Assessment of hybrid nanocomposite AFOs for pediatric cerebral palsy: mechanical, spectroscopic, and finite element analysis

Abstract

Abstract Cerebral Palsy (CP) is a neurological disorder that affects motor function and causes gait abnormalities in children. Ankle–Foot Orthoses (AFOs) are external aiding devices that provide stability and improve mobility for pediatrics. However, conventional AFO materials often fail to achieve an optimal balance of strength, flexibility, and energy absorption for dynamic movements. This study introduces a novel composite material for pediatric ankle–foot orthoses (AFOs), based on Orthocryl and reinforced with multi-walled carbon nanotubes (MWCNTs) and polylactic acid (PLA). The proposed formulation is engineered to overcome the limitations of conventional materials by providing enhanced mechanical performance and improved functional suitability for clinical applications. Four composite concentrations were fabricated: pure Orthocryl, 0.5% MWCNTs, 0.5% MWCNTs/1.0% PLA, and 0.5% MWCNTs/1.5% PLA. Mechanical and morphological characterizations were performed using a universal testing machine for tensile, flexural, and impact testing, Fourier Transform Infrared Spectroscopy (FT-IR) for material composition analysis, and Field Emission Scanning Electron Microscopy (FE-SEM) for surface morphology examination. To simulate practical application, Finite Element Analysis was performed using ANSYS software, recognizing gait loading conditions. The experimental findings demonstrated that incorporating 0.5% MWCNT into Orthocryl significantly enhanced its mechanical properties, with a 12.5% increase in tensile strength (from 52.79 to 59.4 MPa), a 59.3% increase in flexural strength (from 52.08 to 82.93 MPa), and a 22% improvement in impact resistance (from 28.12 to 34.3 kJ/m2). These improvements confirm the effectiveness of MWCNT reinforcement. Additionally, FE-SEM and FT-IR analyses confirmed the uniform distribution of CNTs within the matrix and stronger interfacial bonding between the filler and polymer. Simulation results showed that the 0.5% MWCNT/1.5% PLA composite had the highest deformation (10.95 mm) with a safety factor of 1.12, indicating acceptable safety. In contrast, the 0.5% MWCNT composite showed the lowest deformation (4.17 mm), 12.6% less than pure Orthocryl, and the highest safety factor (3.2), reflecting an optimal balance of strength and flexibility for pediatric AFOs in CP patients.