| dc.description.abstract | Mixed mode loading often has a significant effect on fracture behaviour in components.
Cracks is in many cases the reason for failure or fracture of a component. All
of the mechanisms of cracks and fracture behaviour are still not completely known.
This also applies for the three dimensional loading case of mixed mode I/II/III.
This thesis will therefore study the existing theory on two dimensional, and three
dimensional mixed mode loading. Mixed mode I/II/III brittle fracture behaviour of
polymethyl methacrylate, PMMA, will be studied experimentally and theoretically,
using pre-cracked CTS specimens. This specimens contains pre-cracks and will be
subjected to different mixed mode loading conditions, ranging from pure mode I to
pure mode II and pure mode III. During this thesis, a mixed mode I/II/III loading
device were designed and used for the experimental procedure. Experiments were
conducted on all twenty five combinations of the loading device. The presented
mixed mode loading device allowed mixed mode I/II/III loading combinations in
steps of 22:5, for in and out of plane rotations. After the conducted experiments,
fracture loads were obtained. In-plane crack initiation angles and out of plane crack
initiation angles were measured for all of the fractured specimens. These experimentally
obtained results were then compared with predictions of various fracture
criteria. Maximum tangential stress criterion, MTS, generalized maximum tangential
stress criterion, GMTS, and the criterion by Richard were used for numerical
predictions in this thesis. Numerical analysis were conducted by obtaining results
from three-dimensional finite element simulations in Abaqus, and applying them in
different fracture criteria. The criteria showed a good relation with experimentally
obtained angles. | |
