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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
The Korean Society for Composite Materials
Editor in Chief :
Volume & Issues
Volume 12, Issue 6 - Dec 1999
Volume 12, Issue 5 - Oct 1999
Volume 12, Issue 4 - Aug 1999
Volume 12, Issue 3 - Jun 1999
Volume 12, Issue 2 - Apr 1999
Volume 12, Issue 1 - Feb 1999
Selecting the target year
Improvement of the Prediction of Natural Frequencies Of Composite Laminated Plate Using Parametric Identification
Composites Research, volume 12, issue 1, 1999, Pages 1~10
In order to predict the dynamic behavior of composite laminated plate accurately, the parametric identification is performed using its mechanical properties-
as design parameters. After natural frequencies are measured through simple vibration test, the objective function consists of the sum of errors between experimental and numerical frequencies of a structure. As optimization algorithm, conjugate gradient method is used to minimize the objective function. Sensitivity Analysis is performed to update design parameters during this process and can explain the result of parametric identification. In order to check the propriety of result, mode shapes are compared before and after identification. The improved prediction of natural frequencies of composite laminated plate is obtained with updated properties. For the application of result, updated properties is applied to the composite laminated plate that has different stacking sequence.
3-D Flow Analysis for Compression Molding of Fiber-Reinforced Polymeric Composites with Ratio of Extensional & Shear Viscosity
Composites Research, volume 12, issue 1, 1999, Pages 11~18
The compression molding is widely used in the automotive industry to produce products that are large, thin, lightweight and stiff. The molded product is formed by squeezing a fiber-reinforced plastic composites. During a molding process of fiber reinforced thermoplastic composites, control of filling patterns in mold, orientation and distribution of fibers are needed to predict the effects of molding parameters on the flow characteristics. It is the objective of this paper to develop an isothermal compression molding simulation that can handle both thin and thick charges and motion of the flow front, and can predict pressure distributions and accurate velocity gradients. The composites are treated as an incompressible Newtonian fluid. The effects of slip parameter
and extensional/shear viscosity ratio
on the mold filling parameters are also discussed.
Mechanical Characteristics of Carbon/Epoxy Composite for Aircraft Control System
Composites Research, volume 12, issue 1, 1999, Pages 19~27
A design development test for carbon/epoxy composite laminates for an aircraft flight control system is performed. The design development test includes moisture absorbing test, tensile, compressive, bearing and lap shear tests. The moisture absorbing behavior for different fiber orientation angles is investigated and the changes in mechanical characteristics are compared. In the in-plane tensile test, the effect of damages such as scratches and impacts is studied. The bearing test is performed for different fastening types. The resulting design allowable stress and environmental load enhancement factor are used for the structural analysis and certification tests for the flight control system.
Thermal Stress-induced Edge Failure of Thin Composite Laminates
Composites Research, volume 12, issue 1, 1999, Pages 28~36
Thermal stress-induced failure in the free edge region of various thin carbon/epoxy composite laminates(1mm thick) has been investigated using the three-dimensional finite-element stress analysis, ultrasonic C-scan and microscopic observations. High thermal in-plane and interlaminar stresses were predicted in the interior layer near the free edge boundaries of the laminates. In the interior lamina, not in the skin lamina, of the thin laminates with lay-up of
treated by liquid
immersion, many transverse matrix cracks took place due to thermal stress concentration, which agreed qualitatively with the above predictions.
A Study of Vibration Characteristics of Cylindrical Composite Shells Manufactured in Present Laboratory
Composites Research, volume 12, issue 1, 1999, Pages 37~46
In this study, the vibration analysis and modal tests of cylindrical composite shells which are manufactured with various stacking sequences in present laboratory were conducted under the free-free and clamped-clamped boundary conditions. Natural frequencies and mode shapes of these specimens were experimentally obtained and their results are compared with theoretical and FEM results. Both results are in good agreement, which confirm the usefulness of proposed manufacturing method for cylindrical composite shells.
An Experimental Study on the Free Vibration of Composite Plates with Various Shapes
Composites Research, volume 12, issue 1, 1999, Pages 47~58
This paper describes the results of experiments to analyze the free vibration of the laminated composite and hybrid composite plates with various shapes and boundary conditions. The materials of specimens were the carbon fiber reinforced plastic (CFRP), the glass fiber reinforced plastic (GFRP), the GFRP-Aluminum hybrid composite and the CFRP-CFRP hybrid composite. The natural frequencies and nodal patterns of plates with various shapes were experimentally obtained by impact exciting test using an impact hammer and an accelerometer. The experimental results were presented with normalized frequency parameters. The effects of composite material properties, fiber orientation angles, various geometrical shapes and boundary conditions on the vibration characteristics of composite plates were evaluated. To compare and verify these experimental results, the finite element analysis was carried out, and was well agreed with experimental results.
New Constitutive Models for Tensile/Compressive Nonlinear Elastic Behaviors of Composite Materials with Fiber Waviness
Composites Research, volume 12, issue 1, 1999, Pages 59~67
The effects of fiber waviness on tensile/compressive nonlinear elastic behaviors of graphite/epoxy unidirectional composite materials are studied theoretically and experimentally. New constitutive models are proposed to predict elastic properties and tensile/compressive nonlinear behaviors of composite materials. Three types of wavy pattern are considered: uniform, graded and localized fiber waviness. Complementary energy density and incremental method are used to incorporate the material and geometrical nonlinearities due to fiber waviness. Tensile/compressive tests are conducted on the specimens with fiber waviness. It is found that the predictions are in good agreement with the experimental results.
Dynamic Behaviors of Metal Matrix Composites in Low Velocity Impact
;Gamal A. Aggag;K.Takahashi;;
Composites Research, volume 12, issue 1, 1999, Pages 68~75
This study has observed that the dynamic behavior of Metal Matrix Composites (MMCs) in low velocity impact varies with impact velocity. MMCs with 15 fiber volume percent were fabricated by using the squeeze casting method. The AC8A was used as the matrix, and the alumina and the carbon were used as reinforcements. The tensile and vibration tests conducted yielded the yielded the tensile stress and elastic modulus of MMCs The low pass filter and instrumented impact test machine was adopted to study dynamic behaviors of MMCs corresponding to impact velocity. Stable impact signals were obtained by using the low pass filter. Impact corresponding to impact velocity. Stable impact signals were obtained by using the low pass filter. Impact energy of unreinforced alloy and MM s increased as the impact velocity increased. The increase of crack propagation energy was especially prominent, but the dynamic toughness of each material did not change much. To show the relation between crack initiation energy and dynamic fracture toughness, a simple model was proposed by using the strain energy and stress distribution at notch. The model revealed that crack initiation energy is proportional to the square of dynamic fracture toughness and inversely proportional to elastic modulus.