First Principle Study on Mg2X (X = Si, Ge, Sn) Intermetallics by Bi Micro-Alloying

Being a positive candidate reinforcement material for laminar composites, the Mg2X (X = Si, Ge, Sn) based intermetallics have attracted much attention. The elastic properties, anisotropy, and electronic properties of intermetallic compounds with Bi-doped Mg2X (X = Si, Ge, Sn) are calculated by the first principles method. Results show that the lattice parameters of Mg2X are smaller than those of Bi-doped Mg2X. The element Bi preferentially occupies the position of the X (X = Si, Ge, Sn) atom than other positions. Mg2X (X = Si, Ge, Sn), Mg63X32Bi, Mg64X31Bi, Mg64Ge32Bi, and Mg64Sn32Bi are mechanically stable, while Mg64Si32Bi indicates that it cannot exist stably. The doping of alloying element Bi reduces the shear deformation resistance of the Mg2X (X = Si, Ge, Sn) alloy. The pure and Bi-doped Mg2X (X = Si, Ge, Sn) exhibits elastic and anisotropic characteristics. The contribution of the Bi orbitals of Mg63X32Bi, Mg64X31Bi, and Mg63X32Bi are different, resulting in different hybridization effects in three types of Bi-doped Mg2X.

Preparation and Study of Flexural Strength and Impact Strength for Hybrid Composite Materials used in Structural Applications

Many of the polymeric materials used for structural purposes have weak mechanical properties, these characteristics can therefore be improved by preparing a hybrid laminar composite. In this work use melting mixing method using screw extruder to prepare sheets of polymer blends and nanocomposites based on polymer blends, and using a hot hydraulic press machine to prepared hybrid laminates composites. Two groups of hybrid laminar composites were prepared, the first group is consist of [((94%PP: 5%PMMA: 1 %( PP-g-MA)): 0.3% ZrO2): 6%KF and 8%KF] and the second group is [((94%PP: 5%UHMWPE: 1 %( PP-g-MA)): 0.3% ZrO2): 6%KF and 8%KF]. The results illustrated the impact strength and fracture toughness are increase with increased weight percentage of Kevlar fiber in for both groups of laminar composites and the highest values for two groups are (58.1, 54.95 KJ/M2) and (8.4, 9.16 MPa√m) respectively, any that, at the rate of increment reached to (120.4%, 107%) and (52.7%, 66.5%) respectively, compared with the neat PP. Moreover, the flexural strength values of the first group samples of hybrid laminar composite remained constant, when added kevlar fiber to nanocomposite. While, the flexural strength values of the second group samples of hybrid laminar composite increase with increase the ratio of kevlar fiber in composite to reach the maximum values (92 MPa) at 8% wt. of kevlar fiber, any, at the rate of increment reached to 39.4% compared with the neat PP. As well as, the results shown that the flexural properties and fracture toughness of the second group samples higher than they are for the first group samples.

DIAGRAMS FOR STRESS AND DEFLECTION PREDICTION IN CROSS-LAMINATED TIMBER (CLT) PANELS WITH NON-CLASSICAL BOUNDARY CONDITIONS

Invention of cross-laminated timber (CLT) was a big milestone for building with wood. Due tonovelty of CLT and timber’s complex mechanical behavior, the existing design codes cover onlyrectangular CLT panels, simply supported along 2 parallel or all 4 edges, making numerical methodsnecessary in other cases. This paper presents a practical engineering tool for stress and deflectionprediction of CLT panels with non-classical boundary conditions, based on the software for thecomputational analysis of laminar composites, previously developed by the authors. Diagramsapplicable in engineering practice are developed for some common cases. The presentedmethodology could be a basis for more detailed design handbooks and guidelines for various layoutsof CLT panels and different types of loadings.

Mechanical properties of an additive manufactured CF-PLA/ABS hybrid composite sheet

Laminar composites have widespread applications in the automotive and aircraft industry. This research was aimed to investigate the suitability of fused deposition modeling to produce multi-material laminar composites. Composites comprising of two dissimilar laminates, named as hybrid composites, were printed from acrylonitrile butadiene styrene filament and carbon fiber-reinforced polylactic acid filament (a composite filament) by varying different printing parameters. Tensile tests were conducted to examine the mechanical performance of the produced composite sheet. A detailed analysis of the results revealed that a high ultimate tensile strength is primarily achieved by setting low values of printing speed, layer height, and clad ratio while high elongation is obtained by employing low printing speed, medium layer height, and high clad ratio. The optimum printing conditions were sought out through desirability function with an objective to simultaneously enhance all the considered properties. Further, the composite sheet exhibited a reasonably good combination of tensile properties as compared to its monolithic constituent sheets. Based on the results, it is concluded that the bi-material laminating approach employed herein can produce printed structures with desired properties.

Thermal management applied laminar composites with SiC nanowires enhanced interface bonding strength and thermal conductivity

Thermal management applied laminar composites with enhanced interface bonding strength and thermal conductivity were fabricated through a pressure infiltration method.