Basalt-silk fiber reinforced PLA composites: Effect of graphene fillers and stacking sequence

This study explores the development of biocompatible composites using strong basalt fibers and ductile silk fibers, and a polylactic acid (PLA) matrix. Five distinct stacking sequences were fabricated via a replicable hand layup and vacuum bagging technique, with alternating layer specimens (ALT) further enhanced by the addition of graphene nanoplatelets (GNPs) at 3, 6, and 9 wt.% of the PLA matrix. The composites were characterized for tensile, flexural, impact, and interlaminar shear strengths, damping properties, electrical conductivity, moisture absorption, and morphological features. The ALT configuration exhibited superior performance, with its multi-layered structure effectively mitigating delamination. ALT composites without GNPs achieved the highest tensile strength (136.54 MPa), tensile modulus (3.42 GPa), interlaminar shear strength (0.48 MPa), impact energy (36.84 kJ/m²), and flexural strength (18.06 MPa), predominantly failing via delamination. SEM analysis identified the basalt fiber-PLA interface as a critical failure site. The incorporation of 6 wt.% GNP enhanced damping by 1.54 times, but the composites remained nonconductive due to graphene agglomeration and lack of a conductive network. These energy-absorbing, environmentally sustainable composites show promise for multifaceted applications with reduced ecological impact.