Novel Experimental-Simulative Approach for Permeability Determination of Textile-Reinforced Composites

Due to their outstanding properties, fiber reinforced polymers (FRP) are increasingly used in industries such as automotive industry, aviation industry, and also in the medical sector. Thereby, the heterogeneous structure of the FRP is the key to the excellent mechanical performance and the lightweight potential. Combined in an FKV, the material partners can bear loads that would destroy the individual components. In this context textile reinforced polymers show a better performance compared to short or long fiber reinforced polymers, but also go together with a structure which is even more complex. The structure of textile-reinforced FRP leads to manufacturing problems throughout the entire process chain, only to be addressed with considerable experimental efforts. Liquid Composite Molding (LCM) processes are suitable for fast and economical mass production of shell-shaped components of the industries mentioned. During an LCM process, dry preforms are impregnated with a low-viscosity thermoset resin. For an efficient process design, the permeability of textile reinforcement has a high relevance. Permeability describes the flow conductance of porous structures, in this case for textiles. A large amount of complex experiments must be carried out for each material and structure variation to determine the permeability. Moreover, there are no standards for permeability measurements and therefore no comparability is guaranteed.
Consequently, the main goal of the Math2Composites project is the development of a software module to support the design of parts and processes for textile-reinforced FRP. This new software module is based on a novel simulative-experimental approach for the determination of material properties like the permeability and is intended to replace a large share of experiments by validated simulations at key points (see Figure 1). The crucial point is the digital textile model, which is to be created by the new software module and calibrated using a small number of defined experimental tests. The time required for model creation and multiple simulations can be reduced to a minimum by using Python scripts and is less than the experimental permeability determination. In this context, the crucial factor is to consider critical textile variations, which have an influence on permeability, like ondulation, nesting, shearing, and deformation of roving in the digital textile model with justifiable effort. Furthermore, a multiscale approach is selected for the simulation (see Figure 2) in order to minimize the computing time. To determine the permeability of a textile, the permeability of the rovings is first determined by simulation. Thus, the rovings can then be represented in the textile model as porous solid material strands with the previously determined permeability. The aim of the simulative-experimental approach is to obtain a range of values that represents the standard deviation of the experimental determined permeability caused by the variations of the textiles. With sufficiently large randomized models, which represent real material structures in sufficiently large models, a comparable variance to the experiments is to be expected. With the successful development of the simulation tool, the time and financial effort for extensive permeability determination and process design can be reduced and thus promote new applications of FRP parts. For this purpose, IVW cooperates with Math2Market GmbH, who has developed GeoDict, the digital material laboratory software.

The project Math2Composites („Material simulator for design and manufacturing of textile reinforced composites – development of an integrated simulative-experimental characterization of fiber reinforced polymers“) is funded by the Federal Ministry of Economic Affairs and Energy (BMWi) within the ZIM program (funding reference: ZF4052310EB6).

Further Information:
M.Sc. Tim Schmidt
Manufacturing Science
Institut für Verbundwerkstoffe GmbH
Erwin-Schrödinger-Str. 58
67663 Kaiserslautern
Telephone: +49 (0) 631/31607 32
E-Mail: tim.schmidt@ivw.uni-kl.de