(A) study on delamination toughness of carbon fiber/epoxy composite with chopped kevlar fiber and nylon-6 powder reinforcement = 탄소섬유/에폭시 복합 재료의 Kevlar 단 섬유 및 나이론-6입자가 첨가된 층간 파괴 특성에 관한 연구

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Advanced composite materials have been broadly used for both military and aerospace application. Their high specific modulus and specific strength make them attractive candidates for structural materials. However, as a result of poor out-of-plane strength, brittle composites such as carbon-fiber-reinforced epoxy, exhibit restricted impact strength, low damage tolerance, and poor delamination resistance. Several approaches have been developed to improve the impact toughness and interlaminar fracture toughness of composites. In this study, short Kevlar fiber (SKF) and/or Nylon-6 powder (N6P) was spread in the mid-plane of the continuous-carbon-fiber/epoxy laminate before processing where the initial crack is introduced. The extreme case of SKF/epoxy interface. was obtained by $O_2$-plasma SKF (P-SKF) or silicon release agent SKF (S-SKF). Mode I ($G_{IC}$) and Mode II ($G_{IIC}$) interlaminar fracture toughness of carbon-fiber/epoxy composites have been investigated as a function of amount of SKF and/or N6P between continuous fiber layers with different surface condition of SKF. The fracture surface was studied using scanning electron microscopy (SEM) and optical microscopy. Interfacial shear strength of SKF/epoxy interface was determined by Kevlar fiber pull-out test. Surface chemistry of SKF, P-SKF and S-SKF was examined by ESCA and FT-IR. $G_{IIC}$ increased with increasing crack length as a consequence of the presence of SKF``s bridging in the wake of propagating crack. $G_{IIC}$ of SKF alone could reach the maximum at intermediate amount of SKF. $G_{IIC}$ of SKF and N6P was lower than that of SKF alone because N6P prevented the orientation of SKF to out-of-plane. The extent of SKF``s bridging phenomenon may be influenced by the amount and orientation of SKF. $G_{IC}$ showed no significant effect with SKF and uniform irrespective of crack length. Scanning electron microscopy (SEM) after $G_{IIC}$ test showed that new surfaces were created by extensive fi...
Advisors
Kim, Sung-Chulresearcher김성철researcher
Description
한국과학기술원 : 화학공학과,
Publisher
한국과학기술원
Issue Date
1997
Identifier
113021/325007 / 000925126
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 화학공학과, 1997.2, [ x, 119 p. ]

Keywords

Nylon; Kevlar; Composite; Fracture toughness; 충격강성; 나이론; 케브라; 복합재료

URI
http://hdl.handle.net/10203/28744
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=113021&flag=dissertation
Appears in Collection
CBE-Theses_Ph.D.(박사논문)
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