Preparation of Benzoxazine Monomers and Prepolymers from Continuous Reactor: Effects of Molecular Architecture on Properties

Despite the modularity in molecular design and high-performance properties of benzoxazine thermoset chemistries, there are two primary shortcomings of benzoxazine marketability. Firstly, multifunctional benzoxazines are unfavorable for processing as they are glassy solids at ambient temperature. Secondly, benzoxazine chemistries are commercially synthesized using batch reactors, which are energy intensive and require the use of environmentally unfavorable solvents. The purpose of the work herein is to address these shortcomings, which include: 1.) interrelationships between molecular architectures of synthesized monofunctional benzoxazine monomers and their ambient temperature physical states (i.e. liquid or solid) using molecular dynamics simulations and experimental comparisons, 2.) continuous high-shear reactor designs to synthesize high-purity benzoxazine monomers and prepolymers, and 3.) correlations between the molecular architecture and percent loading of fluorinated monofunctional benzoxazine reactive diluent isomers on the thermal and bulk mechanical properties of BPABOX networks. In Chapters I and II, research motives and all experimental and characterization methods are provided. Chapter III of this work involved synthesizing and simulating a library of monofunctional benzoxazine monomers varied by substituent placement and identity. Annealing simulations demonstrated a discontinuity that provided a qualitative prediction of the physical state of benzoxazine monomers. Ab initio calculations demonstrated that electron rich domains align with electron poor domains providing localized order within a monomeric system and a solid physical state. In Chapter IV, a novel continuous high-shear reactor design, CHSR, for the synthesis of benzoxazine monomers and prepolymers is provided. Validated by 1H NMR, the CHSR demonstrated throughputs that are 6-40x faster with improved target monomer conformation as compared to current reactor technologies. Proton NMR comparisons of monomers synthesized and purified from a batch reactor versus unpurified monomers from the CHSR demonstrated that the CHSR yields a high purity product eliminating the need for post-processing purification. Chapter V of this work involved the preparation of benzoxazine alloys to elucidate the effects of molecular architecture and percent loading of fluorinated reactive diluent isomers on the BPABOX bulk matrix properties. Contrastingly, 49 wt.% of diluent was determined as the critical loading for an isomer effect on the cured network properties. Despite the increasing molecular weight between crosslinks with increasing diluent loading, plasticization was prevented up to 30 wt.% diluent. The added fluorine content afforded increased secondary interactions that could provide added energy dissipation modes to toughen the inherently brittle neat BPABOX network as demonstrated via dynamic mechanical analyses and uniaxial compression results

Development of a metamaterial for use in American football head protection

American football athletes are exposed to a high number of head impacts of varying severity throughout the course of regular play. The sport has a high rate of concussions, despite mitigating strategies, including protective helmets, when compared to other contact sports. Current helmets commonly use elastomeric foams as the principal energy absorption mechanism to protect players from injury. However, these foams have limited performance ranges due to their mechanical properties. Therefore for better player protection, a novel material was required. Novel materials and structure combinations presented the ability to leverage material properties that had the potential to expand the performance range of a helmet liner. This study investigated a metamaterial based on stacked layers of the Miura Ori folding pattern, which offered both improved performance and ample scope for optimisation. The Taguchi method was used to design a series of samples manufactured from thermoplastic polyurethane, tested using a series of validated impacts. Data from these impacts were used to refine the geometry, using statistical processes, such that measured accelerations and injury metrics were minimised. The metamaterial's final design was then tested as part of a helmet to establish the improvement in performance offered over the original foam liner. The selected geometry reduced the risk of a player sustaining mild brain injuries while offering comparable protection against catastrophic injuries when impacted. This risk reduction not only reduces the number of injuries that could be expected over players’ careers but also has the potential to reduce the probability of players developing neurogenerative conditions later in their lives

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version

Proceedings / 6th International Symposium of Industrial Engineering - SIE 2015, 24th-25th September, 2015, Belgrade

editors Vesna Spasojević-Brkić, Mirjana Misita, Dragan D. Milanovi

Proceedings / 6th International Symposium of Industrial Engineering - SIE 2015, 24th-25th September, 2015, Belgrade

editors Vesna Spasojević-Brkić, Mirjana Misita, Dragan D. Milanovi

Numerical analysis of fatigue crack growth in welded joints with multiple defects

