Effect of Fiber Orientation on Impact Behavior and Hardness of VARTM-Manufactured GFRP and CFRP Composites

This study examines the Charpy impact response and surface hardness of glass fiber–reinforced polymer (GFRP) and carbon fiber–reinforced polymer (CFRP) laminates produced viaVacuum Assisted Resin Transfer Molding (VARTM). Notched specimens with three distinct plyorientations—0°, 0/90°, and 30°—were evaluated experimentally, and failure surfaces werecharacterized by stereo microscopy (SM). Among the orientations examined, the 30° configurationyielded the greatest energy absorption in both material systems. GFRP laminates consistentlyoutperformed their CFRP counterparts in impact capacity, recording roughly 46% higher absorbedenergy. The orientation-induced improvement was considerably more marked for CFRP(approximately 213%) than for GFRP (approximately 76%). One-way analysis of variance(ANOVA) confirmed the statistical significance of ply orientation on impact response, and residualexamination verified that no data points deviated beyond ±2 standard deviations. Moreover,fractographic evaluation indicated that GFRP specimens failed mainly by fiber pull-out and elasticdeformation of the fiber–matrix interface at oblique orientations, whereas CFRP laminatesdisplayed a brittle fracture character involving fiber breakage, interfacial debonding, andinterlaminar splitting. The collective results underscore the decisive roles of fiber type and plyorientation in controlling impact performance and damage evolution in VARTM-processed epoxycomposites.