• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.04a
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• pp.1.1-4
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• 1999

The toughening mechanism and fracture behavior of rubber/polymer composites were investigated with respect to two factors; (1) the composition ratio of polymers(PPO and PS which have a different chain flexibility) and (ii) the rubber particle size in PPO/PS blend system Izod impact test and fractographic observation of the fracture surface using scanning electron microscope were conducted, Finite element analysis were carried out to gain understanding of plastic deformation(shear yielding and crazing) of these materials.

• The Korean Journal of Rheology
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• v.3 no.1
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• pp.30-37
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• 1991

제 2세대 bismaleimide의 일종인 Boots Technochemie 사의 Compimide 800을 매트 릭스 수지로 선정하여 여기에 촉매(DABCO 0.2wt%) 및 반응성 내충격성 증진제(TM 120; 15. 30, 60 part)를 첨가하여 Carbon/BMI 적층판($\pm$ 45。)2s를 만들어 인장 시험을 하여 in-plane shear하에서의 파단특성을 조사하였다, 이경우에 전단 탄성율을 망목상구조의 특성 에 의해 좌우되고 전단강도는 파단면의 형태와 밀접합 관계가 있다. TM 120을 30 part 첨 가한 경우의 전단강도가 가장 우수하였다

• Polymer(Korea)
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• v.29 no.3
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• pp.231-236
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• 2005

Amino terminated polyetherimide (AP-PEI) has been synthesized using 2,2'-bis [4-(3,4-dicarboxyphenoxy)-phenyl]propane dianhydride (BPADA) and m-phenylenediamine. Polyetherimide containing pendant carboxy group (CP-PEI) has also been synthesized by the reaction of BPADA, m-phenylenediamine and 3,5-diaminobenzoic acid. The modified PEIs were used as toughening agent for diglycidyl ether of bisphenol-A epoxy resin which was cured with nadic methyl anhydride (NMA). Thermal properties, fracture toughness ($K_{IC}$) and solvent resistance of toughened epoxy resin were measured. The $K_{IC}$ of epoxy resin containing 20 phr of AT-PEI was 2.88$MPa{\cdot}m^{0.5}$ without sacrificing thermal properties. The $K_{IC}$ of epoxy resin which contained 20 phr of CP-PEI was 2.82$MPa{\cdot}m^{0.5}$.

• Journal of Korea Foundry Society
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• v.10 no.4
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• pp.299-308
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• 1990

Ductile cast iron has a good ductility and ductility and toughness than those of gray cast iron, because the shape of graphite is spheroidal. It has been reported that the strengthening and toughening of the ductile cast iron was resulted from the good modification of various matrix structures obtained by the heat treatment or addition of alloying elements. This study aims to investigate the effect of various special heat treatment(Cyclic Heat Treatment, Intermediate Heat Treatment, Step Quenching), austempering and alloying element(Ni) on the strength and toughness of ductile cast iron. The results obtained from this study are summarized as follows. 1) With addition of Ni, the amount of pearlite or bainite were increased and the morphologies of pearlite or bainite became finer by special heat treatments. 2) As the Ni added and not added ductile cast iron were treated by austenitizing at $900^{\circ}C$ and $840^{\circ}C$, in the latter the austenite was mostly formed in the vicinity of eutectic cell boundary, but in the former on the whole matrix. 3) In cyclic heat treatment, the volume fraction of pearlite was increased and the shape of pearlite was fined with increase of the number of cycle. 4) The shape of pearlite was mostly bar type in the intermediate heat treatment, but spheroidal type in step quenching. 5) The mechanical properties of ductile cast iron containing 1.5%Ni austempered at $400^{\circ}C$ for 25min. after austenitizing at $900^{\circ}C$ for 15min. were a good value of hardness 105(HRB), impact energy 12.5(kg.m), tensile strength 112($kg/mm^2$) and elongation 6.8(%).

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.936-941
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• 2001

The influence of the ${Al_2}{O_3}$ particle size on flaw tolerance of the $ZrO_2/{Al_2}{O_3}$ composites prepared by mixing 5.31 mol% ${Y_2}{O_3}$-4.45 mol% ${Nb_2}{O_5}$-90.31 mol% $ZrO_2$ and ${Al_2}{O_3}$ was investigated. The composites exhibited rising R-curve behavior and plateau fracture toughness of 7.9 and $8.8MPam^{1/2}$ for the additions of 20 vol% of 0.2 and $2.8{\mu}m$ ${Al_2}{O_3}$ particles, respectively. The difference in the fracture toughness resistance was attributed mainly to the grain size of tetragonal $ZrO_2$ phase in the composites, which scaled with the ${Al_2}{O_3}$ particle size.

