Abstract
Within the dry fibre placement (DFP) process, spread and pre-bindered carbon fibre rovings are automatically processed into dry textile preforms using 2-D and 3-D laying systems. The aim was to automate existing hand lay-up processes, reducing the complexity, increasing robustness, and facilitating the handling of the DFP technology. Process reliability, low waste rates, and flexible production are demonstrated. In this publication, the influences of the process parameters, 2 mm wide gaps and the percentage of 90° plies in the laminate, are investigated with regard to the mechanical properties, the permeability, and the infusion times in the preform z-direction (thickness). The effects on stiffness and strength are compared for several use cases. An approach to determine the infusion times as a function of the laminate thickness, the ply structure, and 2 mm wide gaps is demonstrated and analysed using vacuum-assisted process (VAP) infusion tests. The investigations are performed with carbon fibre tows (24 k), a reactive epoxy-based binder system, and a thermoset infusion resin system.
Highlights
The values are separated into the two configurations of no gap and a 2 mm gap
The results show that the 2 mm gaps had no influence on the flexural modulus of the tested samples
The tensile strength was reduced by 7% when 2-mm-wide gaps were introduced
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. If the fibres are first combined with the matrix and moulded into shape, this is called a prepreg process. If the dry fibres are first shaped into a so-called preform and impregnated with a matrix system, it is called the preforming process. One of the preforming processes is a dry fibre placement (DFP) process called crosslayer. The production of fibre composite structures from spread dry carbon fibre tows, so-called fixed tows [1], is pursued with the aim of producing homogeneous laminates with a minimum of defects. The FAW of a single ply is adjusted by the spreading width of the tows and the web spacing. According to Gardiner [3], 80% of the carbon fibres are currently spread before processing. Bindered and spread fibres can be placed in any orientation within a single ply. The scope of this research is an evaluation the DFP process chain in combination with a simple state of the art liquid resin infusion method (VAP)
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