• Composites Research
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• v.30 no.4
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• pp.241-246
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• 2017

The brittle nature in most FRP composites is accompanying other forms of energy absorption mechanisms such as fibre-matrix interface debonding and ply delamination. It could play an important role on the energy absorption capability of composite structures. To solve the brittle nature, the adhesion between pines and composites was studied. Thermal treated pines were attached on carbon fiber reinforced polymer (CFRP) by epoxy adhesives. To find the optimum condition of thermal treatment for pine, two different thermal treatments at 160 and $200^{\circ}C$ were compared to the neat case. To evaluate mechanical and interfacial properties of pines and pine/CFRP composites, tensile, lap shear and Izod test were carried out. The bonding force of pine grains was measured by tensile test at transverse direction and the elastic wave from fracture of pines was analyzed. The mechanical, interfacial properties and bonding force at $160^{\circ}C$ treated pine were highest due to the reinforced effect of pine. However, excessive thermal treatment resulted in the degradation of hemicellulose and leads to the deterioration in mechanical and interfacial properties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.832-842
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• 1996

Fatigue life prediction and fatigue behavior of circular notched carbon fiber reinforced plastic laminates are presented. Point and average stress criteria by Whitney and Nuismer are generalized to fatigue fracture criteria for notched laminates. Residual strength degradation model and the assumptions on the stress redistribution are introduced during the derivation of prediction equations. S-N curve, Basquin's relation, and H and H's FLPE1 are chosen for evaluation of residual strength of unnotched laminates and six prediction equations are derived. Experiments are performed using Graphite/Epoxy laminates whose fiber orientation is $[0$^\circ$/+45$^\circ$/-45$^\circ$/90$^\circ$]s. Presented prediction equations are reasonably close to experimental data and proposed appoach is found to be suitable to predict fatigue life of notched composite laminates.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.6
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• pp.439-445
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• 2016

Carbon fiber reinforced plastic (CFRP) composites have been widely used due to their great strength, stiffness and light weight. However, due to its anisotropy and inhomogeneous properties the machining process of CFRP composites is typically more complex than that of regular metals. Since there are many defects, such as delamination and tool wear during the machining process of CFRP composites, the optimization of this process is essential in improving the productivity. In this study, orthogonal machining of CFRP composites was performed to identify the machining characteristics of these materials. In addition, an experimental observation of delamination was investigated through the use of scanning electron microscopy (SEM). In these experiments, the cutting forces were measured and analyzed to determine the difference between machining of CFRP composites and metals. The comparison between the numerical models and experimental results was performed in terms of the maximum cutting forces.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.2
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• pp.1-7
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• 2013

In recent years, fiber reinforced polymer plastic composites are readily available in the construction industry. Fiber reinforced polymer composite has many advantages such as high specific strength and high specific stiffness, high corrosion resistance, light-weight, magnetic transparency, etc. In this paper, we present the result of investigation pertaining to the flexural behavior of flange strengthened I-shape pultruded fiber reinforced polymer plastic (PFRP) member using carbon fiber sheet (CFRP sheet). Test variable is consisted of the number of layers of strengthening CFRP sheet from 0 to 3. From the experimental results, flexural strengthening effect of flange strengthened I-shape PFRP member using CFRP sheet is evaluated and it was found that 2 layers of strengthening CFRP sheet are appropriate considering efficiency and workability.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.149-157
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• 2002

This paper is to investigate collapse mechanisms of CFRP(Carbon Fiber Reinforced Plastics)composite tubes and to evaluate collapse characteristics on the change of interlaiminar number and ply orientation angle of outer under static and impact axial compression loads. When a CFRP composite tube is crushed, static/impact energy is consumed by friction between the loading plate and the splayed fronds of the tube, by fracture of the fibers, matrix and their interface. These are associated with the energy absorption capability. In general, CFRP tube with 6 interlaminar number(C-type), absorbed more energy than other tubes(A, B, D-types). The maximum collapse load seemed to increase as the interlaminar number of such tubes increases. The collapse mode depended upon orientation angle of outer of CFRP tubes and loading status(static/impact). Typical collapse modes of CFRP tubes are wedge collapse mode, splaying collapse mode and fragmentation collapse mode. The wedge collapse mode was shown in case of CFRP tubes with 0° orientation angle of outer under static and impact loadings. The splaying collapse mode was shown in only case of CFRP tubes with 90°orientation angle of outer under static loadings, however in Impact tests those were collapsed in fragmentation mode .

