Polylactic acid (PLA) and graphene reinforced polylactic acid (PLA‐graphene) composites have been fabricated by three‐dimensional (3D) fused deposition modeling (FDM) printing. Indentation creep resistance was analyzed in terms of the strain‐rate sensitivity index of PLA (0.11) and PLA‐graphene (0.21). Enhanced creep resistance in PLA‐graphene is attributed to the restriction of the polymeric chains by graphene, caused by low strain rates identified during secondary creep. The tribological properties of PLA and PLA‐graphene composites were evaluated by ball‐on‐disk wear tests. Wear resistance was increased by a 14% in PLA‐graphene as compared to PLA. A two‐stage coefficient of friction (COF) behavior has been observed for PLA‐graphene. Initially, PLA‐graphene exhibits a 65% decrease in COF as compared to PLA. During the second stage, PLA‐graphene approached similar COF behavior and value of PLA (∼0.58). PLA‐graphene composites have shown significant improvement in creep and wear resistance demonstrating 3D printing to be a novel manufacturing route. POLYM. COMPOS., 39:3877–3888, 2018. © 2017 Society of Plastics Engineers

The adhesion of ice severely compromises the aerodynamic performance of aircrafts operating under critically low-temperature conditions to their surfaces. In this study, highly thermally and electrically conductive graphene foam (GrF) polymer composite is fabricated. GrF-polydimethylsiloxane (PDMS) deicing composite exhibits superior deicing efficiency of 477% and electrical conductivities of 500 S m with only 0.1 vol % graphene foam addition as compared to other nanocarbon-based deicing systems. The three-dimensional interconnected architecture of GrF allows the effective deicing of surfaces by employing low power densities (0.2 W cm). Electrothermal stability of the GrF-PDMS composite was proven after enduring 100 cycles of the dc loading-unloading current. Moreover, multifunctional GrF-PDMS deicing composite provides simultaneous mechanical reinforcement by the effective transfer and absorption of loads resulting in a 23% and 18% increase in elastic modulus and tensile strength, respectively, as compared to pure PDMS. The enhanced efficiency of the GrF-PDMS deicing composite is a novel alternative to current high-power consumption deicing systems.

The growing demand for a sustainable leather industry with a low environmental impact has prompted the development of alternative vegetable-based materials. In this study, a biodegradable mushroom-based leather derived from the fruiting body of Phellinus ellipsoideus is investigated. The biodegradable leather proves to be thermally stable up to 250 °C. The mechanically robust macrostructure combines a tensile strength of 1.2 MPa and ductility (101% strain at break) attributed to the natural balance of chitin (0.3) and proteins (0.7) constituting the mycelium fibers. The chitin–protein system results in an intrinsic scratch-resistant structure with exciting damping properties in a low frequency range. Enhanced damping capabilities within 5–20 Hz (tan δ: 0.1–0.20) are attributed to the macrostuctural alignment of the mycelium under cyclic tension. Whereas, increasing frequencies >20 Hz induce micromolecular interactions between chitin and proteins within the fibers. Exposure of the bioleather to acidic (pH 4, 5) and basic (pH 8, 9) media demonstrated the selective dissolution of proteins (basic) and chitin (acid) components within the mycelium, opening an opportunity for tunable mechanical response. Reducing the protein content induced an increase in stiffness and strength (pH 8 and 9), while reducing its chitin component showed variable ductility (pH 4 and 5). Owing to the entirely natural composition of the mushroom leather, intrinsic antifungal and antibacterial properties found in the mycelium resist fungal invasion and bacterial growth. Thus, this study displays the unique morphology–property relationship of a biodegradable mushroom leather, proving its potential as a fully sustainable and environmentally friendly alternative.

Photosensitive polymer-based boron nitride nanoplatelets (PSP/BNNP) composites are fabricated via stereolithography (SLA) three-dimensional (3D) printing technique. The influence of the BNNP addition on the curing, and the resulting microhardness, damping, and compressive strength is evaluated in composites with 0, 0.5, and 1 wt% BNNP. Damping response in 1 wt% BNNP composites was found to exhibit loss tangent (tan d) values 23 higher than pure PSP (0.07-0.17). Enhanced damping properties in composites are attributed to the interfacial shearing and sliding of BNNP. The potential of BNNP as a reinforcement in SLA 3D printing scaffolds is shown by a 23.8% increase in compressive yield strength in 1 wt% BNNP as compared to 0.5 wt% BNNP. It is observed that interaction of the nanoparticles with the laser wavelength during the curing process is of prime importance in the successful manufacturing of 3D printed structures with improved functional properties. POLYM. COMPOS., 00:000-000, 2017. FIG. 7. UV-Vis absorbance spectrum of 0 and 1 wt% BNNP composite resins at UV wavelengths 350-425 nm. [Color figure can be viewed at wileyonlinelibrary.com]

Full densification of a Ti alloy (Ti6Al4V) is achieved at unprecedented low temperatures of 650 °C and 555 MPa by spark plasma sintering (SPS) without any sintering aid. The alloy demonstrates a globular equiaxed microstructure with comparable mechanical properties as that sintered at conventional high temperatures (950 °C, 60 MPa). In contrast with the diffusion‐driven sintering of the Ti alloy at conventional SPS conditions, the near‐full densification (99%) attained at low‐temperature/high‐pressure regimes is attributed to plastic deformation‐driven mass transport processes. Sintering pressures of 555 MPa result in a dislocation dense microstructure and the activation of compressive twins imparting lattice strains of up to 2.86 × 10−3, suggesting a 25% increase in lattice distortions as compared with those sintered at moderate pressures of 60 MPa. Depth‐sensing nanoscale indentation reveals the globular microstructure of the high‐pressure‐sintered alloy to retain its elastic modulus and hardness of 138 and 4.8 GPa, respectively, with <2% deviation from those sintered at conventional SPS temperatures. This energy‐efficient technique proposes an alternative to thermally exhaustive routines and presents an advantage for engineering titanium‐matrix composites with nanofillers and controlled reaction products by reducing processing temperatures by up to 300 °C.