Thermoplastic carbon fiber laminates can be drilled using ultra-fast feed methods in the future.
Aerospace and automotive manufacturing are two industries that best reflect industrial capabilities and the completeness of the supply chain in modern industrial fields, involving countless technologies and materials. Carbon fiber and composite materials are currently a very popular new type of material in industrial production, gaining favorable applications due to their outstanding mechanical properties. In practical applications, carbon fiber serves as a reinforcement material that can be combined with different matrix materials, allowing it to be processed into various shapes of industrial components, some of which can be applied in the aerospace and automotive manufacturing sectors.
Currently, mainstream thermosetting carbon fiber, as well as the more advantageous thermoplastic carbon fiber in the future, are considered to be high-performance composite materials that are difficult to surpass. However, processing these carbon fiber composites into finished products poses certain challenges, requiring the coordination of various equipment and machinery. Basic operations such as drilling, cutting, and hollowing are essential. Yet, one should not underestimate these basic processing steps, as the machining operations are also crucially linked to the performance of carbon fiber products. This article references international scholarly literature to introduce the ultra-fast feed drilling method and compares it with two other processing methods: ultrasonic vibration and abrasive water jet cutting.
Three Drilling Methods for Thermoplastic Carbon Fiber (CF/PA6) Laminates
1.Ultra-Fast Feed Drilling (UFFD): Cutting heat and friction heat can lead to the melting of the thermoplastic matrix, affecting drilling efficiency and results. To study the actual effects of the ultra-fast feed drilling method, the thermoplastic carbon fiber laminate is fixed, and feed speeds of 3000, 5000, and 7000 mm/min are selected, using a three-component dynamometer for measurement.
2.Ultrasonic Vibration Drilling (UVD): A piezoelectric crystal oscillator is installed on the equipment to provide a constant frequency of 70 kHz, allowing observation of the actual effects of ultrasonic vibration when drilling into thermoplastic carbon fiber laminates.
3.Abrasive Water Jet Drilling (AWJ): Abrasive water jet machining is currently the mainstream method for cutting thermosetting carbon fiber products. The water jet trajectory is designed in a circular shape, and a certain water pressure is applied to drill into the thermoplastic carbon fiber laminate, with the actual effects observed.
Demonstration of the Actual Effects of Ultra-Fast Feed Drilling
1.Comparison of Drilling Effects: When comparing a feed speed of 3000 mm/min with a low feed speed of 50 mm/min, the former achieves cutting completion more quickly, expelling only a small amount of chips, and leaving no burrs near the drilled hole. In contrast, the latter shows significant deformation when the drill bit penetrates the front laminate, with a larger amount of chip residue and crown-like burrs around the hole. The peak thrust at 3000 mm/min is six times that of 50 mm/min, reaching nearly 22N, while the drilling time is only 1/60 of the latter's, significantly increasing drilling efficiency and improving drilling quality.
2.Delamination and Burr Situation: Observations using a 3D measuring microscope reveal that delamination and burrs occur in relation to the drilling entrance direction, with 20 μm serving as the dividing line. When the feed speed is 3000 mm/min, no delamination is observed regardless of the spindle speed. However, when the feed speed exceeds 3000 mm/min and the spindle speed exceeds 20,000 min⁻¹, the volume of delamination increases with the rise in feed rate. This is attributed to the greater thrust generated at higher feed speeds.
Additionally, as the spindle speed increases, the volume of burrs that appear decreases. Through multiple experiments, it was found that at a feed speed of 3000 mm/min and a spindle speed of 20,000 min⁻¹, there is no delamination issue, while also maintaining a smaller burr volume. Overall, this results in better drilling performance.
3.Comparison with the Other Two Drilling Methods: To better compare the drilling effects, microscopic images of each drilling method were observed in the experiment. In the ultra-fast feed drilling (UFFD), each layer of carbon fiber is clearly visible on the hole wall, whereas in ultrasonic vibration drilling (UVD) and abrasive water jet drilling (AWJ), the hole walls are covered by a melted matrix, resulting in a more blurred surface. When the microscopic images are magnified, the AWJ hole walls show significant diffusion of nylon fibers, while the edges of the holes from UFFD exhibit better quality. Based on the comparison of hole surface quality, shape accuracy, and processing time, ultra-fast feed drilling (UFFD) proves to be a more promising drilling method for thermoplastic carbon fiber laminates.
Drilling holes in thermoplastic carbon fiber panels is a fundamental processing method, enabling stable connections with other industrial components and enhancing their commercial value. Currently, the widespread application of thermoplastic carbon fiber composites is still in its early stages, and the preparation of unidirectional thermoplastic carbon fiber composites poses significant challenges, which limits the application of these materials from the outset. As one of the few companies in China capable of independently producing continuous carbon fiber thermoplastic composite unidirectional tapes, Zhishang New Materials believes that the development of thermoplastic carbon fibers must start from a foundational level, and technological advancement is the primary condition to solve existing problems.
