• Journal of Mechanical Science and Technology
• /
• 제16권2호
• /
• pp.192-202
• /
• 2002

In particle or short-fiber reinforced composites, cracking of the reinforcements is a significant damage mode because the cracked reinforcements lose load carrying capacity. This paper deals with an incremental damage theory of particle or short-fiber reinforced composites. The composite undergoing damage process contains intact and broken reinforcements in a matrix. To describe the load carrying capacity of cracked reinforcement, the average stress of cracked ellipsoidal inhomogeneity in an infinite body as proposed in the previous paper is introduced. An incremental constitutive relation on particle or short-fiber reinforced composites including progressive cracking of the reinforcements is developed based on Eshelby's (1957) equivalent inclusion method and Mori and Tanaka\`s (1973) mean field concept. Influence of the cracking damage on the stress-strain response of composites is demonstrated.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1998년도 추계학술대회 논문집
• /
• pp.287-292
• /
• 1998

In particle or short-fiber reinforced composites. cracking of the reinforcements is a significant damage mode because the broken reinforcements lose load carrying capacity. This paper deals with the load carrying capacity of intact and broken ellipsoidal inhomogeneities embedded in an infinite body and a damage theory of particle or short-fiber reinforce composites. The average stress in the inhomogeneity represents its load carrying capacity. and the difference between the average stresses of the intact t and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The composite in damage process contains intact and broken reinforcements in a matrix. An incremental constitutive relation of particle or short-fiber reinforced composites including the progressive cracking damage of the reinforcements have been developed based on the Eshelby's equivalent inclusion method and Mori and Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated.

• Advances in materials Research
• /
• 제4권2호
• /
• pp.97-111
• /
• 2015

Polypropylene short fiber (PP)-clay particulate-epoxy ternary composites were prepared by reinforcing PP short fiber and clay particles in the range of 0.1 phr to 0.7 phr into epoxy resin. Prepared hybrid composites were characterized for their mechanical, thermal and flame retardant properties. The obtained results indicated an increase in impact resistance, tensile strength, flexural strength and Young's modulus to an extent (up to 0.5 phr clay and 0.5 phr PP short fiber) and then decreases as the reinforcing phases are further increased. The thermal stability of these materials are found to increase up to 0.2 phr clay and 0.2 phr PP addition, beyond which it is decreased. Addition of clay is found to have the negative effect on epoxy-PP short fiber composites, which is evident from the comparison of mechanical and thermal properties of epoxy-0.5 phr PP short fiber composite and epoxy-0.5 phr PP short fiber-0.5 phr clay composite hybrid. UL-94 tests conducted on the composite hybrids have showed a reduction in the burning rate. Morphological observations indicated a greater fiber pull with the addition of clay. The performed tests in the present study indicated that materials under investigation have promising applications in construction, agriculture and decorative purposes.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 추계학술발표대회 논문집
• /
• pp.61-63
• /
• 2001

Residual stress distribution in injection-molded short fiber composites was determined using layer-removal method. Polysterene with 3 vol% carbon fibers was injection-molded into the tensile specimen. With milling machine layer-removal process was conducted and the curvature data were acquired. Treuting and Read analysis which is assuming isotropic material, and White analysis considering anisotropy due to the fiber orientation were used to calculate residual stress of the flow direction through the thickness direction and compared with each other.

• Archives of Metallurgy and Materials
• /
• 제66권4호
• /
• pp.941-946
• /
• 2021

A356 Al composites reinforced by short carbon fiber were prepared through the 2-step process: fabrication of a composite precursor and ultrasonication of the precursor melt. The short carbon fibers were coated with 0.15~1.5 ㎛ thick SiC layer by a carbothermal reaction, and an amount of the carbon fiber reinforcement was determined to be 1.5 vol.% and 4.0 vol.%, respectively. The addition of the carbon fiber increased the hardness of A356 alloy. However, tensile strength did not increase in the as-cast composites regardless of the SiC coating and volume fraction of the carbon fiber, due to the debonding which reduced load transfer efficiency from matrix to fiber at the interface. After T6-treatment of the composites, a significant increase in strength occurred only in the composite reinforced by the SiC-coated short carbon fiber, which was considered to result from the formation of a precipitate improving the Al/SiC interfacial strength.

