Dalian University of Technology

Yu Bai

Fuji Wang

Wei Liu

Zhenyuan Jia

Jianwei Ma

Rao Fu

Meng Zhao

Boyu Zhang

Bin Niu

Chunling He

De Cheng

Chong Zhang

Jiaxuan Hao

Zegang Wang

The present invention belongs to the technical field of machining of fiber-reinforced composites, and relates to a method for measuring distribution of a thrust force during drilling of a unidirectional composite along with a fiber cutting angle. The method includes: cutting the surface a composite sample piece to form a groove; drilling on an existing experimental platform for measuring a thrust force during drilling, where a through hole obtained through the drilling is required to intersect with the groove; obtaining a curve of the thrust force during drilling, comparing the curve with a conventional curve of the thrust force to find a mutation point, and determining the mutation point, namely a fiber cutting angle at the groove; and calculating fluctuation periods of the thrust force according to machining parameters to reckon the distribution of the thrust force along with the fiber cutting angle in all the periods.

Method for measuring distribution of thrust force during drilling of unidirectional composite

A kind of sawtooth structure with reversed cutting function and its drill series are presented in this invention. This invention is suitable for drilling low-damage holes on carbon fiber reinforced polymers (CFRP). The sawtooth structure is comprised of sawteeth and grooves located on the cutting edges of drill. And the sawtooth structure is helically arranged with a specific helix angle around the axis of the drill. It can be classified as the left-hand helix sawtooth structure and the right-hand helix sawtooth structure based on the helix angle value. The bottom edges of the left-hand helix sawtooth structure are the cutting edges, and the rake angles are positive; while the top edges of the right-hand helix sawtooth are the cutting edge with the positive rake angles. The sawtooth structure can be applied to various drilling tools, which proves to be universal. And it can effectively reduce delamination at both hole entrance and hole exit as well as burrs defects. The series of drilling tools include the double point angle drill, the twist drill and the stepped drill all of which have the sawtooth structure on the cutting edges. These series of drilling tools can achieve the CFRP holes with minimum drilling defects. The drilling performance of the tools is improved to a great extent, the tool life is extended and the costs are reduced.

Sawtooth structure with reversed cutting function and its drill series

A vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and thereof hybrid stack structure, and has three parts which are a major cutting edge region A, a minor cutting edge region B and a shank region C. The minor cutting edge region B comprises a step vertical-edge region D and a sawtooth cutting region E. This has the step structure and the sawtooth structure which is distributed in the first step, has a recutting function at the inlet and a reverse cutting function at the outlet in the direction opposite to the main cutting motion. The cutter has the vertical edge structure distributed in the second step, and the angle of the second step is a negative value, thereby realizing chip breaking and crushing, reducing scratch to the upper-layer composite material and metal hole walls.

Vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and hybrid stack structure thereof

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Dalian, China

Yu Bai