Jing Zhou

Bio: Jing Zhou is an academic researcher from Nanjing University of Aeronautics and Astronautics. The author has contributed to research in topics: Curing (chemistry) & Microwave. The author has an hindex of 8, co-authored 20 publications receiving 208 citations.

Drilling delamination and thermal damage of carbon nanotube/carbon fiber reinforced epoxy composites processed by microwave curing

Abstract: The drilling-induced delamination and thermal damage of carbon fiber reinforced epoxy composite materials are serious problems especially for high value components of the aviation industry. To suppress the delamination and drilling ablation, an innovative approach was employed in this study. The multiwalled carbon nanotubes (MWCNTs) were introduced to the matrix resin to improve the interlaminar strength and thermal conductivity. The as-prepared composite was processed by microwave curing to enhance the interface strength between carbon fiber and the carbon nanotubes modified matrix. During the drilling processes, optical fiber Bragg grating sensors were utilized to precisely measure the drilling temperature. Experimental results indicated that the interlaminar fracture toughness was increased by more than 66% compared to that of the traditional thermal cured samples without MWCNTs. And the delamination factor was decreased by 16% according to the computerized tomography scanning results. The maximum drilling temperature of the MWCNTs reinforced composite was below the glass transition temperature of the matrix resin and declined by 23 °C compared to traditional composites. With this novel method of carbon nanotube modification and microwave curing, we provide the capability of reducing the drilling delamination and thermal damage of carbon fiber composites simultaneously, and explored the possibility of manufacturing and machining integration.

Curing multidirectional carbon fiber reinforced polymer composites with indirect microwave heating

Abstract: Microwave curing technologies have many advantages in manufacturing fiber reinforced polymer composite materials used in aerospace products, compared with traditional autoclave curing technologies. However, multidirectional carbon fiber reinforced polymer composites can hardly be penetrated and heated by microwave directly, which has become a major obstacle in industrial application worldwide. In this paper, an indirect microwave curing method was proposed to solve this problem. The microwave absorption performance of the indirect microwave heating medium was systematically optimized by evaluating its dielectric properties and reflection loss according to the transmission line theory. On this basis, the microwave susceptive mold was carefully designed and manufactured. Subsequently, the multidirectional carbon fiber/epoxy composite was successfully cured with indirect microwave heating, which was demonstrated by the observation of the curing process with infrared thermal imager and differential scanning calorimetry analysis of the final products. Compared with the traditional thermal curing method, the curing cycle and energy consumption were reduced by 42.1% and 75.9% respectively. Results of further characterization experiments indicated that the mechanical properties of indirect microwave cured specimens were slightly higher than those of the thermally cured counterparts.

A multi-pattern compensation method to ensure even temperature in composite materials during microwave curing process

Abstract: Microwave curing technologies have many advantages in manufacturing fiber reinforced polymer composite materials used in aerospace products, compared with traditional autoclave curing technologies. However, the uneven electromagnetic field of microwave in the cavity of the curing chamber results in uneven temperature on the surface of composite laminates during curing, which has been a major obstacle in industrial applications worldwide. Existing methods attempted to solve the problem by the random superposition of uneven electromagnetic fields, but the results were still not satisfactory to meet the high quality requirements of aerospace parts. This paper reveals the one-to-one correspondence between heating patterns of composite parts and microwave curing system settings, and reports a new concept to solve this problem by continuously monitoring and compensating the uneven temperature distribution in real-time. Experimental results from both fiber optical fluorescence sensors and infrared thermal imagers showed significant improvement in temperature uniformity compared with existing methods.

Composites Part A: Applied Science and Manufacturing

Abstract: Reference EPFL-ARTICLE-184271doi:10.1016/j.compositesa.2012.08.001View record in Web of Science Record created on 2013-02-27, modified on 2017-05-10

A review of helical milling process

Abstract: Helical milling is an alternative hole-making machining process which presents several advantages when compared to conventional drilling. In the helical milling process, the tool proceeds a helical path while rotates around its own axis. Due to its flexible kinematics, low cutting forces, tool wear, and improved borehole quality may be achieved. This paper presents a review of the helical milling process. As a first paper aiming to describe the current state of the art of helical milling process, the recent works about this process were summarized to point out the future trends in this field. Initially, the advantages of the helical milling were presented with regard to conventional drilling. Subsequently, the kinematics of the process was presented to standardize the nomenclature and to provide knowledge about the movements and parameters of helical milling. It was demonstrated the feed velocity decomposition in frontal and peripheral directions. Undeformed chip and cutting volumes of frontal and peripheral cut were described, and the ratio between the cutting volumes removed by frontal and peripheral cut was demonstrated to be dependent only of the borehole and tool diameters. Cutting forces and temperature studies were also summarized, corroborating that the helical milling is a smooth hole-making process. Afterward, tool life and wear studies in helical milling were summarized, testifying that the tool wear evolution can be monitored in frontal and peripheral cutting edges, with frontal cutting edges, in most cases, defining the tool life. Some statistical and soft computing applications on helical milling were also mentioned. To provide initial guidelines for applying helical milling, a screening of the current literature was performed summarizing equipment and cooling techniques used, and the levels of cutting conditions of helical milling applied for hole-making different materials. The quality of boreholes obtained by helical milling was assessed in terms of dimensional, geometrical, and microgeometrical deviations, besides burr and delamination levels, assuring that it can be obtained finished boreholes with helical milling. In the conclusions, future possibilities on research about helical milling were pointed out. This general review of helical milling may be referenced as a summary of the current results obtained in experimental and theoretical studies and to provide future research needs and opportunities.

Occurrence and formation mechanism of surface cavity defects during orthogonal milling of CFRP laminates

Abstract: Carbon fiber reinforced polymer (CFRP) has been commonly used in the aviation industry and related machining demands are increasing. During machining CFRP, severe machining defects, such as delamination, burrs and subsurface damages etc., usually occur due to the prominent anisotropy and heterogeneity of CFRP. Surface cavity defects are a major manifestation of subsurface damages leading to the decline of the machined surface quality. This paper aims to investigate the occurrence and formation mechanism of the surface cavity defects in a continuum of fiber cutting angles ( θ ) ranging from 0°–180° by circular orthogonal milling of unidirectional CFRP laminate disks. The experimental results showed that the surface cavities only occur on 50–60% of the against fiber cutting region (0° θ