Ultrasound sonication has been widely used in the exfoliation of nanoclay platelets. Nevertheless, the existence of absolutely exfoliated nanoclay composites is impossible in reality. Regions of intercalated nanoclay platelets can be easily formed and agglomerate as tiny clusters. Different sizes of clusters mixed by nanoclays and matrix would be easily formed, particularly in the extrusion of polymer-based components. The effects of ultrasound sonication in these intercalated nanoclay clusters will be detailedly discussed in this paper. The hardness of nanoclay/epoxy composites samples made under different ultrasound sonication time will be examined to compare their mechanical performances. X-ray diffraction (XRD) technique will also be employed to investigate the interplanar distance between the nanoclay platelets in different samples. Scanning electron microscopy (SEM) will also be used to investigate the clusters distribution inside the composites. The results show that there exists an optimum ultrasound sonication time where the mechanical properties of the composites are mostly enhanced. The cluster sizes of nanoclay change with different sonicating time, whereas the interplanar distance without being altered.