Composite materials have the strong durability and light weight as inhomogeneous material. These material are manufactured by combining and maximizing the advantage of each material. Among these various materials, stainless steel, aluminum and brass has been used generally. Prior to using, the preparatory experiments are demanded in order to obtain the material strengths. In this study, the tensile tests are carried out with the specimens of stainless steel, aluminum and brass. These tensile specimens of same standards are made with the notches at both sides of specimen. When the forced displacement of about 11 mm proceeds in case of stainless steel specimen, the maximum load of 31000 N is shown simultaneously with the fracture of specimen. When the forced displacement of about 6 mm proceeds in case of aluminum specimen, the maximum load of 20600 N is shown simultaneously with the fracture of specimen. When the forced displacement of about 7 mm proceeds in case of brass specimen, the maximum load of 25000 N is shown. In this study, the finite element analysis as ANSYS program is carried out in order to verify these experimental results. The experimental and analysis results are similarly shown each other. Through the result of this study, the analysis data with no experiments are thought to be trustworthy as the tensile experimental data.

In order to provide the basis data for broad use and safe design of carbon fiber reinforced plastic, this paper aims at investigating the fracture behavior on CFRP specimen composed of one directional fiber through three point bending test. On the basis of experimental result, the improvement of composite layer specimen can be secured with the other data to compare the existing specimen. The fracture behavior happened at the experimental procedure is investigated in this study. The maximum loads of 1200 N, 1700N and 1600N are shown respectively at the specimens with the layer angles of 30°, 45° and 60°. The highest load is shown at the layer angle of 60° among all specimens and the longest displacement is maintained until each of the layer structure is broken down. The fracture due to the force applied from the outside can be prevented by applying the result of this study to the real structure. As structural safety can be evaluated and anticipated through this study, it is thought that the safe design is devoted.

In this study, the buckling restoration at CFRP 3-Point bending specimen composed of 30°, 45°and 60° is investigated when the pressure at the lowest position on the compressed specimen is eliminated. The fracture configuration and stress contour of the specimen can be seen according to the laminate angle of fiber. The result of this study is thought to apply the data for the safe design of CFRP structure.

CFRP hardened by carbon fiber and resin has the property of high strength and low weight. Specifically, the strong feature against the external vibration environment is shown as CFRP is designed with the structure of multi-axes. So, CFRP in place of metal has been used at the various fields. CFRP specimens for mode Ⅱ are applied with the repetitive fatigue load in this study. These specimens have the fiber layer angles of 30°, 45° and 60°. The material properties of specimens are investigated with the result of fatigue fracture due to this load. As the study result, the smallest and largest reaction forces of 500 N and 540 N are shown at the layer angle of 30° and 60° respectively among these specimens. The separation of adhesive interface at 4000 fatigue cycles is happened earliest in case of the layer angle of 60°. But the separation of adhesive interface at 11000 fatigue cycles is happened latest in case of the layer angle of 45°. Through the result of fatigue property, it is thought that the basis data can be applied to evaluate the safety at CFRP structure applied with fatigue.

As CFRP as the single material has various material properties, it has been used at many fields. CFRP is utilized at the mechanical structure on the basis of the brittle fracture property and the performance of vibration damping. CFRP composed of multiple axes has the high natural frequency. It is shown to have more reinforced material property with the fiber design. This paper investigates the fatigue property of the bonded specimen for mode 1 at the laminate angles of 30°, 45° and 60°. According to the fiber design, each specimen bonded with the laminate angle is shown to have different fatigue property repectively. As the laminate angle is increased, the reaction force tends to be increased. In this paper, the laminate angle through the fiber design of CFRP is applied and the fatigue property at mode 1 is investigated. Through the study result, The safety of fatigue fracture is also checked at applying to the composite structure.

This study aims at analyzing the property of the structural body bonded with alumimum foam by the utilization of the aluminum foam of closed type used generally with impact absorbent. The structural bodies bonded with the aluminum foam of DCB and TDCB are designed in this study, and then the fatigue analysis and experiment are carried out. At fatigue analysis, the maximum load happens at all of each specimen models when the fatigue life of 0 to 50 cycle is proceeded. And from the point of time that the maximum load happens, the load at the bonded surface is seen to be decreased in cases of analysis and experiment. As the specimen thickness is increased, the maximum load happened at specimen is increased. It is confirmed that the result of fatigue analysis becomes similar to that of fatigue experiment for verification. It is thought that the study data on various specimen thicknesses can be secured simply without the extra fatigue experimental procedure. By using this study result, the mechanical properties of the structural bodies bonded with the alumimum foams of DCB and TDCB with mode Ⅲ type can be thought to be analyzed effectively.