• 대한기계학회논문집A
• /
• 제24권1호
• /
• pp.250-258
• /
• 2000

The reinforcing effects of ductile short-fiber reinforced brittle matrix composites are studied by, measuring flexural strength, fracture toughness and impact energy as functions of fiber volume fraction and length. The parameters of fracture mechanics, K and J are applied to assess fracture toughness and bridging stress. It is found that fracture toughness is greatly, influenced by the bridging stress ill which fiber pull-out is occur. For the reinforcing effects as functions of fiber volume fraction($V_f$ = 1, 2, 3 %) and length(L = 3, 6. 10cm), the flexural strength is maximum at $V_f$ = 1% and both fracture toughness.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.201-204
• /
• 2001

A Confocal Laser Scanning Microscope (CLSM) is applied to determine three-dimensional fiber orientation states in injection-molded short fiber composites. Since the CLSM optically sections the composites, more than two planes either on or below the surface of composites can be obtained. Therefore, three dimensional fiber orientation states are determined without destruction. To predict the orientation states, velocity and temperature fields are calculated by using a hybrid FEM/FDM method. The change of orientation state during packing stage is also considered by employing a compressible Hele-Shaw model. The predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from other effects, which are not considered in the numerical analysis.

• 한국주조공학회지
• /
• 제13권6호
• /
• pp.547-554
• /
• 1993

Aluminum alloy matrix composites reinforced with various amounts of $Al_2O_3$ short fibers have been produced by rheo-compocasting accompanied by hot pressing. When composites reinforced with fibers are produced by rheo-compocasting, S-L process is the most effective method for homogeneous dispersion of fibers. A sound composites with the improved orientation(3 dimension${\rightarrow}$2 dimension) of the fibers and increased volume fraction of them have been fabricated through the hot pressing of the casted composites. Fibers are broken down when rheo-compocasting, hot pressing, and $T_6$ treating. Among them fibers are broken down most heavily in the hot pressing. And even in the case of the composite reinforced with 30 vol% fibers, which showed the hardest fiber break down, aspect ratio(11.6) is higher than critical aspect ratio(10.7). The fiber strengthening effect in the composites has showed upto 573K. As the test temperature increases to the range of 573K, the effect has been higher. The fracture of composites is controlled by fiber from room temperature to 473K, but the fracture of composites is controlled by interface between fiber and matrix alloy above 473K.

• 한국주조공학회지
• /
• 제17권1호
• /
• pp.28-35
• /
• 1997

SiC whisker and $Al_2O_3-SiO_2$ short fiber reinforced AC8A, AC8B and AC8B(J) marix composites were fabricated by squeeze casting method. Preform deformation, change of reinforcement volumefraction and formation of macro-segregation in two composites were investigated by using micro Vickers hardness test, analysis of macro and micro structures with OM, SEM and EDAX. $Al_2O_3-SiO_2$ short fiber preform manufactured with 5% $SiO_2$ binder in this study was considerably deformed and cracked, nevertheless, the short fibers were distributed homogeneously in the composites. In SiC whisker reinforced composites, on the other hand, preform deforming and cracking were not occurred, however, macro segregation zone formed along the infiltration routes by interface reaction during infiltration of molten metal into the preform was observed at center-low area in the composites. The decrease of hardness in the macro segregation zone resulted from the depletion of Si and Mg atoms.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
• /
• pp.122-126
• /
• 2000

In particle or short-fiber reinforced composites cracking of the reinforcements is a significant damage mode because the broken reinformcements lose load carrying capacity . The average stress in the inhomogeneity represents its load carrying capacity and the difference between the average stresses of the intact and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The composite in damage process contains intact and broken reinforcements in a matrix, An incremental constitutive relation of particle or short-fiber reinforced composites including the progressive cracking damage of the reinforcements have been developed based on the Eshelby's equivalent inclusion method and Mori-Tanaka's mean field concept. influence of the cracking damage on the Eshelby's equivalent inclusion method and Mori-Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated.