Sacrificial mandrels and micro-components made from pure aluminum have considerable application potential for fabricating terahertz micro-cavity components and for MEMS. Although WECMM has significant advantages in micro-shaping micro-components from difficult-to-machine materials, high-quality micro-shaping of pure aluminum has always been very challenging due to its extremely high chemical activity in an aqueous solution. This study analyzes the electrochemical characteristics of pure aluminum and the corresponding machining experiments by traditional WECMM in various electrolytes, and manufactures a high-quality micro-slit with a short machining path in the obtained ultra-low-concentration mixed electrolyte. However, in a continuous long-term WECMM with a long machining path, poor mass transport leads to the accumulation of bubbles around the machining area and the deposition of insoluble products on the wire surface that reduce the machining stability and machining accuracy. Therefore, a mass transport method of using intermittent ultrasonic oscillation is proposed. The principle was expounded, systematic comparative experiments demonstrated the effectiveness of this method in continuous long-time WECMM in improving the machining stability and machining accuracy. Finally, a rectangular mandrel of pure aluminum with a path length greater than 10,000 μm was fabricated. After dissolving the rectangular mandrel, a terahertz hollow-core rectangular waveguide micro-cavity was produced.

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The damage induced by lightning strikes in carbon-fiber-reinforced plastic (CFRP) laminates with fasteners is a complex multiphysics coupling process. To clarify the effects of different lightning current components on the induced damage, components C and D were used in simulated lightning strike tests. Ultrasonic C-scans and stereomicroscopy were used to evaluate the damage in the tested specimens. In addition, the electrothermal coupling theory was adopted to model the different effects of the arc and the current flowing through the laminate (hereinafter referred to as the conduction current) on CFRP laminates with fasteners under different lightning current components. Component C, which has a low current amplitude and a long duration, ablated and gasified the fastener and caused less damage to the CFRP laminate. Under component C, the heat produced by the arc played a leading role in damage generation. Component D, which has a high current amplitude and a short duration, caused serious surface and internal damage in the CFRP laminate and little damage to the fastener. Under component D, the damage was mainly caused by the Joule heat generated by the conduction current.

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