• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.10a
• /
• pp.261-264
• /
• 2002

Interfacial evaluation, damage sensing and cure monitoring of single carbon fiber/thermosetting composite with different curing processes was investigated using electro-micromechanical test. After curing, residual stress was monitored by measurement of electrical resistance (ER) and then it was compared to correlate with various curing processes. In thermal curing, curing shrinkage appeared significantly by matrix shrinkage and residual stress due to the difference in thermal expansion coefficient (TEC). The change in electrical resistance (ΔR) on thermal curing was higher than that on ultraviolet (UV) curing. For thermal curing, apparent modulus was the highest and reaching time until same strain was faster. So far thermal curing shows strong durability on the IFSS after boiling test.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.49 no.5
• /
• pp.23-30
• /
• 2007

This research was to evaluate the shrinkage and durability performance of latex modified repair mortar and to improve the service lift of the agricultural concrete structures. The shrinkage characteristics of the repair material creates the delamination of repair materials and existing concrete. It may reduce the service life of structures. Also the reduction of durability performance of the repair materials induces the destruction of the repaired concrete structures at early stage. In this research, plastic and drying shrinkage, thermal expansion coefficient for shrinkage properties, durability performance, permeability, repeated freezing and thawing, and resistance of chemical solution test were performed. Test results showed that the latex modified repair mortar indicated the shrinkage amount which the delamination does not happen, and the latex modified repair mortar appeared excellent long-term durability performance which can increase the service life.

• Polymer(Korea)
• /
• v.26 no.3
• /
• pp.335-343
• /
• 2002

Blend resin (PET/PETG 70/30 blend) of poly (ethylene terephthalate) (PET) and poly (ethylene terephthalate glycol) (PETG) of weight percent 70/30 was prepared by a twin-screw extruder. Undrawn films of the blend and pure PETG were made by melt-press in hot press. Drawn films were made by capillary rheometer. Crystallinity, shrinkage, thermal, dynamic mechanical, and mechanical properties of these blends and PETG drawn films were investigated by wide angle X-ray diffractometer, dry oven, DSC thermal analyzer, and tensile tester. The crystallinity and density of these films increased with increasing draw ratio and draw rate but decreased with increasing draw temperature. The crystallinity and density of the blend films were higher than those of PETG films. The tensile strength and tensile modulus of these drawn alms increased with increasing draw ratio and draw rate but decreased with increasing draw temperature. The tensile strength and tensile modulus of blend films were higher than those of PETG films. Shrinkage of PETG md blend films decreased with draw ratio and draw rate. Shrinkage of undrawn blend film was 600% higher than that of pure PET film.

• Journal of Welding and Joining
• /
• v.31 no.6
• /
• pp.37-43
• /
• 2013

This study targets to make clear the connection between MS (Martensite start) point and welding shrinkage. We approved that a Martensite-transformed weldment may not yield state under low MS point, but also admitted the limitation of numerical calculation by inherent strain approach or thermal strain approach. Therefore, new thermal strain formulae during cooling stages were made. As a thermal strain is obtained by integrating thermal extension coefficient, a constant of integration should be decided. In our suggested formulae, the origin was based on totally remained austenite, and added strain from volume changes in Martensite transformation was based on totally transformed ferrite. Through the suggested methodology, It is verified that an MS point under a critical temperature can let weld shrinkage relax and the critical value can be obtained. For supporting this process, 15 weld-consumables were made, were tested by fillet type and were measured. As a result, a positive correlation between MS point and level of weld-distortion was obtained, but it was rather weak.

• Fire Science and Engineering
• /
• v.2 no.1
• /
• pp.11-20
• /
• 1988

The success of analyzing the behavior of reinforced concrete structures at elevated temperature greatly depends on how accurately certain thermal properties, especially thermal expansion, specific heat and density thermal conductivity can be determined in a wide temperature range. In this Paper, in order to Predict the behavior of reinforced concrete structure in fire hazards thermal expansion characteristics of normal concrete are formulated through experimental investigation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.545-548
• /
• 2004

