A fiber placement device is described and methodology is given for preparing two-dimensional (2-D) and three-dimensional (3-D) combinatorial microcomposites. Although 2-D microcomposites with uniform fiber spacing have been prepared previously, the preparation of uniformly spaced 3-D microcomposites with 6-20 mu m diameter fibers is new. The preparation of these combinatorial specimens was motivated by research results from reference [Li et al. (1995) Compos Sci Technol 54:251]. These results showed that the mean fragment length of the broken fibers in an array of fibers of the shear-lag models increases as the inter-fiber separation decreases. It was noted that shear-lag theory predicts the opposite effect. Therefore, specimens of this type are needed to unambiguously verify this trend. In addition, data from this new technology should delineate the factors that influence critical flaw nucleation in unidirectional laminate composites.