Showing papers by "Dai Gil Lee published in 2000"
TL;DR: In this article, the dependence of the lap shear strength of a co-cured single lap joint on the bonding parameters was investigated by experimental analysis, and the failure mechanism of the co cured single lap joints was partially cohesive failure.
Abstract: In this paper, the lap shear strength of a co-cured single lap joint subjected to a tensile load was investigated by experimental analysis. Co-cured joint specimens with several different bonding parameters such as bond length, surface roughness, and stacking sequence of the composite laminate were fabricated and tested. The dependence of the lap shear strength of the co-cured joint on the bonding parameters was investigated from the experimental results. The failure mechanism of the co-cured single lap joint was partially cohesive failure. The lap shear strength of the co-cured single lap joint was significantly affected by the bond length and the stacking sequence of the composite laminate. However, the effect of surface roughness on the lap shear strength of the co-cured single lap joint was not so significant.
42 citations
TL;DR: In this article, the effect of surface roughness on the fatigue life of adhesively bonded tubular single lap joints was investigated analytically and experimentally by a fatigue torsion test.
Abstract: Since the surface roughness of adherends greatly affects the strength of adhesively bonded joints, the effect of surface roughness on the fatigue life of adhesively bonded tubular single lap joints was investigated analytically and experimentally by a fatigue torsion test. The stiffness of the interfacial layer between the adherends and the adhesive was modelled as a normal statistical distribution function of the surface roughness of the adherends. From the investigation, it was found that the optimum surface roughness of the adherends for the fatigue strength of tubular single lap joints was dependent on the bond thickness and applied load.
40 citations
TL;DR: The tensile and compressive tests of glass-epoxy composites with 1-200 s−1 strain rates during automobile crash accidents were performed in order to measure the strength variation with respect to strain rate as discussed by the authors.
36 citations
TL;DR: In this paper, an optimum design method for co-cured steel-composite tubular single lap joints under axial load is proposed based on a failure model which incorporates the nonlinear mechanical behavior of the steel adherend and the failure mode of joints such as composite adherend failure and steel fail.
Abstract: In this paper, an optimum design method for co-cured steel-composite tubular single lap joints under axial load is proposed based on a failure model which incorporates the nonlinear mechanical behavior of the steel adherend and the failure mode of joints such as composite adherend failure and steel adherend failure. The design parameters considered were the test temperature, the stacking sequence of the composite adherends, the thickness ratio of the steel adherend to the composite adherend, and the existence of scarf in the steel adherend. Stress analysis of the cocured steel-composite tubular single lap joints was performed considering the nonlinear mechanical behavior of the steel adherend, and the fabrication residual thermal stress and thermal degradation of the composite adherend. The method developed may be employed in the joining of hybrid composite structures such as golf clubs and automotive composite propeller shafts in which a carbon/epoxy shaft has normally been bonded to a metal shaft with e...
34 citations
TL;DR: In this article, the grinding characteristics of composite hollow flexible shafts were investigated experimentally and analytically with respect to stacking sequence and stiffness of carbon fiber epoxy hollow composite shafts.
Abstract: Since carbon fiber epoxy composite materials have excellent structural properties due to their high specific strength, high modulus, high damping and low thermal expansion, composite hollow shafts have been widely used for power transmission shafts for motor vehicles, spindles for machine tools, and rollers for thin film processing. However, the surfaces of molded composite shafts are not always satisfactory for precise mechanical elements, which often requires turning or grinding of surfaces.The machining characteristics of composite hollow shafts are different from those of conventional metal hollow shafts because composite hollow shafts have anisotropic inhomogeneous material characteristics.In this paper, the grinding characteristics of composite hollow flexible shafts were investigated experimentally and analytically with respect to stacking sequence and stiffness of carbon fiber epoxy hollow composite shafts.
25 citations
TL;DR: In this article, a high speed aerostatic spindle was designed and manufactured using high modulus carbon fiber-epoxy composite material for the first time, which has excellent properties for structures, owing to its high specific modulus, high damping and low thermal expansion.
