Previous researchers tried to improve the mechanical properties of 3D printed part by adding short or continuous, natural, or nonnatural fibers as the reinforcement for thermosetting or thermoplastic matrix. None of the research found in the literature incorporates continuous natural pineapple leaf fiber as the reinforcement for polylactic acid (PLA) matrix by using 3D printing. The objective of this research is to investigate the tensile strength, the elongation, and the dimensional error of the 3D printed parts made of continuous pineapple leaf fiber-reinforced PLA composite using different values of extrusion temperature and feed rate. The experiment involves 32 factorial design with two replications and, therefore, prints 18 tensile test specimens according to ASTM D638. Based on the result of the experiment, it can be concluded that the use of continuous pineapple leaf fiber as the reinforcement for the PLA matrix increases the tensile strength of the composite. The use of continuous pineapple leaf fiber does not increase the dimensional error value of the composite part beyond the maximum value of the common fused deposition modeling printed part. Moreover, the required time to print the composite part is the same as the required time to print the pure PLA part. However, the elongation of the composite part is lower than the pure PLA part.

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Abstract. In this research, cooling system optimization using thermal energy storage (TES) in shopping center buildings was investigated. Cooling systems in commercial buildings account for up to 50% of their total energy consumption. This incurs high electricity costs related to the tariffs determined by the Indonesian government with the price during peak hours up to twice higher than during off-peak hours. Considering the problem, shifting the use of electrical load away from peak hours is desirable. This may be achieved by using a cooling system with TES. In a TES system, a chiller produces cold water to provide the required cooling load and saves it to a storage tank. Heat loss in the storage tank has to be considered because greater heat loss requires additional chiller capacity and investment costs. Optimization of the cooling system was done by minimizing the combination of chiller capacity, cooling load and heat loss using simplex linear programming. The results showed that up to 20% electricity cost savings can be achieved for a standalone shopping center building.

Due to the different properties of the materials, the fusion welding of dissimilar metals may be difficult. Structural irregularities may form as a result of various phase transformations during welding. Solid-state welding, as opposed to fusion welding, occurs below the melting temperature. As a result of the melting and solidification phenomena that happen in fusion welding, solid-state welding is expected to reduce the potential for phase transformation. This paper describes the use of a rotary friction welding technique to join carbon steel and 304 stainless steel. The purpose of this work is to investigate the characteristics of rotary friction welding (RFW) when joining 304 stainless steel to carbon steels with different carbon contents. Experiments were carried out on the RFW of low- and medium-carbon steels with 304 stainless steel. The investigation was carried out using the Taguchi method of experimental design. The joints’ tensile strengths and microstructures were evaluated. The parameters that had the greatest influence on the tensile strengths of the welding results were identified. The combination of parameters resulting in the greatest tensile strength is also suggested. A microstructural examination of the weldment revealed mechanical mixing and interlocking.

In this research, cooling system optimization using thermal energy storage (TES) in shopping center buildings was investigated. Cooling systems in commercial buildings account for up to 50% of their total energy consumption. This incurs high electricity costs related to the tariffs determined by the Indonesian government with the price during peak hours up to twice higher than during off-peak hours. Considering the problem, shifting the use of electrical load away from peak hours is desirable. This may be achieved by using a cooling system with TES. In a TES system, a chiller produces cold water to provide the required cooling load and saves it to a storage tank. Heat loss in the storage tank has to be considered because greater heat loss requires additional chiller capacity and investment costs. Optimization of the cooling system was done by minimizing the combination of chiller capacity, cooling load and heat loss using simplex linear programming. The results showed that up to 20% electricity cost savings can be achieved for a standalone shopping center building.