Internal Morphology Evolution of Mg Wire/Poly(Lactic Acid) Composites during Degradation Process Characterized by X-Ray Computed Tomography

The composite rod composed of magnesium alloy wire and poly(lactic acid) (Mg wire/PLA) was prepared by hot-pressed process. The internal morphology evolution of the composites during degradation was investigated by x-ray computed tomography (XCT). Particularly, the location, amount, size, as well as sphericity of defects were visualized on the basis of XCT three-dimensional imaging technology and VGDefX algorithm. The result denoted that cracks were prone to appear near the outside location of the composites. The diameter-sphericity and volume-sphericity of defects inside the composites significantly increased after 6 weeks immersion. The alkaline degradation products in composite rods induced by the degradation of magnesium would promote the degradation of PLA and further accelerate the mechanical properties loss. Reasons for the inhomogeneity of degradation morphology were analyzed from the view of Mg wire, PLA matrix, as well as interface bonding state. Furthermore, the relationship between the evolution of degradation morphology and the attenuation of mechanical properties of the composites was presented. It is of great significance to provide theoretical guidance and method reference for in situ investigating the degradation performances of this kind of composites.