Comparative Analysis on Low Cost Continuous Carbon Fiber Polypropylene Composite Using Compression Molding and Automated Tape Placement

Carbon fiber reinforced plastics (CFRP) are widely used throughout the aerospace industry where a weight reduction remains the highest priority with less emphasis on cost. Textile grade carbon fiber (TCF) and other low cost carbon fiber (LCCF) alternatives have recently emerged for use in the automotive market where emissions regulations have pushed automotive manufacturers and research institutions to look for cost effective light weight materials. Fiber reinforced thermoplastics provide an effective solution that align with automotive design including low cost, high processing rates, high impact toughness, unlimited shelf life, and recyclability. TCF and Zoltek_PX35 fibers are two LCCF aimed at the automotive, wind energy and commercial markets that are helping to push the cost of CF down to approximately $5 per lb. In combination with a hot melt thermoplastic pultrusion impregnation technique, an intermediate low cost composite tape can be produced that is shown to have good mechanical performance when consolidated through hot compression molding (CM). Automation is critical to the required rapid part production and process control within the automotive industry. Research was conducted into the manufacturing process parameters of LCCF composite tapes through in-situ consolidation with an automated tape placement (ATP) or automated fiber placement (AFP) robotic system. This research focuses on the manufacturing of low-cost continuous polypropylene composites and explores the mechanical and morphological properties associated with compression molding and automated tape placement

Automated Fibre Placement with In-Situ Ultraviolet Curing and On-The-Fly Resin Impregnation

Vehicle emissions contribute to up to one third of the world's air pollution [1]. Reducing vehicle weight is crucial to reducing these emissions. Composite materials offer high specific strength-to-weight ratios which make them ideal for lightweight applications; however, existing composite manufacturing is slow and expensive. Automated Fibre Placement (AFP) is a state-of-the-art composite manufacturing process but is limited by the low complexity of parts it can produce; the cost, size and speed of the actuation systems; expensive and sensitive material options; and numerous pre and post-processes required in order to complete a part. This research proposes a new and efficient composite manufacturing process that addresses these limitations by combining AFP technology with in-situ ultraviolet (UV) curing and on-the-fly fibre and resin impregnation (UVAFP). The body of this thesis focused on proving the process concept and building robust predictive models for the technology. It was proposed that reducing the size of the placement head would increase the capability of this technique to manufacture more complex parts. It was shown that by optimising the placement head clearance angle, placement head width and the compaction roller radius the minimum placement radius and arc length could be as small as 100mm and 90 degrees respectively. It was also demonstrated that industrial robots were sufficiently accurate and repeatable to act as placement articulators for AFP. The feed rate, path interpolation point filtering and spindle speed were optimised to achieve a path following accuracy of less than 0.042mm. By increasing the tension in the tow and compaction force, dry fibre tows were shown to be a suitably dimensionally stable replacement for expensive towpregs with minimal gaps and overlaps. Dry glass fibre tows and bulk vinylester resin impregnated on-the-fly was chosen as an inexpensive and versatile material system and consolidation approach for use in UVAFP. The material system was shown to have comparable mechanical properties to aluminium and steel but lighter with equivalent properties to composites manufactured by traditional techniques. Rapid impregnation times were demonstrated up to 2160 mm/sec. High intensity UV light curing eliminated the need for post process curing and shortened the cure time and increased layup speeds. When the UV light was applied in a ply-by-ply in-situ approach, the cure time was measured to decrease the current thermal cure cycle length by 43.75% and the degree-of-cure was increased by 1.3% (as measured indirectly by the interlaminar shear strength). By characterising the process parameters the effect on degree of cure and degradation could be controlled and predicted. A degree of cure in excess of 99% was achieved, providing equivalent material properties to traditional thermal cured composites while minimising peak exposure temperatures, thus reducing mass loss caused by thermo-oxidative degradation. UVAFP was demonstrated to be a viable composite manufacturing process capable of producing high quality components and addressing the limitations of current AFP systems. The technology was shown to address efficiency shortfalls and make composite manufacturing economical and accessible to vehicle manufacturers searching for manufacturing process solutions for lightweight

The influence of consolidation force on the performance of AFP manufactured laminates

