Investigation of shearing effects on the permeability of woven fabrics and implementation into LCM simulation

In liquid composite moulding (LCM) permeability is a key value for the process simulation. This value is dependent on many parameters such as fibre volume content, reinforcement architecture, and fibre type. When producing double curved parts the permeability of fabrics is additionally influenced by draping effects. The draping leads to a shearing of the fabric which decreases the permeability. This behaviour was investigated on a sample material consisting of four- and five-layer carbon fabric. The investigated fabric was increasingly sheared and the corresponding permeability was determined. It was found that the permeability decreases exponentially depending upon the fibre volume content of the fabric changed by shearing. Additionally the main axes of the permeability rotate. The rotation angle thereby is dependent on the absolute fibre volume content of the sheared material. This material behaviour was implemented into a commercially available LCM-simulation software which was verified first using a simple plate with a sheared fabric, then using a double curved structure (hemisphere) with draped fabric. The agreement of the simulation and the experimental results was excellent.