Algae is a promising sustainable feedstock for the generation of bio-crude oil, which is a sustainable alternative to fossil fuels, through the thermochemical process of hydrothermal liquefaction (HTL). However, this process also generates carbon particles (algae-derived carbon, ADC) as a significant byproduct. Herein, we report a brand-new and value-added use of ADC particles as a reinforcing agent for epoxy matrix composites (EMCs). ADC particles were synthesized through HTL processing of Chlorella vulgaris (a green microalgae) and characterized for morphology, average size, specific surface area, porosity, and functional groups. The ADC particles were subsequently integrated into a representative epoxy resin (EPON 862) as a reinforcing filler at loading levels of 0.25%, 0.5%, 1%, and 2% by weight. The tensile, flexural, and Izod impact properties, as well as the thermal stability, of the resulting EMCs were evaluated. It is revealed that the ADC particles are a sustainable and effective reinforcing agent for EMCs at ultra-low loading. Specifically, the ADC-reinforced EMC with 1 wt.% ADC showed improvements of ~24%, ~30%, ~31%, and ~57% in tensile strength, Young’s modulus, elongation at break, and work of fracture (WOF), respectively, and improvements of ~10%, ~37%, ~24%, and ~39% in flexural strength, flexural modulus, flexural elongation at break, and flexural WOF, respectively, as well as an improvement of ~54% in Izod impact strength, compared to those corresponding properties of neat epoxy. In the meantime, the thermal decomposition temperatures at 60% and 80% weight loss of the abovementioned ADC-reinforced EMC increased from 410 °C to 415 °C and from 448 °C to 515 °C in comparison with those of neat epoxy. This study highlighted the potential of sustainable ADC particles as a reinforcing agent in the field of polymer matrix composite materials, which represented a novel and sustainable approach that would mitigate greenhouse gas remission and reduce reliance on nonrenewable reinforcing fillers in the polymer composite industry.

This chapter discusses the fabrication and mechanical characterization of nano-engineered composite laminates fabricated using variable-thickness graphene sheets incorporated in non-crimp carbon fiber prepregs. The effect of graphene sheet thickness on interlaminar strength (Mode I fracture toughness) of the carbon fiber composites was evaluated. The graphene lattice structure used in the present research had linear and square grids. Linear grids were arranged parallel and perpendicular to the 0° fibers in the composite laminates and labeled as vertical and horizontal grid patterns, respectively. Mechanical characterization involved the study of the effects of sheet thickness and grid pattern with and without nanoengineered enhanced laminates at the midplane. The composite laminates fabricated using a lattice graphene structure had better interlaminar strength than those fabricated with straight graphene sheets. Nanoengineered sheets with minimal thickness showed better interlaminar strength than the thicker sheets. The polymer used to manufacture the graphene sheet could not bond with the epoxy used in the composite laminate. In the literature, when the graphene nanoparticles are dispersed in the epoxy, the challenge is a uniform distribution of the nanoparticles. To overcome this dispersion problem, sheets made using nanomaterials can be used to enhance the mechanical properties of the composite laminates.