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1341-1344
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• 2003

Studies on impact damage of composite laminate shells were fewer compared with those on impact behaviors to analyze time-load, displacement-load and impact energy - energy absorption. Up to date the studies were not enough to demonstrate suitability of their results because they were dependent on theories and numerical analyses. In particular, it is a well-known fact that there was a correlation between initial peak load and damage resistance of composite material flat plates imposed with low-speed impact, but studies on composite material shells with curvature were also very few. Actually structures such as wings or moving bodies of airplanes, motor cases and pressure containers of rockets are circular. And as low-speed impact load is imposed for optimal design of take-off and landing, and containers of airplanes, it is very important to analyze evaluation of behaviors and damaged areas. Therefore, in this paper to evaluate the impact characteristics of the CFRP laminate shell according to size of curvature quantitatively, it was to identify energy absorption and impact damage instruments according to change of impact speed.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.65-72
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• 2013

This paper describes a finite element analysis (FEA) of the body frame of a subsea robot, Crabster200 (CR200). CR200 has six legs for mobility instead of screw type propellers, which distinguishes it from previous underwater robots such as remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs). Another distinguishing characteristic is the body frame, which is made of carbon fiber reinforced plastic (CFRP). This body frame is designed as a rib cage structure in order to disperse the applied external loads and reduce the weight. The frame should be strong enough to support many devices for exploration and operation underwater. For a reasonable FEA, we carried out specimen tests. Using the obtained material properties, we performed a modal analysis and FEA for CR200 with a ready posture. Finally, this paper presents the FEA results for the CFRP body frame and the compares the characteristics of CFRP with conventional material, aluminum.

• Journal of Aerospace System Engineering
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• v.12 no.6
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• pp.58-65
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• 2018

The dynamic characteristics of the deployable composite parabolic reflector with several panels were numerically and experimentally investigated. The deployment mechanism is designed to efficiently fit in a small volume. The parameters guiding the deployment are determined by considering; the number of panels, folding/twisting angles, and the driving forces of actuating devices. The panels are fabricated using carbon fiber reinforced plastics (CFRPs). The zero-gravity simulator is manufactured for the unfolding test. The deployment behaviors of the reflector are finally observed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.649-654
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• 2002

In recent days the more use of CFRP composite is in the airplane, automobile, and sport goods , etc., the more necessity of research on it in this engineering. In this research, the CFRP composite specimen are fabricated by 48 CFRP plies with 8 orientation angles, and the specimens are drilled with 3 tools. The results are analyzed with consideration of cutting force, type of tools and fabrication condition. The specimens with each drilling conditions are also investigated with SEM. The optimal drilling conditions such as drill types and cutting fence with respect to the fabricating condition are studied.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.3
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• pp.241-247
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• 2009

It is important to satisfy the requirements and standards for the protections of passengers in a car accident. There are lots of studies on the crushing energy absorption of a structure members in automobiles. We have studied to investigate collapse characteristics and moisture absorption movements of CFRP(Carbon Fiber Reinforced Plastics) hat shaped sectional members when CFRP laminates are under the hygrothermal environment. In particular, the absorbed energy, mean collapse load and deformation mode were analyzed for side members which absorbed most of the collision energy. Variation of CFRP interlaminar numbers is important to increase the energy absorption capability. Therefore we have made a static collapse experiment to research into the difference of absorbed energy and deformation mode between moisture absorbed specimen and non-moisture absorbed.