In the case of welded steel structures (such as pressure equipment), welded joints are often critical location for stress concentrations, due to different mechanical properties and chemical composition compared to the parent material, and due to changes in geometry. In addition, the presence of imperfections (defects) in welded joints can contribute to the increase in local stress, resulting in crack initiation. Recently, standards that are related to acceptable dimensions of various types of defects in welded joints started taking fatigue loading into account as well. For the purpose of this research, a 3D numerical model was made, of a welded joint with different types of defects (linear misalignment and a crack in the weld metal), based on the previous work, which involved static loading of the same specimen. In this case, fatigue was taken into account, and the simulation was performed using ABAQUS software, as well as Morfeo, an add-on used for determining the fatigue behaviour of structures via XFEM (extended finite element method). The welded joint was made using steel P460NL1 as the parent material, and EPP2NiMo2 wire was used for the weld metal. An additional model was made, whose defects included a crack and an overhang. Fatigue crack growth analysis was performed for this model as well, and the results for stress intensity factors and stress/strain distribution were compared in order to obtain information about how different defects can affect the integrity of a welded joint

The influence of oxide deposits on the remaining life and integrity of pressure vessels equipment

In this paper is presented the principle of application of fracture mechanics parameters in determining the integrity of rotary equipment. The behavior of rotary equipment depends on presence of cracks and basically determines the integrity and life of such equipment. The locations of stress concentration (i.e. radius changes) represent a particular problem in rotary equipment, and they are the most suitable places for the occurrence of microcracks i.e. cracks due to fatigue load. This problem is most common in the shaft of relatively large dimensions, for example, turbine shafts in hydropower plants made of high-strength carbon steel with relatively low fracture toughness, and relatively low resistance to crack formation and growth. Having in mind that rotary equipment represents the great risk in the exploitation, whose occasional failures often had severe consequences, it is necessary detail study of their integrity. For this purpose, it is necessary application of parameters of linear-elastic fracture mechanics, such as stress intensity factor, which range defines the rate of crack growth (Parisian law), and its critical value (fracture toughness) determines the critical crack length. The procedures for determining the critical crack length will be described using the fracture mechanics parameters

Multibody dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: Formulations and Numerical Methods, Efficient Methods and Real-Time Applications, Flexible Multibody Dynamics, Contact Dynamics and Constraints, Multiphysics and Coupled Problems, Control and Optimization, Software Development and Computer Technology, Aerospace and Maritime Applications, Biomechanics, Railroad Vehicle Dynamics, Road Vehicle Dynamics, Robotics, Benchmark Problems. The conference is organized by the Department of Mechanical Engineering of the Universitat Politècnica de Catalunya (UPC) in Barcelona. The organizers would like to thank the authors for submitting their contributions, the keynote lecturers for accepting the invitation and for the quality of their talks, the awards and scientific committees for their support to the organization of the conference, and finally the topic organizers for reviewing all extended abstracts and selecting the awards nominees.Postprint (published version

Using the fracture mechanics parameters in assessment of integrity of rotary equipment

In this paper is presented the principle of application of fracture mechanics parameters in determining the integrity of rotary equipment. The behavior of rotary equipment depends on presence of cracks and basically determines the integrity and life of such equipment. The locations of stress concentration (i.e. radius changes) represent a particular problem in rotary equipment, and they are the most suitable places for the occurrence of microcracks i.e. cracks due to fatigue load. This problem is most common in the shaft of relatively large dimensions, for example, turbine shafts in hydropower plants made of high-strength carbon steel with relatively low fracture toughness, and relatively low resistance to crack formation and growth. Having in mind that rotary equipment represents the great risk in the exploitation, whose occasional failures often had severe consequences, it is necessary detail study of their integrity. For this purpose, it is necessary application of parameters of linear-elastic fracture mechanics, such as stress intensity factor, which range defines the rate of crack growth (Parisian law), and its critical value (fracture toughness) determines the critical crack length. The procedures for determining the critical crack length will be described using the fracture mechanics parameters