Papers by Author: Jin Ho Choi

Abstract: Rapid prototyping (RP) can efficiently fabricate high level models with complex shapes. Hence the RP has been widely applied in various industrial fields. However, as the technology is inherently performed by layered manufacturing process, the surface quality of the RP part is not satisfactory to use general industrial purpose. This is the reason that surface roughness problem has been key issue in RP. In this paper, relation between surface roughness and overlap interval is investigated based on a surface roughness formulation in fused deposition modeling (FDM). Additionally, effects of surface angle and filament shape are analyzed and discussed to predict surface roughness distribution by the overlap interval variation.

Abstract: Aeroelastic tailoring studies using effective computational method with genetic algorithm have been conducted to find an optimized lamination set which give minimum structural weight. The efficient and robust computational system for the flutter optimization has been developed using the coupled computational method based on the micro genetic algorithm. It is shown that the wing structural weight with both divergence and flutter constrains can be significantly reduced using composite materials with proper optimum lamination compared to the case of isotropic wing model.

Abstract: A two-dimensional progressive failure analysis is conducted to predict the failure loads and modes of carbon-epoxy composite joints under pin-loading. An eight-node laminated shell element is used for the finite element modeling. Post-failure stiffness is evaluated based on the complete unloading model combined with various failure criteria. The comparison of finite element and experimental results shows that the finite element analysis based on the combined maximum stress and Yamada-Sun criteria most accurately predicts the failure loads of the composite laminated joints.

Abstract: As these composites have become more popular, composite joint design has become a very important research area, as these joints are often the weakest parts of composite structures. In this paper, the strength of a composite laminated bolted joint being subjected to a clamping force was tested and predicted using the FAI (Failure Area Index) method. The strengths of composite joints subjected to clamping forces on different geometric shapes and dimensions were predicted using the FAI method, and the results were compared with experimental results. From the tests and analyses, the strength of a given composite laminated bolted joint subjected to a clamping force could be predicted within 22.5% via the FAI method.

Abstract: Progressive failure analysis based on the complete unloading method was conducted to investigate the crippling failure of carbon/epoxy composite stiffeners under axial compression. A modified arc-length algorithm was incorporated into a nonlinear finite element method to trace the equilibrium path after local buckling. For the validation of the finite element method, several carbon/epoxy Z-section stiffeners were tested in compression. The finite element results on the buckling and crippling stresses showed good agreement with the experimental results.