Delamination is one of the most critical failure mechanisms in multilayer composites, stemming from their low interlaminar fracture toughness. In this study, nonwoven glass fiber interlayers were employed in glass/epoxy composites to enhance Mode I fracture toughness. To this end, composite specimens were fabricated using three types of base fabrics (with areal weights of 200, 400, and 600 g/m²) and two types of interlayers (with areal weights of 150 and 300 g/m²).the double cantilever beam (DCB) test was conducted in accordance with the ASTM D5528 standard, and the critical strain energy release rate was calculated using three analytical approaches: Modified Beam Theory (MBT), Compliance Calibration (CC), and Modified Compliance Calibration (MCC).

Statistical analysis of the results revealed that the coefficients of variation for the data obtained via the MBT, CC, and MCC methods were 10%, 30%, and 15%, respectively. Furthermore, a comparison of the results demonstrated favorable agreement and satisfactory accuracy among all three methods in determining Mode I fracture toughness, with the differences in the calculated GIC values assessed to be within a range of 20 to 30 percent. These findings underscore the high efficiency and reliability of these computational methodologies in evaluating the fracture properties of interlayer-reinforced composites.