Role of Structural Hierarchy in Multiscale Material Systems

Multiscale material systems derive their effective mechanical properties through a hierarchical organization of their structural elements and components. The hierarchy of a material is related to its effective properties, material processing, and composition. The hierarchy can be defined as an identifiable structural component with a specific size scale, such as the individual fibers collimated into platelets arranged randomly and producing a complex composite system or the lamellar structure in freeze-casted ceramic with the variation of in-plane orientation. In this study, the role of the structural hierarchy on the effective mechanical response and failure behavior of three complex material systems was studied, (i) long discontinuous glass fiber reinforced Nylon composite, (ii) prepreg platelet molded composite (PPMC), and (iii) freeze-casted porous alumina ceramic. Progressive failure analysis (PFA) was used to study the damage propagation up to ultimate failure. The developed computational models provided an understanding of how the material\u27s morphology defines the variability of effective mechanical properties (modulus and strength) and the failure behavior

Spray Deposition of Sustainable Plant Based Graphene in Thermosetting Carbon Fiber Laminates for Mechanical, Thermal, and Electrical Properties

Graphene has generated substantial interest as a filler due to its exceptional strength, flexibility, and conductivity but faces obstacles in supply and implementation. A renewable, plant-based graphene nanoparticle (pGNP) presents a more accessible filler with the same properties as mineral graphenes. In this study, we examine the effects of pGNP, which was sprayed on a carbon fiber/epoxy prepreg at loadings from 1.1 to 4.2 g/m2. The study considered the mechanical, thermal, and electrical properties of pGNP-composite. An even particle dispersion was achieved using a spray application of pGNP in a water/alcohol suspension with the addition of surfactants and dispersion aides. Results show that pGNP addition increases flexural modulus 15%, flexural strength 17%, interlaminar shear strength 17%, and mode I fracture toughness by 146%, as well as increases electrical conductivity 294% and thermal conductivity 24%, with these improvements observed at 1.1–2.3 g/m2 spray loadings

Effect of Platelet Length and Stochastic Morphology on Flexural Behavior of Prepreg Platelet Molded Composites

Prepreg platelet molding compound (PPMC) can be used to create structural grade material with a heterogeneous mesoscale morphology. The present work considered various platelet lengths of the prepreg system IM7/8552 to study the effect of platelet length on the flexural behavior of PPMC composite. A progressive failure finite-element analysis was used to understand competing failure modes in PPMC with the different platelet length. The interlaminar and in-plane damage mechanisms were employed to describe complex failure modes within the mesostructure of PPMCs. Experimental results of the flexural tests of the PPMC with different platelet length sizes were used to validate the modeling prediction. The experimental and modeling results revealed complex behavior of the flexural mechanical properties (modulus and strength) on the platelet length. The experimental results indicate that PPMC composites processed with a plate length of 12.7 mm have a higher flexural modulus and strength than 25.4 and 6.35 mm. The platelet length effect on the flexural mechanical behavior was attributed to interactions between various damage mechanisms and the stochastic fiber orientation distribution variability in the material

Exergetic sustainability analysis of municipal solid waste treatment systems: A systematic critical review

The growing volume of municipal solid waste (MSW) generated worldwide often undergoes open dumping, landfilling, or uncontrolled burning, releasing massive pollutants and pathogens into the soil, water, and air. On the other hand, MSW can be used as a valuable feedstock in biological and thermochemical conversion processes to produce bioenergy carriers, biofuels, and biochemicals in line with the United Nations’ Sustainable Development Goals (SDGs). Valorizing MSW using advanced technologies is highly energy-intensive and chemical-consuming. Therefore, robust and holistic sustainability assessment tools should be considered in the design, construction, and operation phases of MSW treatment technologies. Exergy-based methods are promising tools for achieving SDGs due to their capability to locate, quantify, and comprehend the thermodynamic inefficiencies, cost losses, and environmental impacts of waste treatment systems. Therefore, the present review paper aims to comprehensively summarize and critically discuss the use of exergetic indicators for the sustainability assessment of MSW treatment systems. Generally, consolidating thermochemical processes (mainly incineration and gasification) with material recycling methods (plastic waste recovery), heat and power plants (steam turbine cycle and organic Rankine cycle), modern power technologies (fuel cells), and carbon capture and sequestration processes could improve the exergetic performance of MSW treatment systems. Typically, the overall exergy efficiency values of integrated MSW treatment systems based on the incineration and gasification processes were found to be in the ranges of 17–40% and 22–56%, respectively. The syngas production through the plasma gasification process could be a highly favorable waste disposal technique due to its low residues and rapid conversion rate; however, it suffers from relatively low exergy efficiency resulting from its high torch power consumption. The overall exergy efficiency values of integrated anaerobic digestion-based MSW processing systems (34–73%) were generally higher than those based on the thermochemical processes. Exergy destruction and exergy efficiency were the most popular exergetic indicators used for decision-making in most published works. However, exergoeconomic and exergoenvironmental indices have rarely been used in the published literature to make decisions on the sustainability of waste treatment pathways. Future studies need to focus on developing and realizing integrated waste biorefinery systems using advanced exergy, exergoeconomic, and exergoenvironmental methods