Optimization of Unidirectional Carbon/Epoxy Facesheets for Enhanced Flexural Strength in PVC Foam Sandwich Beam

Sandwich composites are lightweight structures comprising stiff, thin face sheetsoften carbon or glassfibers bonded to a low-density core, delivering high strength-to-weight ratios, superior bending stiffness, and excellent energy absorption. These properties make them ideal for aerospace, automotive, and marine applications. Their performance hinges on core material selection, face sheet composition, and interfacial bonding, prompting research into optimized designs for improved mechanical behavior. This study explores the flexural performance of carbon fiber-reinforced polymer matrix composite sandwich beams by optimizing face sheet configurations. Sandwich panels were fabricated via vacuum infusion, using a Poly-vinyl Chloride (PVC) foam core and varying carbonfibers/epoxy face sheet stacking sequences 2/2, 2/4-, and 4/2-layers top/bottom in the transverse direction. Four-point bending testassessed stiffness, load capacity, and failure mechanisms. The asymmetric 4-top/2-bottom arrangement demonstrated the highest average flexural strength of 6.52 MPa, emphasizing the top layer's role in resisting tensile stresses and enhancing energy dissipation.Material characterization included Differential Scanning Calorimetry(DSC), Fourier Transform Infrared Spectroscopy(FT-IR), Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy(EDS).DSC confirmed complete epoxy curing, while FT-IR identified key functional groups. SEM revealed fiber rupture and matrix cracking as primary failure modes, with EDS detecting high carbon content, minor oxidation, and chlorine traces from the PVC core. Force-deflection and strain analyses showed asymmetric configurations exhibited more progressive, damage-tolerant failure compared to brittle symmetric sandwich composites. These findings offer critical insights into layer distribution effects, guiding the design of high-performance sandwich composites for structural applications.