• Composites Research
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• v.32 no.1
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• pp.50-55
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• 2019

In this study, we investigated the effect of fiber alignment in helicoidal structure on the mechanical properties of biomimetic fiber-reinforced composites. Using finite element analysis, circular biomimetic fiber composites were designed and studied. Various amounts of pressure loads were applied to a surface of the composites, and then bending and failure behaviors of the composites were analyzed. The results showed various failure morphologies according to the orientation of the fibers, and it turned out that the fiber alignment in helicoidal structure significantly improved the bending strength of the composite under pressure loading. This was because the fiber alignment in various directions for each layer dispersed effectively the fracture energy from the external load into multiple directions.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.515-521
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• 1997

The effects of heat treatment and fiber orientation on tensile strength and fatigue behavior were studied in a continuously reinforced. magnesium-based composite Following an earlier TEM investigation, specimens were thermally aged to modified the interfacial zone between the alumina fibers and the magnesium alloy matrix. From the tensile experimental results, the ultimate tensile strength of the aged specimens were lower than that of the as-fabricated due to weak fiber-matrix interfacial strength with chemical reaction during the thermal processing. The fatigue crack growth experiments were conducted with specimens having the fiber orientation normal to the crack growth direction (longitudinal) and also specimens with the fibers oriented parallel to the crack growth direction(transverse). A comparison of the fatigue crack growth behavior indicates that aged longitudinal specimens are more resistant to fatigue crack growth the as-fabricated longitudinal specimens. Conversely, as-fabricated transverse specimens are more resistant to fatigue crack growth than aged transverse specimens.

• Journal of Power System Engineering
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• v.7 no.1
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• pp.25-33
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• 2003

섬유강화 복합재료의 계면 강도는 강화재와 메트릭스간의 계면특성, 강화용 섬유의 표면처리 및 섬유간의 거리 등에 많은 영향을 받는다. 본 연구에서는 섬유간의 거리가 섬유강화 복합재료의 계면특성에 미치는 영향을 고찰하기 위해, E glass fiber/epoxy 복합재료의 시험편을 제작하고, 섬유의 표면처리 및 섬유파괴가 이웃하는 섬유파괴에 영향을 미치는 거리에 대해 고찰하였다. E glass fiber/epoxy 복합재료의 계면 전단강도는 섬유간 거리 $0{\sim}50{\mu}m$ 사이에서는 섬유의 표면처리와는 관계없이 섬유간 거리가 증가할수록 증가하였고, 섬유간 거리 $50{\mu}m$ 이상에서는 섬유간거리에 관계없이 계면전단강도는 일정하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.210-210
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• 2003

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.381-389
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• 2000

Metal matrix composite(MMCs) have been rapidly becoming one of the strongest candidates for structural materials for high temperature application. It is well recognized that MMCs always experience at least one large cool-down from processing temperature before my significant applied service loading. Due to the large difference in thermal expansion coefficient between the fiber and matrix, large thermal residual stresses generally develop in composites. It was reported from many previous studies that the effects of thermal residual stress on mechanical properties and fracture behavior were much more complex and dramatic than conventional engineering materials. Therefore it is crucial to evaluate the effect of heat treatment which changes the characteristic of distribution of thermal residual stress in MMCs. Single fiber composite(SFC) test based on the balance in a micromechanical model is a quite convenient method to evaluate interfacial shear strength(IFSS) and the failure mode of composite. In this study the effect of heat treatment on IFSS and the microscopic failure mechanism of MMC is investigated by combining acoustic emission(AE) technique with SFC test. The characteristic of AE signal, IFSS and microscopic failure mechanism due to heat treatment condition is discussed.

