Engineering

Crack closure

Materials science

Displacement (psychology)

Bending

Compact tension specimen

Ultimate tensile strength

Operating system

Joint (building)

Crack growth resistance curve

Computer science

Geology

Paleontology

Type (biology)

Finite element method

Crack tip opening displacement

Digital image correlation

Psychology

Mixed mode

Psychotherapist

Fracture toughness

Composite material

Structural engineering

Fracture (geology)

Tension (geology)

Strain energy release rate

Mode (computer interface)

Fracture mechanics

Composite Structures

Mode II fracture toughness tests for a type of double-lap joint referred to as the doubly end notched tension (DENT) tests were validated by experimental and numerical approaches. Crack growth behavior of two cracks was simultaneously observed during fracture toughness tests and analyzed by the digital image correlation (DIC) method. As one of the two cracks propagated first and the other followed, finite element (FE) analyses were carried out to clarify the mechanisms. The results of FE analyses showed that mode II energy release rate at the extended crack tip increased at the beginning of crack growth, and subsequently decreased under constant displacement condition. An opposite trend was found at the other crack tip. One cause of this phenomenon was due to local bending of the specimen. The effects of the geometry of specimens were also discussed. The FE analyses also revealed that the ratio of middle layer thickness to the outer layers thickness significantly affects the crack growth behavior in the DENT specimens.

Experimental and analytical validation of mode II fracture toughness tests for a type of double-lap joint