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 specific properties and availability of banana pseudo-trunk fibers make them a promising alternative for the development of green composites. However, the wide dispersion of their properties can hinder their use. In this study, the influence of the sampling area of the banana pseudo-trunk on the physical and mechanical properties of the fibers was evaluated. Prior to retting, the trunk was sampled longitudinally (bottom, middle and top) and transversely (periphery, intermediate and heart). Gravimetric tests were carried out and revealed variations in water absorption (347.1–517.4%), density (0.92–1.45 g.cm⁻³) and linear mass (25 -34tex). Tensile tests were also performed and showed a significant effect of fiber location on Young’s modulus (6.60–34.6GPa), tensile strength (91-350MPa) and elongation at the break (0.9–2.6%). Due to diameter scatter, variations of 42% were found for fibers in the same area. In a region, the physical properties increase from the periphery to the core, and the mechanical properties decrease in the same direction, except for elongation. The results of this study showed good agreement with those of other natural fiber types. However, we recommend the peripheral areas of the pseudo-trunk to extract reinforcing fibers from composites because of their low density (0.9 g.cm⁻³) and their high stiffness (34GPa).

Stability is a key indicator of the efficiency of the gas metal arc welding operation, and it is linked to other quality indicators like spattering and weld formation. This study describes methods of assessing arc stability for selected gas metal arc welding (GMAW) conditions. It focuses on stability characterization and defines the relationship between process stability and influencing factors. Welding tests were performed using two selected transfer modes the spray and the pulse transfer modes to characterize stability and develop processes further for better overall performance. This scope of parameters was selected to simulate certain range of stability behavior, so it was possible to analyze the factors correlated to stability, their relevance in influencing stability, and consequently to define a calculation algorithm for the determination of stability. Also, stability was calculated and scored based on two scoring indices. With a higher voltage, disturbance levels were noticed to reduce as in the case of 29 V, 31.5 V, and 32.5 V with 32.5 V showing better stability to spattering, smoothness, repeatability, and regularity of the process. Actual values of positive and negative voltage peaks, voltage amplitudes, and their average values and standard deviations in selected analyzed time showed to be relevant indicators to characterize stability of the process. Variations of indicated voltage signals related to explosions showed to have complex patterns in terms of their waveforms. So, all these were analyzed step by step and consequently selected for characterization in the welding conditions that were selected in the scope of this study.