This paper is to investigate the shrinkage properties of high performance concrete (HPC) with mixture adjustment by using mock-up specimens. HPC with mixture adjustment needed a higher dosage of SP agent due to fluidity reduction and a larger dosage of AE agent due to the reduction of air content. Setting time of HPC with mixture adjustment exhibited earlier than that of control HPC by as much as 6 hours. HPC with mixture adjustment gained more than 70MPa of compressive strength. Autogenous shrinkage of Control HPC was found to be $-340\times40^{-6}$ at 49days when the expansion value by thermal effect was excluded and HPC with mixture adjustment $-175\times10^{-6}$, which was the half of the value of control HPC. Drying shrinkage of center section of HPC with mixture adjustment showed similar tendency with autogenous shrinkage because of no internal moisture movement, while surface section had larger drying shrinkage. The specimen embedded with reinforcing bar had smaller deformation caused by confinement of reinforcing bar.

• Textile Coloration and Finishing
• /
• v.10 no.3
• /
• pp.10-19
• /
• 1998

This paper investigates the change of mechanical properties and thermal shrinkage in commercial multi-filament PET(polyethylene terephthalate) , namely, regular yarn, POY, DTY and composite yarn. To determine changing the effects of processing steps, these were examined at three steps process simulation conditions. The first step is sizing simulation$(S-1\;step\;:\;130^\circ{C}\times2\;min$., hot air treatment under 0.1 gf/d load), the second step is scouring simulation$(S-2\;step\;:\;100^\circ{C}\times20\;min$., boiling water treatment under free tension)and final step is setting simulation$(S-3\;step\;:\;180^\circ{C}\times2\;min$., hot air treatment under free tension). Regular yarn in multi-step treatment showed higher shrinkage at S-3 step and DTY showed higher in at S-1 step. While POY was relaxed at S-1 step, composite yarn showed different shrinkage properties depending on composite yarn type. Mechanical properties showed good relationship with shrinkage : high shrinkage makes initial modulus decrease and bleating strain increase. It also makes decreasing yield strain and yield stress decrease.

• Korean Journal of Materials Research
• /
• v.12 no.7
• /
• pp.580-586
• /
• 2002

The effect of processing and designing variables such as pouring temperature(1400 or $1500^{\circ}C$), inoculation and risering design(T and H type) on the formation of defects such as external depression, primary and secondary shrinkage cavities in GC150 gray cast iron was investigated. In T type risering design, external depression or primary shrinkage cavity due to liquid contraction was formed in all of the eight cases. Regardless of its modulus value, the riser could not function properly in T type risering design because directional solidification was not promoted toward the riser. On the other hand, the four cases of H type risering design in which thermal sleeves were set onto the risers produced defect-free castings. In both types of the risering designs, secondary shrinkage cavity caused by solidification contraction was not observed in the casting because of the expansion pressure due to graphite precipitation and the application of rigid pep-set mold. The degree of external depression or primary shrinkage cavity was reduced with lowered pouring temperature. The effect of inoculation was diminished because of the high carbon equivalent of GC 150 gray cast iron.

• Textile Coloration and Finishing
• /
• v.16 no.6
• /
• pp.35-43
• /
• 2004

This study surveys the physical properties of ATY produced with FDY and POY. ATY is made with 70d Nylon FDY and 80d Nylon POY using AIKI air jet texturing machines, respectively. The processing parameters such as air pressure and yam speed are varied, and air pressure is varied ranging with 8.5bar, l0.5bar and 1l.5bar, and yarn speed is varied ranging with 400m/mim, 450m/mim, and 500m/min. The various physical properties of ATY made by POY and FDY denier, wet shrinkage, dry shrinkage, tensile properties, thermal stress and instability are measured and discussed with air pressure and yam speed. The shrinkage simulation of ATY is performed for analysing the process shrinkage on the dyeing and finishing processes.

• Steel and Composite Structures
• /
• v.6 no.2
• /
• pp.123-138
• /
• 2006

This paper proposes a model for the analysis of the construction sequences of steel-concrete composite decks in which the slab is cast-in-situ for segments. The model accounts for early age shrinkage, such as thermal and endogenous shrinkage, drying shrinkage, tensile creep effects and the complex sequences of loading due to pouring of the different slab segments. The evolution of the structure is caught by suitably defining the constitutive relationships of the concrete and the steel reinforcements. The numerical solution is obtained by means of a step-by-step procedure and the finite element method. The proposed model is then applied to a composite deck in order to show its potential.