Acoustic Study of Elasticity and Damping Properties of Polypropylene Composites Reinforced with Titanium Nitride Particles for 3D Printing

Composite materials reinforced with titanium nitride particles, which serve as the basis for manufacturing 3D-printed components that are promising for use in extreme environments, such as cutting tools, wear-resistant and protective coatings, biomedical products, and electrochemical energy capacitors, were studied. Linear and nonlinear acoustic methods were employed to evaluate the elastic and damping properties of polypropylene-based composites reinforced with up to 46 vol.% titanium nitride particles. When the volume content of titanium nitride particles raised from 20% to 46%, Young’s modulus of the composites was found to increase from 4.91 to 9.77 GPa and their shear modulus from 1.85 to 3.55 GPa. The dependence of both elastic moduli on the ceramic volume content over the studied range can be described with satisfactory accuracy by the Halpin–Tsai equation, using an empirical reinforcement particle shape factor of 4.2, which closely matches the experimentally determined value. The damping capacity of the studied composites ranged from 0.06 to 0.12 and was slightly lower in the composite with the higher titanium nitride content. The damping behavior of the composites as a function of the maximum cyclic strain amplitude exhibited a minimum at stress levels around 2.5 MPa. At the same stress levels, a discontinuity in the amplitude dependence of the relative resonance frequency shift was observed. The authors attribute both phenomena to structural transformations within the composite that occur during cyclic deformation under the specified amplitudes and oscillation frequencies. The results demonstrate the potential of acoustic nondestructive methods to monitor the quality of filaments for 3D printing and finished composite products.