Fluid mechanics of slot-coating in photopolymer-based rapid composites manufacturing

Abstract

This paper describes the uid mechanics of the slot-coating process in the context of rapid layered manufacturing. It has been conjectured that slot-coating would successfully address a number of common dif culties encountered in the formation of thin layers from a highly viscous brephotopolymer composite liquid. The objective of the present study was therefore the development of an engineering analysis tool to assist with the design of a slot-coating-based liquid layer formation mechanism for use as an integral part of a lithography-based rapid layered composite parts manufacturing (R LCM) system.In addition to an analytical model, the paper presents a numerical model based on a volume-ofuid (VOF ) algorithm. This algorithm allows (a) solution of non-steady-state problems, (b) tracking of the free surface of the uid undergoing large deformations and (c) easy modi cation of the model's domain to facilitate experimentation with coater geometry. R esults from a set of simulated experiments establish a relationship between the liquid-coat height and several design and process parameters.Physical examination of cross-sections of several test parts built on an R LCM prototype system in the authors' laboratory con rmed the ability of the new coater design to form solid layers of good quality, as predicted by the numerical simulations.

Dynamic Capillary-Driven Additive Manufacturing of Continuous Carbon Fiber Composite

“…Techniques achieved by modifying popular automated composite manufacturing approaches such as tape layup and fiber placement/winding have been introduced to fabricate structural composites, 22,23 but these methods require special thermosetting resins for processing as well as post-heat treatment Article and the use of supporting structures in the process. Most 3D-printed composite work has been based on existing AM techniques, such as fused filament fabrication (FFF), [24][25][26][27][28][29][30][31] direct writing (DW), 32,33 vat photopolymerization (SLA), [34][35][36][37] powder bed fusion (PBF), 38,39 and sheet lamination process (SLP), 1 and the use of short fibers to reinforce thermoplastic polymers such as polylactic acid, acrylonitrile butadiene styrene, polyamide, and polyethylene, as well as UV-curable polymers (Table S3). Due to the low polymer service temperature, low fiber fraction, and low mechanical properties, these 3D-printed composites are inadequate to meet practical requirements.…”

Process-structure-properties of additively manufactured continuous carbon fiber reinforced thermoplastic composite

“…Additives may be added into the composite for various reasons, namely to facilitate polymerization, reduce the viscosity of the resin, stabilize the suspension, and to act as a coupling agent between the fiber and matrix. In another variation, a new layer of composite resin is added onto the build tray at the start of each layer to avoid sedimentation of fiber in the resin [99][100][101][102][103]. The fiber surfaces are treated in order to decrease the viscosity of resin to permit higher fiber concentration.…”