Abstract: Recently, aerostatic bearing systems are widely used in various fields in which high precision and high speed are required because of their advantages such as low friction and low heat generation However, the aerostatic bearing systems have low radial and axial stiffnesses and poor damping properties due to low viscosity of air, and consequently have a low starting value of whirl vibration if heavy metallic spindles are employedAs the carbon fiber-epoxy composite material has excellent properties for structures, owing to its high specific modulus, high damping and low thermal expansion, the vibrational and thermal characteristics as well as the starting value of the whirl of spindles will be improved if the proper design and manufacturing methods for the composite spindle are developedIn this paper, a high speed aerostatic spindle was designed and manufactured using high modulus carbon fiber-epoxy composite material for the first time The design method of the composite spindle and joining method of th
17 citations
TL;DR: In this article, the tensile load capability of co-cured joints composed of carbon fiber epoxy composite and steel adherends was experimentally investigated with respect to the stacking sequence of the composite and the environmental temperature.
Abstract: Co-cured joints composed of composite and steel structures are realized by the excess resin extracted during cure of composite prepreg and the coupling pressure due to residual thermal stresses generated by the difference of coefficients of thermal expansion between the two materials. Although the excess resin from the composite prepreg is less dependent on the environmental temperature compared to conventional epoxy adhesives in which rubber is added to strengthen toughness, the coupling pressure is much dependent on the environmental temperature.In this study, the tensile load capability of co-cured joints composed of carbon fiber epoxy composite and steel adherends was experimentally investigated with respect to the stacking sequence of the composite and the environmental temperature. Also, the stress distributions in the composite were calculated by finite element method, from which the failure index of the composite adherend was calculated considering thermal degradation of the composite.The co-cured...
16 citations
TL;DR: In this paper, the temperature at the cutting point was measured during the cut-off grinding of carbon fiber epoxy composites, and the surface roughness under both dry and wet grinding conditions were also measured with respect to grinding speed and in-feed rate to investigate the optimum cutoff grinding characteristics of the composites.
Abstract: Although near net-shape molding of advanced composites is desirable, machining operations such as cutting, drilling and grinding on the advanced composite materials are frequently required for the composite structures to be employed for precision machine elements. During the composite machining operations, the temperature at the cutting point may increase beyond the allowed limit due to the low thermal conductivity of composites, which might degrade the properties of the composite. Therefore, in this work, the temperature at the cutting point was measured during the cut-off grinding of carbon fiber epoxy composites. The grinding force and surface roughness under both dry and wet grinding conditions were also measured with respect to grinding speed and in-feed rate to investigate the optimum cut-off grinding characteristics of the composites.
11 citations
TL;DR: In this article, the squirrel cage rotor for a high speed built-in type motor spindle system was designed and manufactured with powder containing epoxy composite material and an aluminum squirrel cage, and the Young's modulus, coefficient of thermal expansion (CTE), resistivity and magnetic permeability of the epoxy containing ferrite powder and iron powder were measured with respect to powder volume fraction.
10 citations
TL;DR: In this article, a composite pressing roller for continuous thin polymer film processing and paper manufacturing was designed and manufactured with high modulus carbon fiber composite material to exploit the high specific stiffness of composite material.
Abstract: A composite pressing roller for continuous thin polymer film processing and paper manufacturing was designed and manufactured. During thin polymer film processing, films are vulnerable to damage due to the inertia of pressing rollers especially during the start and stop periods. Therefore, pressing rollers must have low rotational inertia and high bending stiffness for uniform film thickness. In this work, the pressing roller was designed and manufactured with high modulus carbon fiber composite material to exploit the high specific stiffness of composite material. The optimal stacking sequence of the composite pressing roller and the thickness of the rubber coating layer on the composite pressing roller were calculated using FEM analysis to give uniform pressure along the axial length of the pressing roller. Then the performance of the manufactured composite pressing roller was experimentally evaluated.
4 citations
Patent•
15 Dec 2000
TL;DR: In this article, a composite material ball screw is provided to improve damping efficiency by inserting a material shaft member into the center of the screw and to stably drive at a high speed by increasing natural frequency.
Abstract: PURPOSE: A composite material ball screw is provided to improve a damping efficiency by inserting a composite material shaft member into the center of the screw and to stably drive at a high speed by increasing natural frequency. CONSTITUTION: A composite material ball screw includes a hollow shaft(11) having a screw thread(15) on an outer circumference and a composite material shaft member(12) fixed in the center along an axial direction to have a space for forming sliding friction with an inner surface of the hollow shaft through the vibration. Since the composite material shaft member is fixed only at both ends of the hollow shaft, vibration energy is vanished to friction energy due to sliding friction between the inner surface of the hollow shaft and the outer surface of the composite material shaft member to make the attenuation action become large.