With the increasing use of carbon/glass fibre reinforced polymer composites for large components like wing skins, fuselages and fuel tanks in aircrafts and next generation of spacecraft, utilization of advanced automated manufacturing is critical for mass production. In-situ consolidation in automated fibre placement (AFP) technology through merging several manufacturing stages like cutting, curing and consolidation has opened up a wider range of applications as well as new markets for composite materials in several sectors including aerospace and automobile in large scale. Nevertheless, the quality and integrity of AFP manufactured composites is heavily dependent on large number of variables and parameters like lay-up speed, curing/melting temperature and consolidation force. In order to establish and understand a correlation between the key parameters in AFP and the mechanical properties, several parametric experiments were performed. This is done through manufacturing uni-directional carbon fibre reinforced polymer laminates and identifying some of their main mechanical properties at different location along the length of samples. It was found that, the strength of laminates at different locations is critically dependent on the effect of those parameters

Selectively embedding multiple spatially steered fibers in polymer composite parts made using vat photopolymerization

Fiber-Reinforced Polymer Composite (FRPC) parts are mostly made as laminates, shells, or surfaces wound with 2D fiber patterns even after the emergence of additive manufacturing. Making FRPC parts with embedded continuous fibers in 3D is not reported previously even though topology optimization shows that such designs are optimal. Earlier attempts in 3D fiber reinforcement have demonstrated additively manufactured parts with channels into which fibers are inserted. In this paper, we present 3D printing techniques along with a printer developed for printing parts with continuous fibers that are spatially embedded inside the matrix using a variant of vat photopolymerization. Multiple continuous fibers are gradually steered as the part is built layer upon layer instead of placing them inside channels made in the part. We show examples of spatial fiber patterns and geometries built using the 3D printing techniques developed in this work. We also test the parts for strength and illustrate the importance of spatially embedding fibers in specific patterns.Comment: 9 pages and 8 figure

Additive Manufacturing for Nautical Design An Automated Approach to Marine Manufacturing

How can additive manufacturing (AM) technology be applied to automate the production of small marine vessels? For the past 50 years small (below 40 meters) marine vessel manufacturing has been dominated by moulded fiber-reinforced plastics (FRP). There are several shortcomings to this manufacturing method that affect both the formal outcome and the manufacturing process of boats built in FRP: 1) manufacturing requires the use of expensive moulds, 2) formal geometric freedom is limited by moulds which reduce the potential for customization, and 3) special assemblies and structural reinforcements must be moulded separately and joined using a time-consuming hand lay-up process. The use of AM may reduce cost of production by eliminating need for moulds, allow greater ease of customization, and improve worker safety by limiting exposure to harmful materials and chemicals. The purpose of this research project is to evaluate existing AM technology and assess its potential for application to small marine vessel manufacturing. The project aims to investigate new methods for generating novel AM tool paths and demonstrate through proof of concept that it may be possible to produce the complex topological surfaces and assemblies that are common in marine vessels using multi-bias additive manufacturing (MBAM). However, AM is a broad term that describes a variety of different ways to manufacture objects. As such, AM can be applied to marine manufacturing in a variety of different ways, in different phases of the manufacturing process, and to different extents. At the same time, building boats is a complex process that presents specific problems that must be addressed in any automation solution. Several marine vessel construction projects have already been completed using AM which can serve as case studies for understanding the opportunities and challenges for applying AM to the marine sector. A review of the current state of the technology and qualitative analysis (QA) of case studies provides a set of guidelines for designing a manufacturing method that may prove effective for producing small marine vessels using AM. The project relied on design-based research (DBR) to develop a series of experimental extruder prototypes for novel toolpath testing on excerpts from a small reference vessel. The combination of QA and DBR experimentation point to a manufacturing solution using articulated robotic manipulators and a continuous fiber thermoset plastic extruder using a modified version of the fused filament fabrication process. This kinematic solution can be extended with external linear or rotational axes and/or by mounting robotic manipulators within a large gantry. This will allow the extruder to approach the work using a wide range of orientations that will be optimal for both the geometry of marine vessels and the requirements of MBAM extrusion. Meanwhile, toolpath generation using the software Grasshopper with KukaPRC plugin demonstrated a proof of concept for creating MBAM toolpaths optimized for small marine vessels. While the method proved feasible for smaller excerpts there remain significant challenges to successful deployment of this manufacturing method that can only be addressed with additional research