• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2001.11a
• /
• pp.136-141
• /
• 2001

If we build new building after demolition of commercial building that is located in the downtown, it will be caused a social and environmental problem as wasting of resources and generating of waste. In this study, I investigated about remodel ins, this conclusion is given below. 1. Reconstruction cost is 2.1 times, and construction period is 1.4 times as much remodeling. So remodeling has an advantage. 2. For repairing and reinforcing timeworn building, we reinforced it as using carbon fiber sheet (girder, slab) and injecting method steel plate bonding Also, we tried to maintain efficiency of new building as using epoxy to protect concrete crack. 3. In the side of waste products and cost, remodeling has much more advantage than reconstruct. But demolition used construction period much. Because it had to be reused as repairing and reinforcing. And there was no difference between remodeling cost and reconstruct cost. If we develop research with enterprise.university.laboratory to exploit material and equipment and to train specialized engineer who will has a capacity to know construct repair and reinforce, it can be attribute to prevail remodeling in new construct market.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.675-678
• /
• 2001

In this paper, an investigation was performed on the dynamic interlaminar fracture toughness of CFRP(carbon fiber reinforcement plastics). Specimens used in this experiment are CF/EPOXY laminated plates. In this experiments, Split Hopkinson s Bar test was applied to dynamic and notched flexure test. The mode II fracture toughness of each unidirectional CFRP was estimated by the analyzed deflection of the specimen and J-integral with the measured impulsive load and reactions at the supported points. As an experimental result, the vibration amplitude of 〔$0_{10}F_4/0_{10}$〕laminates appear more than that of 〔0_{10}/F_2/0_{10}$〕laminates for the J-integral and displacement velocity at a measuring point. Also, it is thought that the dynamic fracture toughness of two kind specimen with the increase of displacement velocity becomes great at a measuring point with in range of measurement.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.773-776
• /
• 1997

This paper presents an investigation of the energy absorption of composite laminates during ballistic impact. Three components are responsible for the absorption of energy-the tensile failure of fiber, the elastic deformation of the composite, the delamination of composite laminates. The ballistic limit, V/sub 0/, of the laminates is determined using a previous model implemented to determine the energy absorption of the three components listed above. The size of the deformed zone during impact was estimated by an approximate solution for impacts on plates. The carbon/epoxy plates were examined for this research.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.591-596
• /
• 2003

Many studies have dealt with strengthening by epoxy-bonded CFRP(Carbon Fiber Reinforced Polymer) composites. However, the effects of various influencing factors have not been clarified on the behavior of strengthened RC beams. This study was performed to verify the effects of strengthening due to various bond details of externally attached CFRP Composites. In this study, major test parameters include the bond type and the anchor type. The deflections, failure load, strain of reinforcing bar, concrete and CFRP are measured at each loading step. The failure mode and debonding loads(ultimate loads) are analysed from these measured data. According to the test results, all specimens are failed by intermediate flexural crack induced interfacial debonding.

• Journal of Ocean Engineering and Technology
• /
• v.11 no.4
• /
• pp.23-30
• /
• 1997

The purpose of this paper is to investigate the water environmental effect on the mechanical properties of carbon fiber/epoxy composites. Moisture concentration absorbed in CFRP under various water environment was calculated and degradation of mechanical properties for each wet composite laminates is investigated by performing the flexual and tensile test. The results show that moisture absorption is accelerated in higher temperature environment and under the same temperature sea water environment prompts more absorption than fresh water. As increasing the water temperature and moisture concentration tensile and flexual strength decreased as much as 25%-40% compared with dry condition.

• Composites Research
• /
• v.13 no.5
• /
• pp.44-49
• /
• 2000

Although the net-shape molding of composites is generally recommended, molded composites frequently requires cutting or grinding due to the dimensional inaccuracy for precision machine elements. The surface roughness and cutting force were also measured to investigate the surface grinding characteristics of the composites using the vitrified bonded wheel (WA, GC). The experiments were performed dry grinding conditions with respect to cutting speed, feed speed, depth of cut of the stacking sequence $[O]_{nT.}$ From the experimental investigation, the optimal conditions both the vitrified bonded wheel WA and GC for the surface grinding are suggested.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.4
• /
• pp.147-155
• /
• 1996

The purpose of present paper is to estimate the static and fatigue bending strengths of CFRP(carbon fiber reinforced plastic) laminates having impact damage(FOD). The specimens which are formed with the different stacking composition, EPOXY and PEEK matirx and orthotropic and quasi-isotropic laminated plates, are prepared for this experiment. A steel ball is impacted on CFRP laminates, generating impact damages, and the three-point fatigue bending test is carried out by using the impacted laminates to investigate the influence of the stackin composition on the fatigue strength of CFRP laminates.

• The Korean Journal of Rheology
• /
• v.6 no.1
• /
• pp.10-19
• /
• 1994

에폭시수지와 CFRP 복합체 구조물의 경화공정 중에 발생하는 잔류응력은 구조물의 기계적물성에 영향을 미친다. 따라서 잔류응력을 낮추기 위해 여러 가지 방법들이 발표되고 있다. 이연구에서는 잔류응력을 낮추는 방법으로 잔류응력의 발새mechanism을 이해하고 반 응속도식과 여러 가지 기초물성을 기초로 한 computer simulation pro-gram을 이용하여 에 촉시수지와 복합체 구조물의 잔류응력을 최소화하는 경화공정을 찾는 연구를 진행하였다. 경화과정에서는 대부분의 경화온도가 구조물의 유리전이온도보다 높기 때문에 잔류응력이 발생하지 않고 대부분의 잔류응력은 냉각과정에서 발생하였다. 잔류응력을 정량화하는 방법 으로 구조물의 표면이 유리전이온도에 도달하였을때 내부 비체적분초를 상대적인 잔류응력 이라 간주하였다. 컴퓨터모사에 의해 최종경화온도와 냉각속도를 바꾸면서 잔류응력을 모사 한 결과 최종경화온도가 낮을수록, 냉각속도가 작을수록 잔류응력이 작게 발생하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.3
• /
• pp.274-281
• /
• 2009

The carbon fiber epoxy composite material and aluminum have many advantages over other materials because of their high specific stiffness and good fatigue characteristics. Basically, the propeller shaft of automobile requires bending frequency of higher than 2,700 Nm and high natural frequency of higher than 9,200 rpm occurred by fast revolution. For this reason, natural frequency and torsion torque characteristics of hybrid shaft was studied in variation of its outer-diameter and thickness. Vibration and torque characteristics of hybrid shaft were compared by torsion tester, natural frequency experiments and FE analysis. Designed hybrid shaft satisfied its vibration and torque characteristics when its outer-diameter was 60 mm and thickness was 5 mm. Therefore, hybrid material enables to manufacture one piece structure hybrid propeller shaft rather than current two piece structure.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.6
• /
• pp.1003-1007
• /
• 2012

A nondestructive technique would be very useful. Advanced NDE T-ray (terahertz ray) techniques of technology and instrumentation has provided a probing field on the electromagnetic spectrum. However, the T-ray is limited in order to penetrate a conducting material to some degree. Here, the T-ray would not go through easily the CFRP composite laminates since carbon fibers are electrically conducting while the epoxy matrix is not. So, investigation of terahertz time domain spectroscopy (THz TDS) was made and reflection and transmission configurations were studied for a 48-ply thermoplastic PPS(poly-phenylene sulfide)-based CFRP solid laminate. It is found that the electrical conductivity of CFRP composites depends on the direction of unidirectional fibers.