Abstract:
This thesis developed composites from the benefit of using short and 2D woven sisal fibres as reinforcing fibres in polyethylene and unsaturated polyester. The effects of fibre surface treatment, fibre content and fibre orientation on mechanical properties and morphology of the composites were investigated. Sisal fibres were treated by alkalization in 1 mol (4 wt.%) NaOH at 60 C for 1-5 h and novel treated with NaOH in ultrasonic field for 30-90 min. Mechanical properties and morphology showed that sisal fibres treated with NaOH and ultrasonic field were cleaner and smoother with less treatment time than treated by NaOH only. Composites of short sisal fibres treated with NaOH for 1-5 h were fabricated with polyethylene by hot press molding. Mechanical testing was carried out according to ASTM standard. Morphology of the composite was observed by scanning electron microscope (SEM). Results informed that composites of short sisal fibres treated in NaOH for 5 h yielded the highest values of tensile strength. Next, composites with sandwich structure were fabricated using 2D woven fibres and unsaturated polyester by hand lay-up process. The composites with 15 wt.% (3 layers) of 2D sisal fibres obtained the maximum tensile, flexural and impact strength. After that, the composites were prepared with various 2D woven fibre orientations by using 3 layers of the woven fibres. The first and the third layers were oriented at 0 while the second layer was laid at 0 (0/0/0/), 30 (0/30/0), 45 (0/45/0) and 60 (0/60/0). Properties of the composites with treated fibres were higher than the composites with untreated fibres. SEM photographs indicated that treated fibres were good adhered with the matrix, which would improve mechanical properties of the composites. It can be noted that the fibre orientation was significantly effect on mechanical performance of the composites. It was found that the composites with the fibre oriented at (0/0/0) showed the highest in tensile strength. On the other hand, the fibres oriented at (0/60/0) provided the optimum values of flexural and impact strength in the composites.