<![CDATA[This study evaluates the effects of manufacturing method and fiber orientation on the mechanical performance of carbon fiber-reinforced polymer (CFRP) composites for automotive applications. Unidirectional CFRP laminates were fabricated using vacuum bagging (VB), vacuum-assisted resin infusion (VARI), and hand lay-up (HLU). Specimens with 0° and 90° fiber orientations were tested under tensile and compressive loading, while ±45° specimens were evaluated for in-plane shear response through tensile testing. Short-beam and V-notched beam tests were conducted to determine interlaminar shear and shear properties. Microstructural characterization of the manufactured laminates and fractured specimens was performed using CT-scan and SEM, supported by finite element validation. Unlike previous studies focusing on limited properties or a single manufacturing route, this work provides a comprehensive comparison of HLU, VB, and VARI CFRP laminates by integrating mechanical testing, defect analysis, fracture observations, and numerical assessment. The results show that VARI produced superior laminate compactness and the highest tensile-related properties, although this improvement did not correspond to higher interlaminar shear strength, highlighting the influence of manufacturing-induced laminate architecture. For 0° specimens, ultimate tensile strengths were 507.72 ± 52.14 MPa for HLU, 685.69 ± 62.65 MPa for VB, and 774.31 ± 58.18 MPa for VARI. At ±45°, tensile strengths were 20.85 ± 0.82, 21.20 ± 0.45, and 22.18 ± 0.81 MPa, respectively. At 90°, manufacturing method had no significant effect on tensile strength, although tensile modulus remained method-dependent. The highest 0° compressive strength was obtained by HLU at 124.8 ± 13.1 MPa, whereas VARI showed the highest 90° compressive strength at 44.60 ± 0.82 MPa. VARI exhibited lower shear and interlaminar shear strengths of 15.31 ± 1.01 and 13.68 ± 0.85 MPa, respectively, indicating that increased fiber volume fraction did not substantially improve these properties. Nevertheless, VARI achieved the highest tensile and shear moduli, reaching 39.31 ± 4.58 GPa and 1.50 ± 0.15 GPa. Microstructural observations confirmed that improved resin distribution, reduced defects, and stronger fiber–matrix bonding in VARI contributed to enhanced overall mechanical performance. These findings demonstrate that manufacturing route governs different failure mechanisms and should therefore be selected according to the dominant loading mode and required laminate properties.]]>
