BEHAVIOUR OF HEMP AND SISAL FIBER REINFORCED POLYPROPYLENE COMPOSITES
The use of vegetal fibres in thermoplastic matrix is increasing mainly because of their opportunity to recycle the structures. An another advantage is to provide materials for developing countries were these fibers are abundant. Nowadays, a lot of studies are more focused on the fibers to understand their microstructure and to establish their mechanical properties [1,2]. One of the main results is to see that these properties exibit a large uncertainty. The main question is to know if this uncetainty propagates through the different scales upto the structures providing stochastic proporties at the macroscale. The goal of this work is to carry out several tensile tests on coupons to establish the uncertainty of the investigated materials taking into account the crosshead speed.
Quality of chemically modified hemp fibers.
Hemp fibers are very interesting natural material for textile and technical applications now. Applying hemp fibers to the apparel sector requires improved quality fibers. In this paper, hemp fibers were modified with sodium hydroxide solutions (5% and 18% w/v), at room and boiling temperature, for different periods of time, and both under tension and slack, in order to partially extract noncellulosic substances, and separate the fiber bundles. The quality of hemp fibers was characterised by determining their chemical composition, fineness, mechanical and sorption properties. The modified hemp fibers were finer, with lower content of lignin, increased flexibility, and in some cases tensile properties were improved. An original method for evaluation of tensile properties of hemp fibers was developed.
Effects of Equipment Dimensions on Liquid Mixing Time of Bubble Column with Draft Tube
The liquid mixing time of a bubble column with a draft tube is experimentally studied. The diameter and height of the column, the diameter and length of the draft tube, and the mode of sparging gas were changed and the liquid mixing time was measured.The lengths of bottom and top clearances have significant effects on the liquid mixing time. The liquid mixing time increases with increasing column aspect ratio of height to diameter. The liquid mixing time of the bubble column with a draft tube is longer than that of a standard bubble column when the column aspect ratio is relatively high. The liquid mixing time has a minimum when the diameter ratio of draft tube to column is 0.5 to 0.6. These effects of equipment dimensions are expressed by an equation. In the experiment using different solutions, the liquid mixing time becomes shorter with increasing liquid surface tension, or with increasing liquid viscosity.