We report the synthesis of a three-dimensional (3D) macroassembly of graphene sheets with electrical conductivity (∼10(2) S m(-1)) and Young's modulus (∼50 MPa) orders of magnitude higher than those previously reported, super-compressive deformation behavior (∼60% failure strain), and surface areas (>1300 m(2) g(-1)) approaching theoretically maximum values.
Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignment within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Furthermore, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.
an exponent, n , in the range of 2-4, Figure 4 a shows a density dependence of the modulus for a number of carbon materials, including carbon aerogels, [ 27 ] carbon-nanotube (CNT) assemblies [ 29 ] , graphene, [ 4,10 ] graphene-based materials, [ 18,36,37 ] and graphite. [30][31][32] Figure 4 a shows that the modulus of the GDC scales with density as expected for CNT-or
Octa-OH-functional POSS has been incorporated into a model polyurethane elastomer as a comparatively massive and notionally "robust" 3-dimensional cross-linking core. The effects of this cross-linking moiety on the morphology and molecular dynamics of the system are studied over a range of size and time scales. Microscopy, scattering, spectroscopic, thermal, and dielectric techniques, in agreement with each other, show that the covalent inclusion of the crosslinking particles restricts microphase separation, inhibits the formation of hard-block domains, and decelerates the motional dynamics of the polyurethane backbone. The effects on both the morphology and the dynamics of the polyurethane system are not continuous but occur in a steplike manner in the loading region of 4−6 wt % POSS. This critical region is thought to correspond to a sterically induced transition from one dominant morphology (microphase segregated) to an increasingly homogeneous nanophase segregated domain morphology. Contrary to expectations, cross-linking, even by the presumably rigid siliceous nanoparticles, reduces the mechanical modulus. In conjunction with the reduction of microphase separation, this observation indicates that the hard microdomains reinforce the polymer more effectively than the chemical cross-links.
Shape memory polymers (SMPs) are attractive materials due to their unique mechanical properties, including high deformation capacity and shape recovery. SMPs are easier to process, lightweight, and inexpensive compared to their metallic counterparts, shape memory alloys. However, SMPs are limited to relatively small form factors due to their low recovery stresses. Lightweight, micro-architected composite SMPs may overcome these size limitations and offer the ability to combine functional properties (e.g., electrical conductivity) with shape memory behavior. Fabrication of 3D SMP thermoset structures via traditional manufacturing methods is challenging, especially for designs that are composed of multiple materials within porous microarchitectures designed for specific shape change strategies, e.g. sequential shape recovery. We report thermoset SMP composite inks containing some materials from renewable resources that can be 3D printed into complex, multi-material architectures that exhibit programmable shape changes with temperature and time. Through addition of fiber-based fillers, we demonstrate printing of electrically conductive SMPs where multiple shape states may induce functional changes in a device and that shape changes can be actuated via heating of printed composites. The ability of SMPs to recover their original shapes will be advantageous for a broad range of applications, including medical, aerospace, and robotic devices.
We report 3D printing of a ‘pure’ thermal cure cyanate ester for the fabrication of robust 3D printed structures through the formulation, tailoring and post processing of a custom ‘ink’ for Direct Ink Writing.
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