SCRP composite decreased by (20-50%) when the fibre length increased from 1 to 5 mm. With further increase in the fibre length to 10 mm, the wear rate was no longer decreased instead increased drastically by 40-70%. Besides C-SCRP composite gave friction coefficient of the same order as C-GRP composite. Unidirectional sugarcane/polyester (U-SCRP) composite showed lowest wear resistance when fibre was oriented parallel to sliding direction. But when this composite tested in AP-O, wear resistance was almost the same as the CM-GRP composite. Moreover, the U-SCRP composite exhibited lowest friction coefficient when tested in AP-O and highest when tested in P-O, suggesting that reinforcing polyester with sugarcane fibre (SCF) in AP-O can be a competitive to glass fibre. In conclusion, glass fibres have negative impact on the formation of polymer film and responsible for the observed discontinuous (ruptured) film for C-GRP composite. In other words, the back transfer polymer film formed at the interface managed to survive in the case of using SCF but in the case of GF, the effect of impact-type repeated loading caused by hard asperities and broken particles of glass fibre unstable the formation of such protective layers together with increased debonding and fractured fibre resulted in higher wear rate of C-GRP composite. Finally, microscopic observation evidenced that the SCF has the ability to have a fairly good bonding with the polyester matrix. This in turn made the separation of fibre from the composite more difficult and hence contributed to improvement of wear resistance for C-SCRP composite compared to C-GRP composite. In contrary, the bonding between GFs and the matrix for C-GRP composite was not that strong and the fibres were easily debonding. (c) 2007 Elsevier B.V. All rights reserved.