Optimization of Origami Inspired Static and Active Mechanical Metamaterial

Origami-inspired materials provide effective solutions to control the mechanical properties of sandwich core structures, due to their outstanding structural features and due to the unique capacity of elastic deformation of its elements that are able to fold and unfold at different scales during the loading process. Both the geometrical features and the properties of the parent material that used to produce the origami structures are the most important factors required for tailoring the designed origami core with the target application. To eliminate the fracture and the abrupt stress change in the designed origami core elements, it is important to consider the parent material properties and behavior. There are two important challenges that should be considered in designing origami cores, the geometrical features of the origami tessellation and the material used to produce the origami unit cells and cores. Three dimensional origami cores can be fabricated by folding two dimensional flat sheets into three dimensional cores, or by pre-folding the origami features using a molding process. This research is devoted to investigate pre-folded origami cores made of polymeric materials for damping applications. Both passive and active properties of the designed unit cells were investigated in this research. Two different origami patterns were considered in the research, Miura and Ron-Resch-like origami structures. Different material blends were used to fabricate pre-folded origami features and correlate with the mechanical properties of the fabricated cores. Another way of preparing pre-folded origami cores is by using fused deposition modeling, in which different Ron-Resch-like cores with different geometrical parameters were designed and characterized for compression and impact load absorption. The designed origami cores were numerically simulated and compared with the experimental results. This motivated to include the viscoelastic behavior of the polymeric parent material at elevated temperature and simulate the cores’ unit cell using periodic boundary condition; the actual skeleton of the origami unit cell structure was represented in order to capture the mechanical behavior.Ph.D.2021-07-21 00:00:0

Sinteza i ispitivanje efekata rastvarača na UV spektre 1,3-bis-supstituisanih-5,5-dimetilhidantoina

A series of 1,3-bis-substituted-5,5-dimethylhydantoins was synthesized using the reaction of 5,5-dimethylhydantoin with the corresponding alkyl halide in the presence of trimethylamine as catalyst and sodium hydroxide, according to a modified literature procedure. The experimental investigation included modification of the synthetic procedure in terms of starting materials solvent, temperature, isolation techniques, as well as purification and identification of the products. The absorption spectra of the 1,3-bis-substituted-5,5-dimethylhydantoins were recorded in twelve solvents in the range 200–400 nm. The effects of the solvent polarity and hydrogen bonding on the absorption spectra were interpreted by means of linear solvation energy relationships using a general equation of the form ν = ν0 s¶* + aα + bβ and by two-parameter models presented by the equation ν = ν0 s¶* + aα, where ¶* is a measure of the solvent polarity/polarisability, α is the scale of the solvent hydrogen bond donor acidities and β is the scale of the solvent hydrogen bond acceptor basicities. The solvent and substituent effects on the electronic absorption spectra of the investigated hydantoins is discussed.U okviru rada je izvršena sinteza serije 1,3-bis-supstituisanih-5,5-dimetilhidantoina iz 5,5-dimetilhidantoina i odgovarajućeg alkilhalogenida u prisustvu trimetilamina kao katalizatora i natrijum-hidroksida, po modifikovanom postupku iz literature. Sintetizovani hidantoini su identifikovani na osnovu tačke topljenja, FTIR, 1H-NMR i UV spektroskopskih podataka. Apsorpcioni spektri 1,3-bis-supstituisanih-5,5-dimetilhidantoina su određeni u dvanaest rastvarača različite polarnosti u opsegu 200–400 nm. Uticaj polarnosti rastvarača kao i efekat vodonične veze proučavani su metodom linearne korelacije solvatacionih energija odnosno jednačinama oblika νmax = ν0 s¶*+aα + bβ i νmax = ν0 + s¶* + aα, u kojima je ν apsorpciona frekvencija ¶* mera efekata solvatacije vezana za polarnost rastvarača, α mera uspostavljanja vodonične veze sa proton-donorskim rastvarač ima, a β mera vodonične veze ostvarene sa protonakceptorskim rastvaračima. Rezultati prezentovani u ovom radu su veoma značajni za sagledavanje karakteristika 1,3-bis-supstituisanih- 5,5-dimetilhidantoina zbog njihove velike primene u kompozitnim materijalima kao vezujućih agenasa

Development and modeling of multi-phase polymeric origami inspired architecture by using pre-molded geometrical features

