This study treats the mechanical behavior of composites, made of an epoxy resin matrix reinforced at 30% and 40% with a satin cloth type of long Alfa fibers, Sisal and hybrid Alfa/Sisal. The fibers are obtained by extraction with elimination of binders such as pectins and lignin. For each type of fibers, an appropriate and optimal chemical and thermal treatments duration are conducted within NaOH solution. FTIR, SEM and chemical decomposition of treated and untreated fibers leads to prove the efficiency of the treatment. Differential scanning calorimetry made it possible to quantify the enthalpy changes of materials as a function of temperature and TGA, DTG also showed better thermal stability. DSC showed an increase in the amount of heat as a function of the increase in volume fraction of fibers. The endothermic reaction of the studied composites containing 30wt% fiber reinforcement is lower than that containing 40wt% fiber reinforcement. The composite materials are performed by VARTM due to hydrophilic fibers nature. The results of static tensile, the 3-point bending and compression tests of different specimens were compared to those of the pure epoxy resin. It showed a significant increase in Young's modulus. Best results are shown for 40wt% woven Alfa fibers/Epoxy of about 333%, 113%, and 81% on tensile, 3-points bending and compression tests respectively. The SEM morphology analysis of both untreated and treated fiber surfaces show clean and clearly visible fibers after alkali treatment and its breaking mechanism revealed good interfacial adhesion between the treated fiber and the matrix.