Unidirectional (UD) composite laminates based on carbon fibers (CF) and high-performance polyethylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at 25 degrees C, followed by heating at 55 degrees C (well below the softening point of PEF) for 2 h. The viscoelastic behavior of the composite was studied through dynamic mechanical analysis at different volume fractions of the fibers. Several parameters such as the storage modulus (E＇), loss modulus (E "), and loss factor or damping efficiency (tan delta) were determined between 40 and 160 degrees C in a resonant frequency mode. The glass transition temperature (T-g) increased to a higher region with increase in the volume of PEF in the hybrid laminates. It was also observed that the efficiency of the composite decreases with increase in the volume fraction of the fibers.