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.435-438
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• 1998

Textile composites란 직물, 편성물, 브레이드 등을 사용한 섬유강화 복합재료의 총칭으로서 텍스타일이 지닌 뛰어난 기능을 매트릭스에 부가함에 따라 단일재료로는 얻지 못하는 뛰어난 공업재료를 만들 수 있다. 편성물은 직물이나 브레이드에 비해서, 변형특성도 매우 우수하고 고생산성이다. 복합재료에서 강화재로 편성물을 사용하는 경우, 섬유소재, 편조직, 편환 밀도 등을 고려하는 것에 의하여 편성물 강화 복합재료의 역학적 특성이 달라진다. (중략)

• Composites Research
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• v.18 no.6
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• pp.1-8
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• 2005

The fiber-reinforced composite materials have been advanced for various applications because of their excellent mechanical and electromagnetic properties. On their manufacturing processes, however, thermo-curing inherently produces the undesired thermal deformation mainly from temperature drop from the process temperature to the room temperature, so called spring-back. The spring-back must be understood especially in the hybrid composites in order to design and fabricate desired shape. In this research, (glass fiber / epoxy) + (carbon fiber / epoxy) unsymmetric hybrid composites were fabricated under various conditions such as cure cycle, laminate thickness, stacking sequence and curing sequence. Coupons were made and spring-back were measured using coordinate measuring machine (CMM). Using the Classical Lamination Theory (CLT) and finite element analysis (ANSYS), the behavior of spring-back were predicted and compared with the experimental data. The results from CLT and FEA agreed well with the experimental data. Although, the spring-back could be reduced by lowering curing temperature, at any case, the spring-back could not be removed completely.

• Korean Journal of Materials Research
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• v.7 no.11
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• pp.951-956
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• 1997

Vacuum Hot Pressing을 이용하여 제조한 TiNi형상기억섬유 강화 6061 AI기지 복합재료를 제조하고 미세조직 및 기계적 특성 등을 연구하였다. 제조된 복합재의 항복응력은 예비변형량, 섬유체적율 및 열처리에 따라 증가하였다. 복합재의 지적특성은 예비변형이 가하여진 후 재가열되었을 때 기지 내 TiNi 섬유의 형상기억효과에 의한 압축잔류응력 발생에 기인된다. 미세조직 관찰 섬유와 기지 사이에는 AI$_{3}$Ti및 AI$_{3}$Ni의 금속간화합물층이 관찰되었다. 또한 시험온도 증가와 더불어 TiNi섬유강화된 복합재의 유동강도는 높은 값을 나타내었다.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.330-333
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• 2001

일반적으로 하나 또는 그 이상의 입자상 충전재 흑은 섬유상 강화재와 연속상인 고분자 기재로 이루어진 고분자 복합재료는 물성이나 기능이 더욱 더 우수한 고성능/고기능성 고분자 재료에 대한 수요가 급격히 증대됨에 따라 이에 대한 많은 연구가 행해지고 있다[1,2]. 그러나 고분자 복합재료의 응력전달은 강화재와 고분자 기재의 계면을 통하여 일어나게 되므로 복합재료의 기계적 물성 등은 충전재의 양, 입자의 크기, 표면성질 뿐만 아니라 강화재와 고분자 기재 사이의 계면 접착력 또는 계면 성질에 크게 좌우된다. (중략)

• Composites Research
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• v.27 no.2
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• pp.52-58
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• 2014

Short fiber reinforced composites manufactured by injection molding have diverse fiber orientations variable with measuring positions even in the same specimen, which is caused by the flow induced fiber orientation. Fiber orientations considerably affect the mechanical and thermal properties of final composite products. In this study, fiber orientation of injection molded carbon fiber reinforced PA6/PPO composite was measured at several points of the specimen by optical microscopy analysis and the corresponding izod impact strength, coefficients of thermal expansion (CTE) were also measured to investigate the influence of local fiber orientation on the mechanical and thermal properties. Izod impact strength where fiber was perpendicular to the direction of crack propagation was higher than where fiber was parallel to the direction, which could be explained be the impact resistance reinforcing mechanism by fiber orientation. CTE was also lower where fiber was parallel to the measurement direction of CTE than where fiber was perpendicular to the direction, which could be also explained by the dimensional stability mechanism by fiber orientation.