Because aluminum foam is porous material, the frature property is different from that of non-porous material. This aluminum foam can be used with the joint bonded with adhesive in order to utilize the light weight to the maximum. So, the study of fracture property on bonded surface can be important. In this study, the analyses on the specimens with two kinds of configuration as DCB(Double Cantilever Beams) and TDCB(Tapered Double Cantilever Beams) aluminum foams of mode Ⅲ type bonded with adhesive are carried out and compared with each other. And the fracture properties the adhesive surfaces of the structure with bonded aluminum foams are studied as the static experiments on these verifications are done. DCB and TDCB specimens used in this study have the variable of thickness(t) as 35mm, 45mm and 55mm. As the result of this study, the range of reaction forces are 0.3 to 0.8 kN and 0.5 to 1.2 kN at DCB and TDCB specimens respectively. The results of the static experiments can also be confirmed with these similar results. These study results can be obtained by only a simulation without the special experimental procedures. The mechanical properties of the bonded structures composed of DCB and TDCB aluminum foams with mode Ⅲ type can be thought to be analyzed effectively.

Nowadays, the study of CFRP reinforced with carbon fiber is focused on improving the the mechanical property. The study on the fracture data of CFRP are not properly made out than that of the general mechanical joint. In this study, the fracture property of mode 1 at the same condition of tensile experiment is investigated by applying the layer angle to laminated CFRP with the thickness of 15 mm. When the reaction forces until dropping out the bonded surface are compared with the cases of the layer angles of 0°, 45° and 60°, the reaction force is shown to be most and the elapsed time until dropping out the bonded surface is longest at that of 45°. The deformation energy is also shown to have the highest value by dropping out the adhesive interface. As the basis of the analysis result of this study, the most safety with fracture resistance is shown in the case of 45°. the bonded structure applying the appropriate layer angle is thought to have the structural safety.

CFRP has the high strength and low weight. But it tends to be frail if it is applied with the mechanical bonding method using weld, rivet or bolt. So, the chemical bonding method using the special adhesive has been utilized. By applying the bonding method with the adhesive, this paper investigates the mechanical property of DCB specimen bonded with the type of mode 2 through the simulation analysis. Four kinds of specimen thicknesses are 25mm, 35mm, 45mm and 55mm in this study. The mechanical behaviors of specimens due to the forced displacements are investigated as the distributions of equivalent stresses. The reaction force becomes higher as the specimen thickness is increased. The result of this study about the fracture property of adhesive joint is thought to be contributed to the safe design of structure with CFRP.

As aluminum foam has the most superior absorption of impact energy, this material has been used at automobile and airplane. If aluminum foam is used by jointing bolt and nut, it can be broken. Therefore, it is more effective to bond aluminum foam and other materials by adhesive. In this study, the fatigue fracture simulation through ANSYS program is carried out on the aluminum foam specimen bonded with adhesive as the type of DCB Mode Ⅲ. There are four kinds of specimens with the types of DCB Mode Ⅲ in this study. The thicknesses of four specimens are 35mm, 45mm, 55mm and 65mm. In cases of specimen thicknesses of 35mm, 45mm, 55mm and 65mm, the maximum loads are shown as ±0.2kN, ±0.55kN, ±1kN and ±1.2kN respectively. As the specimen thickness increases, the maximum loads increase. The results of fatigue experiment as specimen thickness of 55mm can be shown to approach the simulation results by confirming the simulation results of this study. So, The simulation data can be applied in order to investigate the mechanical property at DCB specimen with the type of Mode Ⅲ.

This study investigates the property of crack growth at the specimen of structural steel. The behaviour of fracture mechanics on the specimens with only a center crack and with holes existed symmetrically near a center crack is studied. The tensile load is applied on the specimens with these conditions. Stress intensity factors are obtained by the basis of these experimental values and these values are verified with the structural analysis of finite element method. As the length of center crack becomes larger in case of the specimen with holes existed symmetrically near a center crack, the values of deformation energy and stress become larger. On the contrary, the values of deformation energy and stress become smaller as the length of center crack becomes larger in case of the specimen with only a center crack. By examining the stress intensity factor in this study, this value becomes rather smaller although the length of center crack becomes larger. There is the position where crack is likely to happen or weak part at the mechanical structure or the machine. As the holes are punctured and arranged adequately near this crack or weak part by using the result of this study, the fracture due to it can be prevented.

