Papers by Author: Jae Kyoo Lim

Abstract: This paper investigated the fracture behavior of the unavoidable breakage of carbon fibers and fiber orientation of short carbon fiber reinforced polycarbonate composite in injection process. In this experiment, short carbon fiber mixed compound of 1mm, 3mm, 5mm, 7mm length with 10wt.%, 15wt.%, 20wt.% in polycarbonate for injection molding were produced through the extruder. The dumbbell specimens for tensile evaluation were made by injection molding. The parent specimens were made by double gate method, the weld specimens were made by single gate method which was controlled by inserting a stopper through the runner of the mold cavity. Short carbon fiber reinforced PC composite was evaluated by micro-CT with regard to the particle size of short fiber with a diversified quantitative analysis through entire process of the injection process in composite. The quantitative distribution of fiber orientation was also examined by micro-CT with regard to normal direction or anisotropy. Weld line of short carbon fibers reinforced PC composite weaken the bonding strength by 50% compared to parent materials because the weld line is composed with concentrated anisotropy orientation of short carbon fiber in weld line. Evaluation of the mechanical properties of the injection specimens group was utilized by universal tensile strength tester. In addition, fracture surface of parent and weld materials was investigated by a SEM.

Abstract: As we secure sufficient space to distribute power generation equipment of solar energy, there will be no shaded area, but for the limited space, we can find temporaryshaded area surely for a few moments or a few hours .For the fixed type which are used to most roof solar power plant, side beam is projected for certain period of time before and after sunset, it would be affected to electric generation efficiency, so we researched to solve this phenomena using concave and convex mirror. For basic principle, when module is positioned at shaded area and time, it can deliver to be spread toward module to be accumulatedsunshine with concave mirror and reflected with convex mirror. For net energy which is obtained from sunlight, it produced 223W/day and it produced 207W/dayusing reflect mirror, we can get result which we can get similar amount of power energy only with reflect mirror.It shows that the production by direct light has increase of 8% more than production by reflected light.

Abstract: Mechatronics is an integration technology which is the mutual penetration of mechanical technology, microelectronic technology and information technology and the inevitable development trend of electromechanical industry. This paper describes the overview, core technology and main application fields of mechatronics technology and points out its development trend.

Abstract: Green chemistry approach (hydrothermal process) is utilized for grafting maleic anhydride (MA) into linear low density polyethylene (LLDPE), thereby enhancing the compatiblility of the latter in its blend with polylactic acid (PLA). The grafting of MA into LLDPE is confirmed by Fourier Transform-Infrared Spectroscopy (FT-IR) analysis. LLDPE-g-MA content in PLA matrix is varied as 4% wt., 8% wt. and 12% wt. when preparing glass fiber reinforced PLA/LLDPE-g-MA thermoplastic composite via hot pressing. Single Edge Notch Bend (SENB) specimens have been prepared from the composites and three point bend test was performed.The load-displacement plot of the test results indicates that the ductility index (DI) increased for the samples with increased LLDPE-g-MA content. The observation of the fractured surface of specimens in Scanning Electron Microscope (SEM) suggests that the improved DI value is because of the increased matrix ductility owing to the plasticizing effect of the LLDPE-g-MAH inclusion.

Abstract: The delamination and fibers pull out have been the main factors failure application of natural fibers in various engineering fields. To address these problems, particles reinforced composites are the promising candidate. The present paper investigates on vegetal particles (date palm seed particles/DPSp) and applies it as composites material reinforced unsaturated polyester (USP). The influence of alkali treatment on the surface morphology and structure of DPSp was investigated. They investigated by SEM and Energy Dispersive Spectroscopy (EDS) mapping. The water absorption results showed directly proportion with the particles loading as the relative increases were 0.645% and 7.345% for 10 wt% and 40 wt% of DPSp content, respectively. In addition, the water absorption ability of the composites showed low value comparing with many natural fibers. In addition, the fracture toughness of the composites was studied. Overall, addition of the proposed DPSp particles may be opens a new avenue to exploit the utilized natural cheap material to produce a green composite.

Abstract: In this research, short jute fiber reinforced polylactide composite, unidirectional long fiber reinforced polylactide composite and a sandwich structure polylactide composite were fabricated and the mechanical properties were tested. The mechanical properties of the fabricated composites were compared with those of a prototype spare tyre compartment cover of a passenger car. Tensile strength and flexural strength of all the composites are higher than those of the spare tyre compartment cover. The results show that the polylactide composites are applicable to car interior plates.

Abstract: Failure strength evaluation on resistance welding mixed adhesive bonding was studied. Tensile-shear tests were carried out with the single-lap specimen, using both resistance welding and adhesive bonding. Peel tests were also carried out with DCB specimen. Composites were manufactured using the polyester as a matrix and bamboo natural fiber layer as a reinforcement. Adhesive bond, having bonding strength that remains unaffected by heat at resistance welding, were selected. Generally, adhesive bond require a long curing time and have little strength before hardening. Resistance welding helps weakness of adhesive bond both curing time and peel strength. And the spew fillet of adhesive bonding also helps to release stress intensity of edge of joining. The failure mechanism was discussed in order to explain higher peel and tensile-shear strength of resistance welding mixed adhesive bonding.

Abstract: Structure adhesive bonding method is widely used in the industry because it is possible to joint complex shape and dissimilar materials. Especially in the car industry, requests of lightweight car have adhesive bonding method be applied in the many parts. Also it is possible for stress to distribute uniformly through the adhesive layer, and stress concentration is released. Since strength, stiffness durability is much better, this method is determined as the technique replaced weld defect. But, it has much shorter history then other joint method such as spot weld and mechanical joint method. Evaluation of strength and durability is not established. As the fundamental research of design of adhesive bonding joints, considers over-lap length, adhesive thickness, surface treatment and environment which affect strength and durability of single-lap joints. In this research, a real part of bus folding door was used and tested to compare durability of spot welding and adhesive bonding.

Abstract: This research is concerned with a study of failure strength of natural fiber composite. Tensile-shear tests were carried out with the single-lap resistance welded joined specimens consisting of composite materials. Composite materials were manufactured using the polyester as a matrix and bamboo natural fiber layer as a reinforcement. Two types of specimen with different reinforcement positions were tested to evaluate the failure strength of natural fiber reinforced composite resistance welded joined specimens. The test results were presented by tensile-shear strength. The failure mechanism was discussed in order to explain the lower tensile-shear strength of composite and position of bamboo natural fiber layer on the failure strength properties were explained

Abstract: This research was concerned with study of fracture strength of adhesive-lap-joined composites. The tensile and peel tests were carried out with specimens manufactured hybrid stacked composites, because the orientation of fiber and the interfacial fracture between the matrix and the reinforcement had influence on failure strength of composites. Bamboo natural fiber layer was located between polyester layers. The objective of this study was to evaluate the effect of fiber orientation on failure strength properties of composites. The test results were presented by load-displacement graph and finite element analysis. As a result, the load-directional orientation and the thinner thickness of bamboo natural fiber layer have a good effect on peel and tensile-shear strength and failure shape of adhesive-joined hybrid stacked composite.