The increasing demand for lightweight, safe, and fuel-efficient vehicles has driven structural optimisation of automotive body frames. A passenger vehicle body shell was designed in SolidWorks and analysed in ANSYS Workbench 2024?R1 under frontal and rear impact at 60, 80, and 100?km/h using five material configurations: ABS, structural steel, Carbon Fiber Reinforced Polymer (CFRP), Glass Fiber Reinforced Polymer (GFRP), and a hybrid CFRP+GFRP laminate. Performance metrics — total deformation, equivalent stress, equivalent strain, and factor of safety (FOS) were extracted for each scenario. Modal analysis extracted the first six natural frequencies and mode shapes. Results show CFRP achieves superior crashworthiness (FOS?>?2.40 at all speeds) and highest natural frequencies (86.38–153.62?Hz), while the hybrid composite nearly replicates CFRP performance at reduced cost. ABS is structurally unsuitable and steel approaches failure at 100?km/h. The hybrid CFRP+GFRP laminate is the optimal lightweight alternative to conventional steel for passenger car body shell applications.