Förlagets beskrivning
OCLC Number: 55898550 Excerpt: ... 400 350 300 Propagation ( J / m2 ) 250 Initiation 200 GIc 150 100 50 0 0 10 20 30 40 50 60 Crack extension ( mm ) Figure 4. R-curve effect on a DCB test of a ( 0º ) CFRP laminate [ 7 ]. 24 Mode II There are four test specimens being considered for the measurement of interlaminar fracture toughnesses under Mode II loading [ 4, 5 ]: the end notched flexure specimen ( ENF ), the stabilized end notched flexure specimen ( SENF ), the four point end notched flexure specimen ( 4ENF ), and the end loaded split specimen ( ELS ). Although the ENF test specimen ( Figure 5 ) has received the most attention, it has problems associated with the unstable crack propagation for short crack lengths. One way to stabilize the ENF test is by feedback load control of the test machine [ 4, 11 ]. Applied load Insert Figure 5. ENF test specimen. According to Davies [ 4 ], the main problems associated with Mode II testing are the definition of the type of starter defect, the definition of crack initiation, the stability of the test, frictional effects on the crack faces and the data analysis. Furthermore, the Mode II fracture toughness is typically much higher and has more scatter than the Mode I fracture toughness [ 12 ]: for epoxy matrix composites the G / G IIC IC ratios typically exceed a value of 2. Observing the fracture surfaces that formed under Mode I and Mode II, O'Brien [ 12 ] concluded that under Mode II loading the fracture surface exhibits a rough fracture plane, including ' hackles ' ( Figure 6 ), whereas the Mode I fracture surface has a clean cleavage plane. O'Brien also concluded that for both composite laminates and structural elements, failure occurs at a location where Mode I accounts for at least half of the total G at failure, so Mode I and mixed-mode interlaminar fracture toughnesses are the most relevant for predicting delamination failure. 4
Liknande böcker
Recensioner
Den här boken har tyvärr inte några recensioner ännu. Om du redan läst boken, skriv en recension!
Recensera boken
Skriv en recension och dela dina åsikter med andra. Försök att fokusera på bokens innehåll. Läs våra instruktioner för mer information.
Numerical simulation of delamination growth in composite materials
Bokrecensioner » Numerical simulation of delamination growth in composite materials
|
|
 |
|
|
|
|
