• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.8-17
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• 2022

This paper presents a novel geometric modeling technique to predict the mechanical properties of an aircraft wing's skin-stringer integrated panel. Due to mechanical and adhesive fastening, this panel is vulnerable to stress concentration and debonding, so we designed it to integrate the skin and stringer using three-dimensional woven composites. Geometric modeling was conducted by measuring the geometric parameters of the specimen and defining the pattern of the yarns as functions. We used a weighted average model with iso-strain and iso-stress assumptions to predict the mechanical properties of the panel parts. We then compared the results of a finite element analysis with a compression test to verify the accuracy of our model. Our proposed technique proved to be more efficient than the traditional experimental method for predicting the mechanical properties of skin-stringer integrated panels.

• Composites Research
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• v.27 no.4
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• pp.158-167
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• 2014

Final goal of this research is to establish the database for correlation factors which connects the test and analysis results of shear buckling allowables for composite plate. To accomplish the goal, extensive test and analysis works are required. In this paper, as the first step, a frame-type fixture for shear buckling test was designed and validated through the test and analysis. Final configuration of the fixture were determined via parametric study on the effect of specimen size, cross-sectional dimensions, and number of fastening bolts on the shear buckling load. Results of the study showed the designed frame-type fixture successfully induces the shear buckling of composite plate. However, there were deviations between the test results and analysis results for ideal case under pure shear load, which were mainly caused by the difference in plate sizes for both cases. The difference were larger in the plates with larger hole and simply supported boundary condition. It is concluded from the results that while the designed fixture can be used for the clamped plates with acceptable accuracy, it shows larger difference in the simply supported plates.

• Composites Research
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• v.18 no.6
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• pp.9-18
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• 2005

With the wide applications of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joints have become a very important research area because the joints are often the weakest areas in composite structures. This paper presents an analytical study of the stress distributions in mechanically single-fastened and multi-fastened composite laminates. The finite element models which treat the pin and hole contact problem using a contact stress analysis are described. A dimensionless stress concentration factor is used to compare the stress distributions in composite laminates quantitatively In the case of single-pin loaded composite laminate, the effects of stacking sequence, the ratio of a hole diameter and the width of a laminate (W/D ratio), the ratio of hole diameter and distance from edge to hole (E/D ratio), friction coefficient and clamping force are considered. In the case of multi-pin loaded composite laminate, the influence of the number of pins, pitch distance, number of rows, row spacing and hole pattern are considered. The results show that P/D ratio and E/D ratio affect more on stress distributions near the hole boundary than the other factors. In the case of multi-pin loaded composite laminate, the stress concentration in the double column case is better than the other cases of multi-pin loaded composite laminate.

• Composites Research
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• v.31 no.4
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• pp.139-144
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• 2018

Long Fiber-reinforced composites have advantages of excellent production efficiency and formability of complex shapes compared to conventional continuous fiber reinforced composite materials. However, if we need to make complicated composite shapes or to assemble parts made of different materials, a variety of joining methods are needed. In general, long fiber prepreg sheet (LFPS) contains mold release agent to facilitate demolding after thermoforming. Therefore, mechanical fastening is required in addition to the adhesive bonding to get proper joining strength. In this study, we proposed a stainless steel insert for co-cure bonding which cures LFPS and bonds the stainless steel insert through thermoforming process. The wing of the insert which is spread during the thermoforming process induces adhesion and mechanical wedging effect and serves as a hook to resist the pulling force. The burn-out method was used to confirm the unfolded state of the stainless steel insert wings inserted into the composite material. The static pull-out test was performed to quantitatively evaluate the joining strength. From these experimental results, the condition which guarantees the most appropriate joining strength was derived.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.8
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• pp.378-385
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• 2017

This study investigated the design of a snap fit, which is widely used for fastening plastic parts. We analyzed the assembly mechanism of a lock snapfit, measured the assembly force and separation force based on the design of experiments, and derived a regression equation through an analysis of variance. The response surface methodology was also used. Polybutylene terephthalate was used to fabricate specimens, and the assembly force and separation force were measured using a micro-tensile tester. The length, width, thickness, and interference were considered as factors. A second-order regression model was used to derive the regression equation. The assembly force decreased with increasing length and width, but it increased with increasing thickness and interference. The finite element method was used to analyze the assembly mechanics. The width decreased the assembly force by increasing the ductility. The influences of the factors for low assembly force and high release force were shown to be opposite to each other. It was necessary to design a structure that minimized the assembly force while maintaining an appropriate level of separation force.