Load transfer mechanisms in the platelets reinforced composites with considering the interphase related failure modes

The interphases have a significant influence on the overall mechanical properties of layered composites. Many of these interphases between the reinforcement and matrix have specific thickness and mechanical properties that differ from those of the matrix. A theoretical model that addresses interphase with limited thickness is developed to explain the load transfer mechanisms and failure behaviors of the platelets reinforced composites with interphase. A universal and concise definition of load transfer efficiency is established to characterize the load transfer capability of the reinforcement in the composites with interphase. The results show that though the effective Young's modulus of the composites can be enhanced by increasing thickness or Young's modulus of the interphase, the load transfer to the reinforcement is limited due to that more external load is carried by the thicker and harder interphase. A competitive mechanism among the three major failure modes is revealed, including interphase cracking, interphase/matrix debonding and interphase/platelet debonding. Interphase cracking dominates only when the tensile strength of the interphase is lower or comparable to the shear strength of the interphase. Otherwise, interphase/matrix debonding occurs with hard and thick interphase, while interphase/platelet debonding occurs with thin or soft interphase. This study provides a fundamental understanding of the role of the interphase in the mechanical behaviors of the platelets reinforced composites, which can be helpful to modulate the mechanical properties of composites through interphase design.