Using Origami folded cores in sandwich structures for lightweight applications has attracted attention in different engineering applications, especially in the applications where the stiffness to weight ratio is a critical design parameter. Recently, common sandwich cores such as honey-comb and foamed cores have been replaced with origami core panels due to their way of force redistribution and energy absorption; these unique characteristics give origami cores high stiffness to weight ratio and high bending and twisting resistance. This paper presents the results of experimental investigations of the effect of base material on the mechanical properties and the impact resistance of Miura–Origami sandwich cores; then, the experimental results are compared with FEA simulation results. The materials used in the study for the origami cores were polymer blends composed of polylactic acid (PLA) and thermoplastic polyurethane (TPU). PLA/TPU blend compositions are (100/0, 80/20, 65/35, 50/50, 20/80, and 0/100) as a weight percentage. The geometrical parameters of the unit cell, base material thickness, and the panel thickness were considered to be constants in this study. The study shows the behavior of the origami cores under impact test and the energy absorbed by the origami folded cores. It was found that 20/80 PLA/TPU blend demonstrated the highest specific energy absorption efficiency both in quasi-static compression and impact tests. Fractured Origami structures were observed to fail at folded edges (creases lines), while the facets exhibit rigid body rotations. The FEM simulation showed a consistency in the impact behavior of the origami cores, and the directional deformational of origami core units which explain the ability of the structure to redistribute the applied force and absorb energy. In this work the origami folded core features were molded directly from the blended material.The authors would like to acknowledge the following agencies for financial support: The Natural Science and Engineering Research Council (NSERC) of Canada, the Canada Research Chair Program, the Libyan Ministry of Higher Education and scientific research, Tripoli. And also the authors would like to extend their acknowledgements to Daniel Grozea, from Material Department for his technical support

Carbon nano fibers reinforced composites origami inspired mechanical metamaterials with passive and active properties

Core panels used for compression or impact damping are designed to dissipate energy and to reduce the transferred force and energy. They are designed to have high strain and deformation with low density. The geometrical configuration of such cores plays a significant role in redistributing the applied forces to dampen the compression and impact energy. Origami structures are renowned for affording large macroscopic deformation which can be employed for force redistribution and energy damping. The material selection for the fabrication of origami structures affects the core capacity to withstand compression and impact loads. Polymers are characterized by their high compression and impact resistance; the drawback of polymers is the low stiffness and elastic moduli compared with metallic materials. This work is focused on the study of the effect of Carbon Nano Fibers (CNF) on the global mechanical properties of the origami panel cores made of polymeric blends. The base matrix materials used were Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) blends, and the percentages of the PLA/TPU were 100/0, 20/80, 65/35, 50/50, 20/80, and 0/100 as a percentage of weight. The weight percentages of CNF added to the polymeric blends were 1%, 3%, and 5%. This paper deals with the fabrication process of the polymeric reinforced blends and the origami cores, in order to predict the best fabrication conditions. The dynamic scanning calorimetry and the dynamic mechanical analyzer were used to test the reinforced blended base material for thermomechanical and viscoelastic properties. The origami core samples were fabricated using per-molded geometrical features and then tested for compression and impact properties. The results of the study were compared with previous published results which showed that there is considerable enhancement in the mechanical properties of the origami cores compared with the pure blended polymeric origami cores. The active properties of the origami unit cell made of composite polymers containing a low percentage of CNF were also investigated in this study, in which the shape memory effect test conducted on the origami unit cell.The authors would like to acknowledge the following agencies for financial support: The Natural Science and Engineering Research Council (NSERC) of Canada, the Canada Research Chair Program, the Libyan Ministry of Higher Education and scientific research, Tripoli

Synthesis and investigation of solvent effects on the ultraviolet absorption spectra of 1,3-bis-substituted-5,5-dimethylhydantoins

A series of 1,3-bis-substituted-5,5-dimethylhydantoins was synthesized using the reaction of 5,5-dimethylhydantoin with the corresponding alkyl halide in the presence of trimethylamine as catalyst and sodium hydroxide, according to a modified literature procedure. The experimental investigation included modification of the synthetic procedure in terms of starting materials, solvent, temperature, isolation techniques, as well as purification and identification of the products. The absorption spectra of the 1,3-bis-substituted-5,5-dimethylhydantoins were recorded in twelve solvents in the range 200400 nm. The effects of the solvent polarity and hydrogen bonding on the absorption spectra were interpreted by means of linear solvation energy relationships using a general equation of the form n = n0 + sp* + aa + bb and by two-parameter models presented by the equation n = n0 + sp* + aa, where p* is a measure of the solvent polarity/polarisability, a is the scale of the solvent hydrogen bond donor acidities and b is the scale of the solvent hydrogen bond acceptor basicities. The solvent and substituent effects on the electronic absorption spectra of the investigated hydantoins is discussed

Original scientific paper

Synthesis and investigation of solvent effects on the ultraviolet absorption spectra of 1,3-bis-substituted-5,5-dimethylhydantoin