A study on cork-based plastic composite material

Thesis (Mech. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 115-116).Sandwich panels are mainly used in construction for lightweight structures since their concept is appropriate due to extremely high in-plane and flexural stiffness to weight ratios. However, low structural freedom and high environmental burdens of core material in sandwich panels such as fiberglass, and chemically synthesized foams have retarded a wide use in various areas. Recently it has been suggested that the better performance and economic, environmental benefits could be possibly achieved by using hybrid sandwich panels comprising non-traditional pairs of materials for sandwich panels. Therefore, in this paper, a cork-based plastic composite material has been proposed as a new core material and the possibility for substituting existing core materials have been explored by investigation on its mechanical properties, economic benefit, and environmental impact. Several mechanical testing were carried out on the cork composite and Glass Fiber Reinforced Plastic (GFRP) to determine the mechanical properties and compare their relative performances. By conducting property-limited design cases with the obtained mechanical properties, how they will perform in light, stiff panel application was investigated. Economic analysis was demonstrated with a table top application by using rigidity equality condition. Finally, Eco-impact of the cork composite was investigated by conducting Life Cycle Assessment. The result proved that the cork composite is competitive with other core materials.by Sungmin Kim.Mech.E

Resilience of some man-made fibres

The first part of this research is concerned with the standardisation of a test method to determine the resilience of fibres. The influence of both time and maximum pressure is studied and the loading and unloading cycle is standardised to measure resilience with three maximum pressures (0.01, 0.10 and 1.0 p.s.i.) in the minimum time. The effects of specimen preparation and specimen dimensions (areas and thicknesses) and also the effects of presser foot areas and shapes(plane or hemispherical compressing surface) on measured resilience are investigated. The second part of this work is devoted to investigating those intrinsic fibre properties, which may affect resilience. Six fibre properties, namely, staple length, diameter (denier), crimp characteristics (i.e. percent crimp, uncrimping force, uncrimping energy), inter-fibre friction, tensile elastic recovery and initial modulus are studied. Crimp has the highest influence on resilience whereas fibre friction and diameter indicate comparatively less effect. The staple length shows no significant correlation with resilience and both elastic recovery and initial modulus are also not correlated with resilience. These investigations were carried out on Acrilan, Terylene, and Tricel fibre. The possibility of expressing the thickness-pressure relationship by an equation is considered. The results fit an exponential equation of the form: T = a Pb where 'T' is thickness of the specimen, 'P' is pressure and 'a' and 'b' are constants. The effect of both humidity and temperature on the resilience of fibres is investigated. The resilience decreases as the relative humidity increases. On the other hand there is an increase in resilience with the increase in temperature. Comparison is made between Acrilan, Terylene and Tricel fibres. The influence of surface properties (i.e. amount of finish) of Acrilan studied in relation to the resilience of fibres

Preparation and characterization of cellulose nanoparticles and their application in biopolymeric nanocomposites

Regenerated cellulose nanoparticles (RCNs) including both elongated fiber and spherical structures were prepared from microcrystalline cellulose (MCC) and cotton using 1-butyl-3-methylimidazolium chloride followed by high-pressure homogenization. The RCN has a two-step pyrolysis, different from raw MCC and cotton that had a one-step process. The crystalline structure of RCNs was cellulose II in contrast to the cellulose I form of the starting materials. Also, the RCNs have decreased crystallinity and crystallite size. The elongated RCNs produced from cotton and MCC had average lengths of 123 ± 34 and 112 ± 42 nm, and mean widths of 12 ± 5 and 12 ± 3 nm, respectively. The average diameter of spherical RCNs from MCC was 118 ± 32 nm. Cellulose nanocrystals and cellulose nanofibers with I and II crystalline allomorphs (designated as CNC I, CNC II, CNF I, and CNF II) were isolated from bleached wood fibers by alkaline pretreatment and acid hydrolysis. The effects of concentration, particle size, surface charge, and crystal structure on the lyophilization-induced self-assembly of cellulose particles in aqueous suspensions were studied. Within the concentration range of 0.5 to 1.0 wt %, cellulose particles self-organized into lamellar structured foam composed of aligned membrane layers with widths between 0.5 and 3 ì m. At 0.05 wt %, CNC I, CNF I, CNC II, and CNF II self-assembled into oriented ultrafine fibers with mean diameters of 0.57, 1.02, 1.50, and 1.00 ì m, respectively. Cellulose nanoparticle (CNP) reinforced Polyvinyl alcohol-borax (PB) hydrogels were prepared through a facile approach in an aqueous medium. The obtained stiff, high-water-capacity (~96%), low-density (~1.1g/cm3), translucence hydrogels exhibited birefringence textures. These free-standing, high elasticity and mouldable hydrogels also exhibited self-recovery under continuous step strain and thermo-reversibility under temperature sweep. The rheological tests and compression measurements confirmed the incorporation of well-dispersed CNPs to PB system significantly enhanced the compressive strength, viscoelasticity and stiffness of the hydrogels. Highly-crystalline CNPs not only tangled with PVA chains though numerous hydrogen bonds, but formed chemically crosslinked complexes with borax ions as well, thus acting as multifunctional crosslinking agents and nanofillers to physically and chemically bridge the 3D network hydrogels

Fibre properties affecting the softness of wool and other keratins

The emerging market for next-to-skin knitwear requires wool to satisfy the consumer’s tactile requirements for softness. The role of the fibre’s surface and physical properties on fibre and fabric softness was examined. The fibre’s cuticle properties were found to have a greater influence on softness than the fibre’s mechanical properties

Lightweight structural design of UAV wing through the use of coreless composite materials employing novel construction techniques.

