Cellulose nanocrystals (CNCs) is a promising biodegradable nanomaterial with outstanding physical, chemical, and mechanical properties for many applications. Although aligned CNCs can self-assemble into bundles, their mechanical performance is reduced by interfacial strength between CNCs and a twisted structure. In this paper, we employ developed coarse-grained (CG) molecular dynamic (MD) simulations to investigate the influence of twist and interface energy on the tensile performance of CNC bundles. CNC bundles of different sizes (number of particles) are tested to also include the effect of size on mechanical performance. The effect of interfacial energy and twist on the mechanical performance shows that elastic modulus, strength, and toughness are more sensitive to twisted angle than interfacial energy. In addition, the effect of size on the bundle and twist on their mechanical performance revealed that both size and twist have a significant effect on the results and can reduce the strength and elastic modulus by 75% as a results of covalent bond dissociation. In addition, a comparison of the broken regions for different values of twist shows that by increasing the twist angle the crack propagates in multiple locations with a twisted shape.

Performance of the nanoparticle-modified asphalt binder is greatly influenced by adhesion properties between asphalt binder and nanoparticle. In this work, the adhesion properties of crude oil fractions (e.g., Saturate, Asphaltene, Resin and Aromatic components of asphalt binder), graphene and mineral aggregates (silicon dioxide) at various temperatures are investigated through molecular dynamic simulation and REAXFF force field. The results from SARA-graphene interface demonstrations that aromatic and asphaltene have 30% higher adhesion properties than saturate and resin. Also, while using graphene is valuable for the adhesion properties of the binder, it has no significant advantage over binder in binder-aggregate interactions.

The Vibro-Acoustic Modulation (VAM) method utilizes nonlinear interaction of a high frequency ultrasonic wave (carrier signal) with frequency ω and a low frequency modulating vibration with frequency Ω << ω, in the presence of various flaws such as fatigue and stress-corrosion cracks, disbonds, etc. Most of the reported VAM studies correlate flaw presence and growth with the increase in the Modulation Index (MI) defined in the spectral domain as the ratio of the side-band spectral components at frequencies ω±Ω to the amplitude of the carrier. This approach, however, does not differentiate between amplitude, AM, or frequency, FM, modulations contributing to the MI. It has been assumed that the prevailing modulation is AM due to contact-type nonlinear mechanisms. However, there could be other mechanisms leading to phase/frequency modulation. The present study aims to develop an algorithm of AM/FM separation specifically for the VAM method. It is shown that the commonly used Hilbert Transform (HT) separation may not work for a typical VAM scenario. The developed In-phase/Quadrature Homodyne Separation algorithm addresses HT shortcomings. The algorithm has been tested both numerically and experimentally (for fatigue crack evolution) showing FM dominance at initial micro-crack growth stages and transition to AM dominance during macro-crack formation.

The adhesion properties of mineral aggregates (SiO₂) and carbon nanotube (CNT) are estimated and compared with CNT-saturate, asphaltene, resin, and aromatic (SARA), SARA-SiO₂ , and Graphene-SARA using molecular dynamics (MD) and reactive force field. The effect of electrostatic (ES), van der Waals (vdW) and bonded interactions on the adhesion properties at room temperatures are analyzed. The results show that the strength and work of adhesion for CNT-SARA is lower than Graphene-SARA as they provide less effective area. Also, vdW and ES interactions in SiO₂-SARA and SiO₂-CNT interfaces are equally important, while in CNT-SARA interface only vdW interactions have the major contribution.