We synthesized composite materials (MCs) to be used as bone tissue replacement materials. The MCs were based on non-modified hydroxyapatite (HA), hydroxyapatite functionalized with 3-aminopropyltriethoxysilane (HAF), and epoxy resin (R-Epoxy). Superficial modification was performed using a chemical method under constant stirring and reflux for 24 h at 25 degrees C. Composites were obtained by loading R-Epoxy with 5% and 10% w/w HA and HAF, respectively. To analyze the effect of HA on the polymer chain and to evaluate its influence on the crystallinity and thermomechanical properties of the MCs, morphologic, thermal, and mechanical tests were used. Flexion, compression, traction, nanoindentation, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared analyses were performed. The results indicated that HA functionalization was achieved, which led to an improvement in the mechanical properties of the MCs. The mechanical properties of the MCs obtained by reinforcing R-Epoxy with 5-10% w/w HAF were significantly improved. Likewise, the functionalization of HA improved its dispersion in the R-Epoxy matrix. Moreover, the increase in the thermal stability of the MCs was attributed to the presence of HA.