국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	Comparison of Intralaminar and Interlaminar Mode-I Fracture Toughness of Unidirectional IM7/8552 Graphite/Epoxy Composite
저자	Czabaj, Michael W.;; Ratcliffe, James
Keyword	CANTILEVER BEAMS;; CRACK INITIATION;; CRACK PROPAGATION;; DELAMINATING;; FATIGUE (MATERIALS); FATIGUE TESTS;; FRACTOGRAPHY;; FRACTURE STRENGTH;; GRAPHITE-EPOXY COMPOSITES;; LAMINATES;; SCANNING ELECTRON MICROSCOPY
URL	http://hdl.handle.net/2060/20120016494
보고서번호	NF1676L-15094
발행년도	2012
출처	NTRS (NASA Technical Report Server)
ABSTRACT	The intralaminar and interlaminar mode-I fracture-toughness of a unidirectional IM7/8552 graphite/epoxy composite were measured using compact tension (CT) and double cantilever beam (DCB) test specimens, respectively. Two starter crack geometries were considered for both the CT and DCB specimen configurations. In the first case, starter cracks were produced by 12.5 micron thick, Teflon film inserts. In the second case, considerably sharper starter cracks were produced by fatigue precracking. For each specimen configuration, use of the Teflon film starter cracks resulted in initially unstable crack growth and artificially high initiation fracture-toughness values. Conversely, specimens with fatigue precracks exhibited stable growth onset and lower initiation fracture toughness. For CT and DCB specimens with fatigue precracks, the intralaminar and interlaminar initiation fracture toughnesses were approximately equal. However, during propagation, the CT specimens exhibited more extensive fiber bridging, and rapidly increasing R-curve behavior as compared to the DCB specimens. Observations of initiation and propagation of intralaminar and interlaminar fracture, and the measurements of fracture toughness, were supported by fractographic analysis using scanning electron microscopy.