A systematic study of the internal friction (IF) of an epoxy-diaminodiphenylmethane (DDM) blend polymer containing nanometre-sized Al2O3 (n-Al2O3) particles with various filling factors F-f was carried out. It was found that the beta-IF peak and the modulus of the composite materials depended strongly on F-f. The height of the beta peak first increases and then decreases gradually with increasing F-f. When F-f>0.05, the beta peak drops substantially. However, the modulus of the composite materials first decreases with increasing F-f. When F-f>0.05, the modulus increases dramatically. The experimental results show that the added amount of n-Al2O3 particles strongly affects the mechanical properties of the composites. A detailed discussion and explanation of the influence of n-Al2O3 particles on the behaviour of the beta peak and modulus of the composites are presented in this paper.