Delamination formation, evaluation and suppression during drilling of composite laminates: A review

Carbon fibre reinforced polymer (CFRP) composites have excellent specific mechanical properties, these materials are therefore widely used in high-tech industries like the automobile and aerospace sectors. The mechanical machining of CFRP composites is often necessary to meet dimensional or assembly-related requirements; however, the machining of these materials is difficult. In an attempt to explore this issue, the main objective of the present paper is to review those advanced cutting tools and technologies that are used for drilling carbon fibre reinforced polymer composites. In this context, this paper gives a detailed review and discussion of the following: (i) the machinability of CFRP including chip removal mechanisms, cutting force, tool wear, surface roughness, delamination and the characteristics of uncut fibres; (ii) cutting tool requirements for CFRP machining; and (iii) recent industrial solutions: advanced edge geometries of cutting tools, coatings and technologies. In conclusion, it can be stated that advanced geometry cutting tools are often necessary in order to effectively and appropriately machine required quality features when working with CFRP composites.

Advanced cutting tools and technologies for drilling carbon fibre reinforced polymer (CFRP) composites: A review

Abstract Fiber-reinforced composites have become the preferred material in the fields of aviation and aerospace because of their high-strength performance in unit weight. The composite components are manufactured by near net-shape and only require finishing operations to achieve final dimensional and assembly tolerances. Milling and grinding arise as the preferred choices because of their precision processing. Nevertheless, given their laminated, anisotropic, and heterogeneous nature, these materials are considered difficult-to-machine. As undesirable results and challenging breakthroughs, the surface damage and integrity of these materials is a research hotspot with important engineering significance. This review summarizes an up-to-date progress of the damage formation mechanisms and suppression strategies in milling and grinding for the fiber-reinforced composites reported in the literature. First, the formation mechanisms of milling damage, including delamination, burr, and tear, are analyzed. Second, the grinding mechanisms, covering material removal mechanism, thermal mechanical behavior, surface integrity, and damage, are discussed. Third, suppression strategies are reviewed systematically from the aspects of advanced cutting tools and technologies, including ultrasonic vibration-assisted machining, cryogenic cooling, minimum quantity lubrication (MQL), and tool optimization design. Ultrasonic vibration shows the greatest advantage of restraining machining force, which can be reduced by approximately 60% compared with conventional machining. Cryogenic cooling is the most effective method to reduce temperature with a maximum reduction of approximately 60%. MQL shows its advantages in terms of reducing friction coefficient, force, temperature, and tool wear. Finally, research gaps and future exploration directions are prospected, giving researchers opportunity to deepen specific aspects and explore new area for achieving high precision surface machining of fiber-reinforced composites. 

https://link.springer.com/content/pdf/10.1007/s11465-022-0680-8.pdf

Fiber-reinforced composites in milling and grinding: machining bottlenecks and advanced strategies

/pdf/fiber-reinforced-composites-in-milling-and-grinding-fhcdm1c7.pdf

Damage formation and suppression in rotary ultrasonic machining of hard and brittle materials: A critical review

Rotary ultrasonic elliptical machining for side milling of CFRP: tool performance and surface integrity

Feasibility study of ultrasonic elliptical vibration-assisted reaming of carbon fiber reinforced plastics/titanium alloy stacks.

Disclosed is a high-effect and small-size rotary ultrasonic spindle. The high-effect and small-size rotary ultrasonic spindle is composed of an inner ring and outer ring flange-free needle bearing (1), a spring clamping ring (2), a rotary conductive sliding ring (3), an ultrasonic spindle body (4), a ceramic pile (5), a rear cover plate (6), a check ring (7), a deep groove ball bearing (8) and a spring clamping ring (9). The ultrasonic spindle body is supported by the bearings at the front end and the rear end to rotate, the inner ring and outer ring flange-free needle bearing (1) and the rotary conductive sliding ring (3) are arranged at the front end to achieve rotary power supply, the deep groove ball bearing (8) is arranged at the rear end, the ultrasonic spindle body is connected with a rotary spindle of a machine tool or a pneumatic tool in an external hexagon mode or an internal threaded hole mode to provide rotary power, the ceramic pile (5) and the rear cover plate (6) are arranged at the middle end, and a sleeve is adopted on the outer portion of the ultrasonic spindle body (4) for fixing. The high-effect and small-size rotary ultrasonic spindle is compact in structure, the size is minimized, the use range of a traditional machine tool and a pneumatic or electric rotary tool to materials hard to machine is widened, and machining cost is greatly lowered.

High-effect and small-size rotary ultrasonic spindle

The invention discloses a fast positioning device applied to an automatic feeding drill. The fast positioning device comprises a screw frame (4) used for being connected with an external screw device and providing feeding pushing force for the fast positioning device during working. A front section guiding assembly (2) is used for achieving the slight movement of a hole forming cutter in the axial direction. A rear section locking assembly (3) is used for achieving connection between a straight handle pneumatic drill body and the front section guiding assembly (2) and matched with the screw frame (4) through a universal bearing, it is guaranteed that the external screw device stably transmits the feeding pushing force to the hole forming cutter, the hole forming cutter is guided through the front section guiding assembly (2), and it is guaranteed that under the situation that the cutter is subjected to large axial force and torque, a pneumatic drill is prevented from playing and swinging in the axial center line direction, and the task of drilling laminated materials is smoothly finished. By means of cooperation of the front section guiding assembly (2) and the rear section locking assembly (3), the pneumatic drill carries out stable feeding in the drilling process, and cutter clamping does not exist.

Fast positioning device applied to automatic feeding drill

The invention discloses a high-precision ultrasonic dimple device for pneumatic drill. A transducer main shaft is connected with a hexagonal structure of a pneumatic drill handle in a matched mode through a rear end outer hexagon structure to transmit torque, and a rear cover plate and ceramic stack are connected to the transducer main shaft in a sleeving mode and press against a front cover platethrough the rear cover plate. A sliding ring inner ring is matched with the transducer main shaft through a flat structure and the sliding ring inner ring abuts against the transducer main shaft by afastening screw; one end of a sleeve is connected with the pneumatic drill handle through a left-hand thread, and the other end of the sleeve is matched with a depth-limiting positioning sleeve through a copper sleeve; the depth-limiting positioning sleeve is limited by a spring collar to ensure that the depth-limiting positioning sleeve can move within a limited distance; a dimple drill bit andthe transducer main shaft are connected in a threaded mode and positioned by a conical surface; and a flat bottom drill sleeve and the depth-limiting positioning sleeve are connected through threads to ensure that the high-precision ultrasonic dimple device is perpendicular to the machined surface during dimple machining. The high-precision ultrasonic dimple device can effectively prevent the problems that the cutting temperature is too high during common dimple machining and a tool is seriously worn, the verticality and surface flatness of a simple hole can be improved, and the high-precisionultrasonic dimple device has an important influence on the improvement of the stealth performance of an aircraft.

Liu Dapeng

Papers

Rotary ultrasonic elliptical machining for side milling of CFRP: tool performance and surface integrity

Feasibility study of ultrasonic elliptical vibration-assisted reaming of carbon fiber reinforced plastics/titanium alloy stacks.

High-effect and small-size rotary ultrasonic spindle

Fast positioning device applied to automatic feeding drill

High-precision ultrasonic dimple device for pneumatic drill