Dissertation
Dynamic fracture and fragmentation investigations of brittle polymers and composites
Doctor of Philosophy (Ph.D.), Drexel University
May 2019
DOI:
https://doi.org/10.17918/yr0n-6m76
Abstract
Dynamic fracture and fragmentation of brittle solids can result from the application of a single or repetitive impulsive load. As such, investigating the interactions between the geometric discontinuities of cracks with the surrounding material medium is imperative to further understand the effects of nonlinearities, material inhomogeneities, and length scale dependencies in failure. This thesis examines two types of brittle materials: nominally isotropic amorphous polymers and cermets, and (effectively) transversely isotropic cortical bone; as well as presents an improved experimental technique and a new piece of equipment used in failure investigations. Quasi-static and dynamic compressive behavior of ox bone and a commercial bone surrogate material has been examined, and the corresponding fragmentation characteristics quantified. A power law fit predicts both materials resulting fragmentation, however fragment sizes had clear links to the underlying osteon structure and direction of loading in the ox bone that was not present in the surrogate. To explore the efficacy of utilizing digital image correlation (DIC), a full-field kinematic mapping technique, in classical dynamic fracture investigations, the model material of PMMA has been investigated in mode-I (opening) crack initiation and formation. Higher order terms in the elastodynamic solution are added to account for inertial effects and built upon previous work exploring the relevant region of maintaining K-dominance. Based on the PMMA findings, the effect of inhomogeneous toughening on mode-I dynamic fracture conditions of a common composite matrix material, DGEBA, with various hardeners has been explored, and an improved speckling technique for DIC utilizing dot-on-demand colloidal inkjet printing is presented. Lastly, in order to explore the relevance of repetitive sub-critical impulsive loading on material fracture behavior, a unique impact fatigue device has been constructed and a case study investigating the effect of impact cycles and cobalt binder volume percent on the mode-I dynamic fracture behavior of tungsten carbide is presented.
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Details
- Title
- Dynamic fracture and fragmentation investigations of brittle polymers and composites
- Creators
- Steven James Pagano - DU
- Contributors
- Leslie Lamberson (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xi, 117 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Mechanical Engineering (and Mechanics) (1970-2026); Drexel University
- Other Identifier
- 9497; 991014632166804721