Master of Science in Mechanical Engineering. University of KwaZulu-Natal, Pietermaritzburg, 2017.A new structural layout was designed for an existing UAV wing with the aims of lightening the wing by eliminating the use of cored composite construction and reducing the manufacturing time of the wing by making use of waterjet-cut internal frames while satisfying strength and stiffness requirements. Two layouts, a traditional metal wing layout and a tri-directional rib lattice layout, were selected for consideration based on the literature surveyed. In order to present a valid comparison with the previous wing design the same composite materials were used in the design of the new wing layout and material tests were performed according to ASTM testing standards to obtain the mechanical properties of these materials. Load cases for the wing in flight were calculated according to FAR-23 standards and the loads on the wing were found using XFLR5 vortex-lattice methods. An empirical, spreadsheet-based initial sizing tool was developed to obtain initial layups for an iterative FEA-based optimisation process that employed the SolidWorks Simulation Premium software package and made use of the Tsai-Wu composite material failure criterion and empirical buckling equations. The iterative optimisation resulted in the traditional metal wing layout being selected and predicted a weight saving of 14% over the original wing design. A full scale prototype wing was constructed in the CSIR UAS Laboratory using wet layup techniques and laser cut internal frames as it was found that the waterjet cutting of thin composite frames was not practical as a result of the high working pressure of the waterjet cutter. The prototype wing showed an actual weight saving of 14% but took considerably longer to manufacture due to the necessity of constructing specialised jigs to aid in the bonding and alignment of the internal frames. The prototype wing was tested using a custom set-up whiffle tree rig up to its maximum limit load of 4.9 g and showed an average of 4% error between measured and predicted deflections thereby validating the FEA models. It was concluded that a UAV wing can be significantly lightened through a coreless structural design, but at the expense of an increase in construction time. It is hoped that this study will contribute towards a changed design philosophy in an industry where cored construction is the norm. It is recommended that the methods developed during this project be applied to the rest of the aircraft components in order to obtain a lighter overall structure

Biopolymers from Natural Resources

This work covers all aspects related to the obtainment, production, design, and processing of biopolymers obtained from natural resources. Moreover, it studies characteristics related to the improvement of their performance to increase their potential application at an industrial level, in line with the concept of a global circular economy. Thus, this work firstly classifies biopolymers obtained from natural resources (e.g., biobased building blocks and biopolymers extracted directly from plants and biomass), and then summarizes several cutting-edge research works focused on enhancing the performance of biopolymers from natural resources to extend their application in the industrial sector, and contribute to the transition to more sustainable plastics

Clusters, Waves, and Force Chains in Fire-Ant Collectives: Emergent Behavior in Out-of-Equilibrium Particulate Systems

Unlike other out-of-equilibrium systems, active matter is held far from equilibrium by energy input at the single particle level. The field includes a wide range of systems, but the most familiar examples, including flocks of birds and schools of fish, are biological. Despite the prevalence of biological systems, most of the important experimental work over the last two decades has examined synthetic systems with relatively simple particle interactions that closely approximate theoretical models. In this thesis, we examine fire ants, a biological system with complicated social interactions, and compare their behavior to expectations from active matter theory. We find surprising evidence of two hallmark aspects in active matter, collective-motion and motility-induced phase separation. Then, we demonstrate that the ants propagate a new type of nonlinear solitary wave in 2D columns, in which the ants activate and deactivate as the wave passes them, indicating the importance of time-dependent activity in future models of active matter. We also compare 3D columns of ants to columns of fluids and passive grains. Our results show that activity is not enough to fully wash out the granular nature of the ants. Finally, we turn to a synthetic system, vibrated polar disks, to examine the nature of the collective-motion phase transition in finite systems and find that the phase transition is qualitatively different than in the infinite-size limit. We argue that, in contrast to equilibrium systems, finite size effects are likely important in predicting the behavior of most practical active matter systems. Altogether, our work shows that the universal predictions of active matter theory are robust to the nature of particle interactions and proposes simple new directions for future theory to encompass more complicated active matter systems.Ph.D

Wood Science for Conservation of Cultural Heritage – Braga 2008

COST Action IE0601 "Wood Science for Conservation of Cultural Heritage" (www.woodculther.org) aims to improve the conservation of European wooden cultural heritage objects, by fostering research and interaction between researchers in various fields of wood science, conservators of wooden artworks, scientists from related fields. These proceedings contain the papers presented in the 2nd International Conference held in Braga (Portugal) 5-7/11/2008, dealing with themes such as material properties, biological degradation, characterization and measurement techniques, conservation, structures. This conference was patronized by the European Society for Wood Mechanics (ESWM), an informal body promoting wood mechanics in Europe by regular organisation of meetings through running COST Actions