The random critical-core model is adapted to investigate the tensile failuremechanism and hybrid effect of unidirectionally arrayed hybrid composites with alternating low andhigh elongation fibers. By utilizing the model in conjunction with the results of the stressconcentration analysis in which the interfacial damage between fiber and matrix is considered, amicroscopic statistical analysis of both the first failure and ultimate failure of hybrids isperformed. The variations of the first failure strain, the ultimate failure strain and the hybrideffect as the interfacial shear strength are obtained quantitatively. The concept of the hybrideffect for strains has been clarified. The present results are compared with available experimentdata and a reasonable agreement is found between the analytical predictions and the experimentalresults.