• Journal of Adhesion and Interface
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• v.3 no.4
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• pp.19-26
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• 2002

In order to study the toughening mechanism of rubber modified polycarbonate, the sequence of development of micro-voids was investigated by real-time small angle X-ray scattering with Synchrotron radiation (SR-SAXS). The used test method was wedge test. The scattering intensity increases with increasing penetration depth of wedge, i.e. applied strain. The increase is due to the micro-void formation during deformation. This micro-void was uniformly developed in matrix and was different from large-void due to internal cavitation of rubber particle and/or debonding between rubber particle and polycarbonate matrix. The micro-void was developed at the critical strain and the radius of micro-void is around $600{\AA}$. Above the critical strain the size of micro-void remains almost constant with increasing applied strain. However, the population of micro-void increased with applied strain.

• Elastomers and Composites
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• v.56 no.3
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• pp.179-186
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• 2021

Carbon-based nanofillers, including nanodiamond (ND) and carbon nanotubes (CNTs), have been employed in epoxy matrixes for improving the toughness, using the tow prepreg method, of epoxy compounds for high pressure tanks. The reinforcing performance was compared with those of commercially available toughening fillers, including carboxyl-terminated butadiene acrylonitrile (CTBN) and block copolymers, such as poly(methyl methacrylate)-b-poly(butyl acrylate)-b-poly(methyl methacrylate) (BA-b-MMA). CTNB improved the mechanical performance at a relatively high filler loading of ~5 phr. Nanosized BA-b-MMA showed improved performance at a lower filler loading of ~2 phr. However, the mechanical properties deteriorated at a higher loading of ~5 phr because of the formation of larger aggregates. ND showed no significant improvement in mechanical properties because of aggregate formation. In contrast, surface-treated ND with epoxidized hydroxyl-terminated polybutadiene considerably improved the mechanical properties, notably the impact strength, because of more uniform dispersion of particles in the epoxy matrix. CNTs noticeably improved the flexural strength and impact strength at a filler loading of 0.5 phr. However, the improvements were lost with further addition of fillers because of CNT aggregation.

• Journal of the Korean Ceramic Society
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• v.36 no.10
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• pp.1123-1131
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• 1999

Alumina-glass composites which are considered as the material of the choice for all dental crown was prepared by aqeous-based tape casting and sintering for 2h at 1120$^{\circ}C$ followed by glass infiltration for 2h at 1100$^{\circ}C$ Biaxial strength and fracture toughness of the composites were evaluated to determine the optimum composition of the tape as a function of the amount of constituent such as alumina binder and plasticizer. The strength and the fracture toughness of the alumina tape increased with increasing the contents of alumina and binder. These observations are consistent with in fluence of the constituents on mean alumuna particle distance in tapes suggesting that high strength of the glass infiltrated alumina composites is related to toughening by crack bowing. The biaxial strength and the fracture toughness of the composite containing the optimum constituent composition were 523 MPa and 3.3 MPa$.$1/2 respectively.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1990.11a
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• pp.16-35
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• 1990

The mechanism of failure of lubricated surfaces at high sliding speeds was Investigated. Experiments were performed with the ball-on-flat and cylinder-on-flat geometries, using lubricants of four different chemical reactivities. Surface failure was found to not be predictable using the ratlo, $\lambda$, of fluid film thickness to composite surface roughness except when chemically inert lubricants are used. Even then the influence of temperature rise on fluid film thickness does not adequately explain the low load carrying capacity of lubricants at high sliding speeds. which causes surface failure. The protective layers on sliding surfaces that form by chemical reaction with the lubricant were found to reduce the surface roughentrig and Increase the load carrying capacity of surfaces to values of $\lambda$ as low as 0.03. Neither the surface toughening nor the formation of the protective layers have been incorporated Into failure models for lubricated systems.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.142-149
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• 2003

Domain switching effect on crack growth in ferroelectric ceramics under combined electric and mechanical loading is investigated. The shape and size of the switching zone is shown to depend strongly on the relative magnitude between the applied electric field and stress field as well as on the ratio of the coercive electric field to the yield electric field. The toughening mechanism is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. Crack-tip stress intensity factor induced by domain switching for the steady state crack growth is numerically obtained.