Interface stress transfer model and modulus parameter equivalence method for composite materials embedded with tensile pre-strain shape memory alloy fibers.

The constitutive model and modulus parameter equivalence of shape memory alloy composites (SMAC) serve as the foundation for the structural dynamic modeling of composite materials, which has a direct impact on the dynamic characteristics and modeling accuracy of SMAC. This article proposes a homogenization method for SMA composites considering interfacial phases, models the interface stress transfer of three-phase cylinders physically, and derives the axial and shear stresses of SMA fiber phase, interfacial phase, and matrix phase mathematically. The homogenization method and stress expression were then used to determine the macroscopic effective modulus of SMAC as well as the stress characteristics of the fiber phase and interface phase of SMA. The findings demonstrate the significance of volume fraction and tensile pre-strain in stress transfer between the fiber phase and interface phase at high temperatures. The maximum axial stress in the fiber phase is 705.05 MPa when the SMA is fully austenitic and the pre-strain increases to 5%. At 10% volume fraction of SMA, the fiber phase's maximum axial stress can reach 1000 MPa. Ultimately, an experimental verification of the theoretical calculation method's accuracy for the effective modulus of SMAC lays the groundwork for the dynamic modeling of SMAC structures.

Research on nonlinear response analysis of micro-cracks under vibro-acoustic modulation.

In view of the complex nonlinear interaction mechanism between acoustic waves and damage in vibration sound modulation technology, this paper derives the kinematic equilibrium equation for linear elastic materials with cracks undergoing infinitesimal deformation using structural mechanics theory. The weak form of the equation is derived by applying the principle of virtual work to calculate the virtual work due to nonlinear changes in crack spacing. This paper also explains the physical origin of high harmonic and sideband signals in the system displacement solution. In addition, a three-dimensional contact model of micro-cracks is constructed to describe the nonlinear effect of contact sound on the crack surface caused by relevant displacement fields. To verify the correctness of the model, two indicators, the modulation index and the damage index, are used to evaluate the simulation results. The results indicate that the interface contact under micro-crack opening and closing motions causes additional nonlinear frequencies and that the nonlinear response increases with excitation amplitude while being relatively sensitive to micron-level cracks. Finally, experimental research is conducted, which confirms the theoretical derivation, and the reliability of the model has been verified.