• Proceedings of the Safety Management and Science Conference
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• 2001.05a
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• pp.311-317
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• 2001

The notched Charpy and Izod impact tests are the most prevalent techniques used to characterize the effects of high impulse loads on ploymeric materials. An analysis method for rubber toughened PVC is suggested to evaluate critical strain energy release rates(Gc) from the Charpy impact energy measurements. An Instrumented Charpy Impact tester was used to extract ancillary information concerning fracture properties in addition to total fracture properties and maximum critical loads. The stress intensity factor Kd was computed for varying amounts of rubber contents from the obtained maximum critical loads and also toughening effects were investigated as well.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.125-128
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• 2003

Low-velocity impact damage is a major concern in the design of structures made of composite materials, because impact damage is hidden inside and cannot be detected by visual inspection. The piezoelectric thin film sensor can be used to detect variations in structural and material properties for structural health monitoring. In this paper, the PVDF and PZT sensors were used for monitoring impact damage initiation in Gr/Ep composite panel to illustrate this potential benefit. A series of impact test at various impact energy by changing impact mass and height is performed on the instrumented drop weight impact tester. The wavelet transform(WT) is used to decompose the piezoelectric sensor signals in this study. Test results show that the particular waveform of sensor signals implying the damage initiation and development are detected above the damage initiation impact energy. And it is found that both PZT and PVDF sensors can be used to detect the impact damage.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.174-178
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• 2001

The piezoelectric thin film sensor can be used to interpret variations in structural and material properties, e.g. for structural integrity monitoring and assessment. To illustrate one of this potential benefit, PVDF film sensors are used for monitoring impact damage initiation in Gr/Ep composite panel. Both PVDF film sensors and strain gages are surface mounted to the Gr/Ep specimens. A series of impact test at various impact energy by changing impact mass and height is performed on the instrumented drop weight impact tester. The sensor responses are carefully examined to predict the onset of impact damage such as matrix cracking, delamination, and fiber breakage, etc. Test results show that the particular waveforms of sensor signals implying the damage initiation and development are detected above the damage initiation impact energy. As expected, the PVDF film sensor is found to be more sensitive to impact damage initiation event than the strain gage.

• International Journal of Automotive Technology
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• v.4 no.4
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• pp.203-211
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• 2003

This paper describes a method for a falling weight impact test to estimate the impact energy absorbing characteristics and impact strength of CFRP (Carbon-fiber reinforced plastics) laminate plates based on considerations of stress wave propagation theory, which were converted to measurements of load and displacement verses time. The delamination area of impacted specimens for the different ply orientations was measured with an ultrasonic C-scanner to determine the correlation between impact energy and delamination area. The energy absorbed by a quasi-isotropic specimen having four interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy of a hybrid specimen embedding GFRP (Glass-fiber reinforced plastics) layer was higher than that of normal specimens. Also, a falling weight impact tester was built to evaluate the characteristics and impact strength of CFRPs.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.179-182
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• 2001

Impacter tester was build of to evaluate the characterization of non-flamable Glass/phenol laminate plates under the low velocity impact. The damage of composite laminates are matrix cracking, delamination, and fiber breakage for impact energy. In this study, this is to find impact properties of Glass/phenol in used in a forehead part of lighting subway. To determine impact damage characteristics which is made in a laminate, use the UT C-scan after- macrography. And then evaluated the reduction of strength in a rate of impact energy with CAI(Compression After Impact) test

• Journal of the korean Society of Automotive Engineers
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• v.10 no.2
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• pp.46-53
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• 1988

Effect of Notch Shape and Hardness Ratio on Characteristics of Impact Fracture in Dual Phase Steels. In this study, it is investigated the effect of notch shape and hardness ratio on the characteristics of impact fracture in dual phase steels. The impact test was carried out at the temperature range from -40.deg. C to room temperature with Instrumented Charpy Impact Tester. The main results obtained are as follows; 1, The maximum impact bending strength (.sigma.$_{max}$) increases with the tensile strength. Also, the impact energy depends on .sigma.$_{max}$. 2, In room temperature, the impact energy depends on crack-initiation energy (E$_{i}$) in case of the high hardness ratio (R=3.4), whereas depends on crack-propagation energy (E$_{p}$) in case of the low hardness ratio (R=1.8) and the dependence of crack-initiation energy of the impact characteristics decreases with increasing test temperature. These phenomena are result from the difficulty of cleavage facet formation.ion.ion.

• Journal of the Korean institute of surface engineering
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• v.35 no.6
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• pp.408-414
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• 2002

TiN and TiAlN coating layer were deposited on WC-Co steel substrates by an arc ion plating(AIP) technique. The crystallinity and morphology for the deposited coating layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The impact behaviors of the deposited TiN and TiAlN coating layer were investigated with a ball-on-plate impact tester. Beyond $10^2$ impact cycle, TiAlN coating layer showed superior impact wear resistance compared to TiN coating layer. On the other hand, both TiN and TiAlN coating layers started to be partially failed between $10^2$ and $10^3$ impact cycle. Above $10^3$ impact cycle, TiN and TiAlN coating layers showed similar impact behavior because of the substrate effect.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.441-446
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• 2004

Mechanical systems with rubber parts have been used widely in industry fields. The evaluation of the physical characteristics of rubber is important in rubber application. Rubber material is useful to machine component for excellent shock absorbing characteristics. The impact characteristics of rubber were examined by experimental and finite element method. The impact test was conducted with a free-drop type impact tester. The ABAQUS/Explicit was used for finite element analysis. The effects of thickness and diameter of the cylindrical rubber structures were investigated. The impact absorbing ratio of the rubber material was studied order to compare the peak reaction force of the specimen which only contained aluminum against the specimen with the inserted rubber part.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.52-63
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• 1998

The impact programmer for impact test was designed and the impact analysis was conducted. The effects of the material and geometric parameters on the impact force and pulse shape were investigated. The impact characteristics were examined by experimental and finite element method. The impact test was conducted with free drop impact tester. The ABAQUS/Explicit 5.5 version was used for finite element analysis. The geometric parameters of the conical and dome type impact programmer were analyzed. The polyurethane impact programmers were fabricated and tested. The effects of the hardness and thickness of the impact programmer were studied. The peak acceleration and time duration of impact programmer have close correlation with the hardness, impact energy and thickness of the impactor. The experiment was good agreement with analytical predictions. The impact pulse shape generated with polyurethane impact programmer was half sine shape. The maximum impact force was proportional to impact energy. The impact acceleration was decreased with thickness of impact programmer. The maximum impact time duration level was about 2 msec.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.27-30
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• 2005

This paper studied the PVDF(polyvinylidene fluoride) and Acoustic Emission sensors characteristics of the laminated composite panels under the low velocity impact. The various impact test by changing impact height is performed on the instrumented drop weight impact tester. The STFT(short time Fourier transform) and WT(wavelet transform) are used to decompose the each sensor signals. A ultrasonic C-scan and digital scope are used to define damaged area in each case. The test result indicated that the individual sensor signals involve the damage initiation and development.