Comparative mechanical and microstructural characterization of transfemoral prosthesis sockets reinforced with carbon and flax fibers

This study compares the mechanical, dynamic, and damage behavior of transfemoral prosthetic sockets manufactured from carbon-fiber (OPNC) and flax-fiber (OPNF) composites using vacuum molding with C-Orthocryl resin. Standardized specimens were subjected to tensile, three-point bending, and split-disk tests, while impulse excitation and acoustic emission (AE) analyses were employed to investigate dynamic stiffness, damping, and damage evolution. Fracture surfaces were characterized using scanning electron microscopy (SEM). Under tensile loading, OPNC exhibited higher strength and stiffness (79.9 MPa and 11.9 GPa) than OPNF (63.2 MPa and 6.1 GPa). Similarly, OPNC showed greater circumferential strength in split-disk tests (25.45 MPa) compared with OPNF (19.64 MPa). However, OPNF demonstrated higher strain to failure and a more progressive damage evolution, indicating lower brittleness and greater deformability. In bending, both laminates displayed comparable stiffness, with flexural moduli of 4.83 GPa for OPNC and 4.72 GPa for OPNF. Dynamic analysis revealed higher resonance frequency and damping factor for OPNF (786 Hz and 0.044) than for OPNC (730 Hz and 0.035), whereas OPNC retained a slightly higher dynamic modulus (7.78 GPa vs 7.38 GPa). AE monitoring showed gradual damage accumulation in OPNF, dominated by matrix cracking and delamination, while OPNC exhibited abrupt energy release associated with brittle fiber fracture. SEM observations confirmed stronger interfacial adhesion in OPNF and rapid crack propagation in OPNC. Overall, flax-fiber composites provided a balanced combination of mechanical integrity, damage tolerance, vibration damping, and sustainability, highlighting their potential as an alternative to carbon-fiber composites for prosthetic socket applications.