This work involves the development of a novel siliconized epoxy interpenetrating system using DGEBA LY556 epoxy resin  as base, hydroxylterminated polydimethylsiloxane (HTPDMS) as modifier,γ-aminopropyltriethoxysilane (γ-APS) as crosslinking agent and dibutyltindilaurate (DBTDL) as catalyst. Triethylenetetramine (TETA) was used as curing agent for the above system. Electrical resistant glass (E-glass) and Spectra ultra high molecular weight polyethylene (UHMWPE) reinforced composites are fabricated by hand-lay-up technique using siliconized epoxy matrix systems. The effect of the percentage of siloxanes and the two fibers on the thermal and morphological characteristics of the siliconized epoxy polymer composites are studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC). From the study, it is observed that the thermal stability of epoxy systems is enhanced when siloxane is incorporated to them. Morphological studies show that E-glass fiber reinforcement has better intermolecular adhesion to epoxy resin than Spectra reinforcement due to the presence of ionic sites.