Three-dimensional quadratic failure criteria for thick composites using the Direct Micromechanics Method
2007 (English)In: American Society for Composites - 22nd Technical Conference of the American Society for Composites 2007 - Composites: Enabling a New Era in Civil Aviation, 2007, 612-631 p.Conference paper (Refereed)
Majority of failure criteria currently used for unidirectional fiber composites assume a state of plane stress and are therefore only applicable to thin laminates. As fiber composites are also used in thick structures with significant out of plane stresses, new failure criteria are required. The Direct Micromechanics Method, DMM, is used to determine the exact failure envelope of a unidirectional graphite/epoxy composite. A hexagonal unit cell of the composite is modeled using finite elements. Assuming that the failure criteria for the fiber and matrix materials and for the interface are known, the exact failure envelope is constructed from several three-dimensional stress states that correspond to failure initiation in the composite. These 3D failure stress states are then used to develop five three-dimensional phenomenological failure criteria: Maximum Stress, Maximum Strain, Quadratic Stress, Quadratic Strain and Optimized Quadratic Failure Criteria. These criteria are compared with the DMM failure envelope and with available 2D failure criteria. It is observed that the 3D Quadratic Stress and Strain Failure Criteria may be open, meaning that they predict infinite strength in some directions. However, they can be made closed in combination with the Maximum Stress or the Maximum Strain Failure Criterion. It is observed that a combination of aforementioned 3D failure criteria make failure prediction in thick composites more accurate and reliable and is comparable to that of Tsai-Wu criterion for thin composites under plane stress conditions. The proposed Optimized Quadratic Failure Criteria is always closed and is more reliable than all other 3D criteria.
Place, publisher, year, edition, pages
2007. 612-631 p.
Civil aviation, Interface states, Interfaces (materials), Optimization, Textiles, Three dimensional, Three dimensional computer graphics
IdentifiersURN: urn:nbn:se:kth:diva-154672ScopusID: 2-s2.0-84867808627ISBN: 978-160423966-9OAI: oai:DiVA.org:kth-154672DiVA: diva2:758519
22nd Technical Conference of the American Society for Composites 2007 - Composites: Enabling a New Era in Civil Aviation, 17 September 2007 through 19 September 2007, Seattle, WA, United States
QC 201410272014-10-272014-10-272014-10-27Bibliographically approved