본 연구에서는 구조용강 시험편 내의 크랙의 성장특성을 주제로 하여 중앙크랙만이 존재하는 시험편과 중앙 크랙의 주변에 대칭으로 구멍들이 존재하는 시험편에 대한 파괴역학적 거동을 규명하고자 하였다. 구조용강으로 만들어진 시험편 내에 두 가지의 조건들을 적용하여 인장실험을 수행하였으며, 이를 통하여 시험편의 응력, Strain energy와 변형량에 대하여 해석하였다. 그리고 이러한 실험값들을 바탕으로 하여 응력확대계수를 구하였으며, 구해진 실험값들의 검증을 위하여 ANSYS 유한요소 해석 프로그램을 사용하여 시뮬레이션 해석을 수행하였다.

The Notched Ring Test(NRT) has proven to be very useful in determining the slow crack growth behavior of polyethylene pressure pipes. In particular, the test is simple and an order of magnitude shorter in experimental times as compared to the currently used Notched Pipe Test(NPT), which makes this method attractive for use as the accelerated slow crack growth test. In addition, since the NRT specimen is taken directly from the pipe, having maintained the cross-section, processing induced artifacts that would affect the slow crack growth behavior are not altered. This makes the direct comparison to the slow crack growth specimen in pipe from more meaningful. In this study, for comparison with other available slow crack growth methods, including the NPT, the stress intensity factor equation for NRT specimen was developed and demonstrated of its accuracy within 3% of that obtained from the finite element analysis. The equation was derived using a flexure formula of curved beam bending along with numerically determined geometric factors. The accuracy of the equation was successfully tested on 63, 110, 140, 160, 250, and 400 mm nominal pipe diameters, with crack depth ranging from 15 % to 45 % of the pipe wall thickness, and for standard dimensional ratio(SDR) of 9, 11, and 13.6. Using this equation the slow crack results from 110SDR11 NRT specimen were compared to that from the NPT specimen, which demonstrated that the NRT specimen was equivalent to the NPT specimen in creating the slow crack, however in much shorter experimental times.

이중외팔보 모델은 일반적으로 복합재료의 구조테스트와 접착 접합의 테스트에 많이 쓰인다. 본 연구 에서 쓰인 재료는 알루미늄 합금2014이다. 또한 접착 구조물의 접착 면에서 발생한 에너지 해방율 및 유한요소해석을 통하여 알루미늄의 충격에 대한 기계적 특성을 알고자 하는 것이 목적에 있다. 상단부와 하단부의 접착 부위는 하중 점으로부터 100mm 떨어지도록 예비크랙을 두어 접착을 하도록 설계하였다. 하중은 핀에 Y축 방향으로 작용하였다. 충격속도는 7. 5m/s와 12.5m/s로 가하였다. 충격속도가 12.5m/s 일 때의 에너지 해방율은 약 7500J/m2으로 나왔다. 충격 속도가 빠를수록 하중 핀에 가해지는 하중이 증가된다는 것을 알 수 있었으며, 에너지 해방율도 높게 나타나는 것을 알 수 있었다.

본 연구는 알루미늄 폼 복합재료로 접합된 TDCB 모델에 대해 구조적 시뮬레이션 해석을 하였다. 이 해석을 통하여 등가응력, 변형 에너지 및 접착부의 압력에 대한 자료를 얻었다. 또한 실험을 하여 해석 자료에 대한 검증을 하였다. 본 연구의 자료를 통해 알루미늄 폼 재질로 접합된 실제 복합재 구조물에 적용시켜 파괴거동을 분석하고 그 기계적인 특성을 파악할 수 있다.

Aluminum foam as porous material in wide use has the excellent mechanical and thermal properties. As adhesive process technique is used by bonding such composites as aluminum foam, fracture toughness at adhesive joint is the main point to investigate. In this study, DCB specimens are manufactured to evaluate the strengths at adhesive joints on the basis of British industrial and ISO international standards. Four kinds of specimens are made by changing the height of the specimen and these experimental results are compared with each other. Energy release rates are also calculated at mode I. As the hight of specimen becomes higher, reaction force and energy release rates become higher. Through the correlation obtained by this study result, aluminum foam material bonded with adhesive can be applied to the real composite structure and mechanical property and fracture toughness are analyzed systematically.