Influence of sampling area and extraction method on the thermal, physical and mechanical properties of Cameroonian Ananas comosus leaf fibers.

The wide dispersion of the properties of plant fiber bundles further limits their use. In this study, manual and retting methods were used to extract fiber bundles from the available and underutilized Ananas comosus (AC) leaf waste in Cameroon. These fibers were sampled in three zones: base, middle and head. The fibers extracted by retting in the different zones were found to have better thermal stability. A 2.5% solution of sodium hypochlorite was used for bleaching the various pineapple fibers. Density, fineness, functional groups, mechanical properties, water absorption and morphology of different fibers were characterized. Density and fineness decreased from the head to the base of the leaf and were lower for manually obtained fiber bundles. The peaks of the infrared spectra associated with the functional groups of the pineapple fibers change very little along with the leaf but are clearly more pronounced for the fibers extracted manually. Fibers in the middle of the leaf have been found to have slightly better mechanical and water absorption properties. All fiber bundles can rapidly absorb water following simple exponential kinetics. Bleaching partially removes non-cellulosic materials from the fibers with a transverse shrinkage effect, which improves their fineness, density and hydrophilic function. Unfortunately, it reduces their tensile strength and fracture toughness. These results show that the whole leaf can be used without restriction to extract manually or by retting the fiber bundles intended for the manufacture of textiles and composites. Furthermore, bleaching with sodium hypochlorite seems ineffective due to fiber degradation.

The effects of multiple drilling of a bone with the same drill bit: thermal and force analysis.

Repeated use of the same drill bit during drilling wears off the cutting edges, which can lead to a significant increase in heat as a result of friction, which is harmful to a bone above 55 °C. Few previous studies have examined the effects of using the same drill bit several times, on temperature. The objective of this study was to determine the effect of each drilling on temperature and force. 72 trials were performed. A total of 24 stainless steel drill bits of ∅3.2 mm were used to drill bovine bone samples. Each drill bit was used at least 3 times. T thermocouples were used to measure temperatures during each drilling test. Possible correlations of cutting parameters were studied. Tests were performed on a test rig measuring forces and temperatures during drilling. Effects of spindle speed (N), feed rate (Vf), and several trials (E) on temperature and forces were measured. Images of the drill bits were analyzed by digital microscopy before and after the drilling series for signs of wear. Temperatures increased significantly from E1 to E3. They decreased moderately with Vf. The best cutting conditions were at N = 200 rpm for Vf = 60 mm/min and N = 100 rpm for Vf = 30 mm/min drilling. At N > 200 rpm, they were very high. Temperature rise is significantly related to number of drilling (E), spindle speed (N), and inversely to feed rate (Vf). Analysis of images by digital microscopy confirmed drill bits wearing off, following the number of trials.