Carbon nanotubes (CNT) have unparalleled mechanical properties, spanning several orders of magnitude over both length and time scales. Computational and experimental results vary greatly, partly due to the multitude of variables. Coupling physics-based molecular dynamics (MD) with informatics methodologies is proposed to navigate the large problem space. The adaptive intermolecular reactive empirical bond order (AIREBO) is used to model short range, long range and torsional interactions. A powerful approach that has not been used to study CNT mechanical properties is the derivation of descriptors and quantitative structure property relationships (QSPRs). For the study of defected single-walled CNTs (SWCNT), two descriptors were identified as critical: the density of non-sp2 hybridized carbons and the density of methyl groups functionalizing the surface. It is believed that both of these descriptors can be experimentally measured, paving the way for closed-loop computational-experimental development. Informatics can facilitate discovery of hidden knowledge. Further evaluation of the critical descriptors selected for Poisson’s ratio lead to the discovery that Poisson’s ratio has strain-varying nonlinear elastic behavior. CNT effectiveness in composites is based both on intrinsic mechanical properties and interfacial load transfer. In double-walled CNTs, inter-wall bonds are surface defects that decrease the intrinsic properties but also improve load transfer. QSPRs can be used to model these inverse effects and pinpoint the optimal amount of inter-wall bonds.

Improving the mechanical properties of a clayey soil is one of the best options to avoid future structural failures in buildings and is cheaper than replacing all the material. Therefore, this article proposes the use of recycled glass and fan shells as reinforcement materials. This article presents an experimental study to evaluate the mechanical properties of a pure and mixed soil. The clay soil was mixed with 7% of glass (PV) and with 3%, 6%, 10%, 12% and 15% of Fan Shells (PCA) duly crushed and passed through sieve #100. Tests of sieve granulometry, sedimentation granulometry, Atterberg limits, modified proctor and drained consolidated direct cut were performed. This allowed comparing all the data obtained and defining the optimal percentage of the mixture in which the clay improves its mechanical properties. According to the tests carried out, the proportion that has 7% glass and 6% Fan Shells has better results because there is an improvement in its dry density from 1,784 g / cm3 to 1,847 g / cm3, its moisture content increases from 9.4% to 12.1%. In addition, its friction angle improves from 28.9 °to 32 °and cohesion from 0.05 kg / cm2 to 0.1 kg / cm2. These results verify that the properties of the clay soil are improved.

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The southern pine species group is the main softwood resource used in the U.S, and the majority of southern pine is used in lumber production. The use of lumber in structural purpose requires feasible strength and stiffness grading method ensuring characteristics allowable stress values. The stiffness and strength of most of southern pine lumber is assessed using visual grading system. The objective of this study was to evaluate a production weighted sample of 2 × 4, 2 × 6, 2 × 8, and 2 × 10 No. 2 grade southern pine lumber collected across its geographic range. The results of this research show a snapshot of the material commercially sold in the southern U.S. region. Over one third of the specimens contained pith, and had an average mean value of 4.6 for number of rings per inch (RPI) and 43.8% for latewood (LW). The overall specific gravity (SG), modulus of elasticity (MOE) and modulus of rupture (MOR) were 0.54, 10.1 GPa, and 41.7 MPa, respectively. The allowable design bending strength (Fb) for 2 × 4, 2 × 6, 2 × 8, and 2 × 10 was 11.2, 9.2, 8.1, and 7.1 MPa, respectively. Specimens containing no pith, RPI higher or equal then 4.0, and LW higher or equal then 33.0% were greater in MOE and MOR. The effect of grading controlling characteristics of the material was also studied. The presence of knots had the most significant impact on mechanical properties. Specimens with wane and shake had greater SG, MOE, MOR, Fb values than specimens with others grading controlling characteristics. The mean values found for RPI, LW, and SG met the requirements recommended for southern pine No. 2 lumber. The MOE and Fb values found therein met the previous and the new allowable design value. The results of this research can be used to identify and to select the best variables to improve the prediction of bending properties of visually graded lumber.

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Yes / The effects of 0·5 wt-%Mo addition on the processing, microstructure, and strength of PM Fe–3·5Mn–0·7C steel are described. Water atomised and sponge irons, Astaloy 1·5Mo, milled ferromanganese, and graphite were the starting powders. During sintering in 75H2 /25N2 or pure hydrogen the dewpoint was controlled and monitored; in particular the effects of improving it from -35 to -60°C were investigated. Faster heating rates (20 K min-1), sufficient gas flowrates, milling the ferro alloy under nitrogen, a low dewpoint (<-60°C), and a getter powder can all contribute to the reduction or prevention of oxidation of the manganese, in particular formation of oxide networks in the sintered steels. For 600 MPa compaction pressure densities up to 7·1 g cm-3 were obtained; these were not significantly affected by sintering at temperatures up to 1180°C. The sintered microstructures were sensitively dependent on the cooling rate. Irrespective of the presence of Mo, slow furnace cooling at 4 K min-1 resulted in mainly pearlitic structures with some ferrite and coarse bainite, whereas fast cooling at 40 K min-1 produced martensite and some retained austenite, very fine pearlite, bainite, and some ferrite. Young's modulus, determined by tensile and ultrasonic tests, was in the range 110–155 GPa. Sintering with -60°C dewpoint resulted in tensile and transverse rupture strengths of 420 and 860 MPa for the Mn steel, rising to 530 and1130 MPa as a result of the Mo addition. This contrasts with strength decreases observed when processing included use of high oxygen containing ferromanganese and sintering with -35°C dewpoint.

Yes / The fracture resistance of polymethylmethacrylate (PMMA) as the most popular denture base material is not satisfactory. Different factors can be involved in denture fracture. Among them, flexural fatigue and impact are the most common failure mechanisms of an acrylic denture base. It has been shown that there is a correlation between the static strength and fatigue life of composite resins. Therefore, the transverse strength of the denture base materials can be an important indicator of their service life. In order to improve the fracture resistance of PMMA, extensive studies have been carried out; however, only a few promising results were achieved, which are limited to some mechanical properties of PMMA at the cost of other properties. This study aimed at optimizing the packing and processing condition of heat-cured PMMA as a denture base resin in order to improve its biaxial flexural strength (BFS). The results showed that the plain type of resin with a powder/monomer ratio of 2.5:1 or less, packed conventionally and cured in a water bath for 2 h at 95 °C provides the highest BFS. Also, it was found that the performance of the dry heat processor is inconsistent with the number of flasks being loaded.

Yes / A multi-element constitutive model for a lactide-based shape memory polymer has been developed that represents loading to large tensile deformations, stress relaxation and stress recovery at 60, 65 and 70°C. The model consists of parallel Maxwell arms each comprising neo-Hookean and Eyring elements. Guiu-Pratt analysis of the stress relaxation curves yields Eyring parameters. When these parameters are used to define the Eyring process in a single Maxwell arm, the resulting model yields at too low a stress, but gives good predictions for longer times. Stress dip tests show a very stiff response on unloading by a small strain decrement. This would create an unrealistically high stress on loading to large strain if it were modelled by an elastic element. Instead it is modelled by an Eyring process operating via a flow rule that introduces strain hardening after yield. When this process is incorporated into a second parallel Maxwell arm, there results a model that fully represents both stress relaxation and stress dip tests at 60°C. At higher temperatures a third arm is required for valid predictions.