Shuting Liu

Bio: Shuting Liu is an academic researcher from Nanjing University of Aeronautics and Astronautics. The author has contributed to research in topics: Curing (chemistry) & Composite material. The author has an hindex of 4, co-authored 10 publications receiving 395 citations.

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.

Micro-flow sensor for continuous resin fluidity monitoring between fibers

Abstract: The resin micro-flow between fibers influences bubble evacuation and fiber impregnation during the processing of fiber reinforced polymer (FRP) composites. The trapped bubbles and unimpregnated regions within a laminate will develop into voids after the processing, which will impair the structural performance severely. In this study, a new sensing principle of the step-changing difference of capillary pressure was proposed for the micro-flow measurement between reinforced fibers in FRP composites. A highly sensitive and calibration-free micro-flow sensor was designed by simply introducing an optical fiber with super-infiltration polyimide coating along the reinforced fibers. The FRP composite around the optical fiber was regarded as part of the sensing structure. The key resin flow states between fibers were first detected continuously during composite processing.

Fused filament fabrication of fiber-reinforced polymers: A review

Abstract: Recent advancements in the Additive Manufacturing (AM) Fused Filament Fabrication (FFF) approach are described with focus on the application to tooling and molds for composite materials and structures. A detailed summary of mechanical properties of printed parts for different composite material systems is presented and discussed. These material systems are comprised of discontinuous fiber-reinforced polymers characterized by fiber orientation dominantly parallel to the direction of the extrudate. An overview of the FFF process and its physical phenomena is given including the flow and resulting fiber orientation, the bond formation between adjacent beads and the thermomechanical solidification behavior of the deposited material. Based on reviewed research in these different phenomena, future research needs are discussed and desirable objectives are formulated.

Experimental characterization and micrography of 3D printed PLA and PLA reinforced with short carbon fibers

Abstract: The objective of this work is the mechanical characterization of materials produced by 3D printing based on fused filament fabrication (FFF, analogous to FDM ® ). The materials chosen are a polylactic acid (PLA) and a PLA reinforced with short carbon fibers in a weight fraction of 15 % (PLA+CF). In view of the FFF nature, which produces specimens layer by layer and following predefined orientations, the main assumption considered is that the materials behave like laminates formed by orthotropic layers. If the 3D printing is made in the 1 − 2 plane, where 1 is the deposition direction and 2 is a direction perpendicular to 1, the mechanical properties obtained are the tensile moduli E 1 and E 2 , the Poisson ratios ν 12 and ν 21 , the shear modulus G 12 and related strength properties. For this purpose, only unidirectional or specially oriented specimens are used. After tests up to material failure, scanning electron microscopy (SEM) is employed to observe fracture surfaces. It was noticed that, in the microstructure of the PLA+CF, the short carbon fibers stay highly oriented with the material deposition direction in the FFF specimens. This fact, and the also observed length of the fibers, explains differences in material properties encountered among the performed experiments.

FDM-Based 3D Printing of Polymer and Associated Composite: A Review on Mechanical Properties, Defects and Treatments.

Abstract: Fused deposition modelling (FDM) is one of the fastest-growing additive manufacturing methods used in printing fibre-reinforced composites (FRC). The performances of the resulting printed parts are limited compared to those by other manufacturing methods due to their inherent defects. Hence, the effort to develop treatment methods to overcome these drawbacks has accelerated during the past few years. The main focus of this study is to review the impact of those defects on the mechanical performance of FRC and therefore to discuss the available treatment methods to eliminate or minimize them in order to enhance the functional properties of the printed parts. As FRC is a combination of polymer matrix material and continuous or short reinforcing fibres, this review will thoroughly discuss both thermoplastic polymers and FRCs printed via FDM technology, including the effect of printing parameters such as layer thickness, infill pattern, raster angle and fibre orientation. The most common defects on printed parts, in particular, the void formation, surface roughness and poor bonding between fibre and matrix, are explored. An inclusive discussion on the effectiveness of chemical, laser, heat and ultrasound treatments to minimize these drawbacks is provided by this review.