Mechanical Engineering for Society and Industry

Carboxymethyl cellulose films derived from pineapple waste: Fabrication and properties

2025-01-12T14:41:56+00:00

Plastic waste poses a significant environmental challenge due to its non-biodegradable nature, emphasizing the need for sustainable alternatives like bioplastics from natural resources. This study develops and characterizes bioplastic films made from carboxymethyl cellulose (CMC) derived from bacterial cellulose synthesized using pineapple biowaste. Pineapple waste underwent fermentation to produce bacterial cellulose, which was chemically modified into CMC. Films were fabricated using CMC solutions with varying glycerol concentrations (0.5%, 1.0%, 1.5%, and 2.5% v/v). Characterization techniques, including SEM, XRD, FTIR, TGA, mechanical testing, and antibacterial assays, revealed that increasing glycerol concentrations smoothed the film's cross-sectional morphology, reduced crystallinity, and altered functional groups (e.g., new peaks at 870 cm⁻¹ and 935 cm⁻¹ attributed to C–H deformation). TGA indicated a four-stage thermal degradation pattern, with mass loss increasing from 77.2% to 88.4% at 2.5% glycerol, reflecting enhanced plasticization. Mechanical testing showed that the highest glycerol concentration increased film flexibility by 40.7 times while reducing tensile strength by 89.7%. Antibacterial activity against E. coli and S. aureus also improved with glycerol content. These results demonstrate the potential of CMC-based bioplastic films as sustainable packaging materials, offering customizable properties and promoting the value-added use of agricultural waste.

Design, fabrication, and performance testing of an energy storage and return (ESAR) foot prosthesis made of prepreg carbon composite

2025-01-15T00:25:57+00:00

The high demand for prosthetics in Indonesia is not followed by the ability and quality of local production to fulfill the community's needs. There is a lack of comprehensive data regarding the specific challenges encountered by local prosthetic manufacturers in Indonesia, particularly in terms of technological limitations. This study aims to understand the effect of design parameters on the performance of the energy storage and return (ESAR) foot prosthesis prototype in normal walking activities for amputees. Three different designs were created according to commercial products, and a convergence test was conducted to ensure accurate results. Finite element method (FEM) analysis was used to determine the amount of deformation that occurred in each design made when applied with 824 N axial force. The ESAR foot prosthesis prototype made from carbon prepreg was fabricated using an out-of-autoclave method, and the mechanical testing was performed with a compressive test. The results indicated that the optimal design for the ESAR foot prosthesis determined by the decision matrix scoring criteria was Design 3. The final scores for Designs 1, 2, and 3 were 54, 53, and 77, respectively. Design 3 is the easiest to manufacture, has the slightest complexity, and the lightest mass, and undergoes the least deformation during simulation, although it is the least attractive. The study found a significant difference in displacement between the deflections obtained from simulation and experiment. This occurred because the prototype was found to have delamination, which decreased the load-bearing ability of the prototype during compressive testing. Compressive testing on the prototype yielded a deflection of 22.695 mm in heel strike and 18.065 mm in toe-off positions, while FEM analysis showed 16.377 mm and 3.912 mm. Therefore, strict quality control is essential, especially when using materials such as carbon prepreg, which are prone to delamination if not properly processed.

The effect of ignition timing on engine performance in a laser ignition engine: A CFD study

2025-01-15T00:35:11+00:00

As a result of the high-power output, low fuel consumption, and low emissions expected from internal combustion engines, new engine technologies continue to be developed. Laser ignition systems are a solution to these expectations with the advantages they offer. Experimental and numerical studies related to laser ignition systems are accelerating today. In this study, an internal combustion engine was simulated with the spark and laser ignition systems, and the changes in engine performance for different ignition timings were investigated comparatively. ANSYS Fluent 2021 R1 software was used in the dynamic CFD study in which the entire engine cycle was analysed. Analyses were carried out at constant engine speed with an iso-octane+air mixture. Critical parameters such as pressure, volume, and temperature changes, power, torque, IMEP, MPRR, peak pressure, HRR, CHRR, start of combustion, and combustion duration were evaluated for both ignition systems. As a result of the study, optimum performance values were obtained at 680 °CA ignition timing with laser ignition system. At this ignition timing, power, torque, IMEP, MPRR, and peak pressure values were determined as 16.4302 kW, 62.7635 Nm, 14.1743 bar, 2.4665 bar/°CA, and 61.5611 bar, respectively. The laser ignition system increased engine performance, and smoother and knock-free combustion occurred. At optimum ignition timing, combustion duration was shortened, and in-cylinder temperatures decreased. The findings show that the laser ignition system will contribute to engine development studies by positively affecting engine and combustion performance.

Mechanical properties of biocomposite from polylactic acid and natural fiber and its application: A Review study

2025-02-03T08:33:59+00:00

In the past decade, the development of biocomposite materials has attracted much attention due to the growing concerns about petroleum-based natural resource depletion and pollution. Among the various biocomposite materials, polylactic acid (PLA) is one of the most widely produced and ideal for use in commercial products. The manufacture of PLA biocomposites with natural fiber reinforcement as an alternative material that replaces synthetic materials is widely researched. The different types of natural fiber sources used in the incorporation of matrix and fibers are very important as they affect the mechanical properties of the biocomposites. In addition, PLA-based biocomposites can be produced by a wide variety of methods that can be found in various commercializations. This study aims to present the recent developments and studies carried out on the development of PLA-based natural fiber biocomposites over the past few years. This study discusses PLA biocomposite research related to their potential, mechanical properties, some manufacturing processes, applications, challenges, and prospects.