Flexural strength behavior in pultruded GFRP composites reinforced with high specific-surface-area biochar particles synthesized via microwave pyrolysis

This research focuses on the development of novel biocomposites with improved flexural strength properties, obtained from merging conventional pultruded glass FRP (GFRP) composites with carbon-based biochar particles synthesized via microwave MW) pyrolysis method. A comprehensive design-of-experiments is carried out by varying: (1) biomass feedstock, (2) MW processing parameters, and (3) biochar vol.% in the pultrusion biocomposites manufacturing process. Results show over two times flexural strength gain in biocomposites reinforced with a 10 vol% biochar, from 450 MPa to 970 MPa, without compromising tensile strength. The increase in flexural strength is attributed to a combination of high SSA and the hardness of the biochar particles. High hardness enhanced the biocomposites compressive performance during bending, causing the failure mechanism to shift from compressive-dominant to tensile-dominant. High porosity of the biochar created a mechanical interlocking between the honeycomb structure of the biochar and the cured polymer matrix.