Experimental and theoretical investigation on tensile properties and fracture behavior of carbon fiber composite laminates with varied ply thickness

Abstract Unidirectional laminate made from ply prepreg is commonly used to evaluate the mechanical performance of carbon fiber-reinforced composites (CFRCs), which is often calculated using the classical law of mixtures based on the fraction of dual-phases components. The thinning of the ply prepreg presents some special influences on composite structures and mechanical properties, leading to the deviation of the results between calculation and the experiment. In this work, four CFRC laminate with varied ply thickness from 0.02 mm to 0.1 mm were fabricated, using a new type of spreading technique which combined airflow with mechanical spreading, to explore thinning effect of the ply on the fiber alignments, the tensile properties and fracture behaviors of the laminates. The observed morphological structure and the tested tensile properties suggest that the fine alignment of the CFs in the matrices, caused by the ultra-thinning of the ply, reduces fiber deflection and resin-rich region, which further improves the mechanical properties and the interlaminated fracture resistance of the CFRC laminates. A prediction model of the mechanical properties was proposed accordingly by introducing an equivalent coefficient, which is a function representing the deflection angle, as an adjustment of the law of mixtures in dual-phases of composites materials. The predicted results are well in agreement with the experimental ones, suggesting that the proposed method is an efficient way to understand the mechanical properties of the CFRC laminates.