Various peel-off experiments can be used to determine the adhesion strength of various fibres. Among them was the "T" type peel-off test, which measures the adhesions between fibres. The use of organic and inorganic fillers in flake or powder form will alter the adhesive properties of the binders as well as the adhesive strength between the fibres. In this study, the adhesion strength between three different varieties of glass fibres (C-Glass, E-Glass, and S-Glass fibres) with a PLA core has been investigated. As a binder, an epoxy resin was used, and the resin was modified with inorganic additives such as alumina, bentonite, and silicon carbide. Peel-off testing was used to examine the effect of additives on the bonding strength between a thermoplastic core and a synthetic fibre. The addition of inorganic compounds was found to reduce the adhesion strength between the fibres and the core. In order to evaluate the initial adhesion between the filaments and the core, nine specimens were fabricated without the addition of any additives and their strengths were determined. Maximum adhesion strength of 71.8 MPa was recorded for the neat resin. The adhesive strength after inclusion of additives was observed to decrease by 18.14%, and recorded maximum peel-off strength of 58.2 MPa. Also, the inclusion percentages of the additives were found to be the most influential factor in determining the composites' adhesive properties. Validation tests were also conducted with the optimized results which demonstrated that the predicted and experimental results were in excellent agreement. Macro and micro approaches were employed to analyze the deformation mechanisms in order to gain a comprehensive understanding of how the additives affected the adhesion strength.