Sandwich panels with PU foam core are widely used in many applications such as aerospace, chemical plant, marine and land transportation industries. Its superior weight-to-strength ratio, excellent mechanical performance, good thermal insulation and cost effectiveness make it a choice to use in these industries. This study introduces a hybrid PU-core sandwich panel incorporating a glass-fiber-reinforced layer at the mid-plane of the core, a configuration not widely reported in previous works. PU foam core with thickness of 20, 25 and 30 mm were tested using plain PU core and with a single layer of glass fibre in its core section. The failure mechanism for each sample was analyzed accordingly. Three-point bending test using UTM machine was conducted and the data produced will be used to plot the force–displacement curve and to obtain the amount of energy absorbed. The results show that increasing the core thickness does not consistently enhance the flexural strength. The sample with plain core and 25 mm thickness marked as P2 exhibit the highest flexural strength with 0.96 MPa as compared to other samples even those samples with a layer of glass fibre in its core. Sample P3 with thickness of 30 mm shows the lowest flexural strength with 0.58 MPa. F1, F2 and F3 with 18.01, 18.58 and 13.63% shows the difference in energy absorption capacity as compared to sample P1, P2 and P3 respectively. Failure analysis from each samples shows that all samples produced similar modes of failure, typically face sheet delamination, core shear and compressive failure. Samples for P3 and F3 show a distinct shear cracking in its core. From these findings, bonding effectiveness, fabrication quality and material consistency critically influence the structural performance of the sandwich panels. Future work should optimize the core designs, machine-made samples and a detailed analysis on the failure mechanism through numerical or microstructural observation to enhance the effectiveness of using lightweight yet strong sandwich structures.