Novel Experimental Unit to Evaluate Inter-ply and Tool-Ply Friction in Carbon Fibre Reinforced Polymer Composites Prepregs

There exist many challenges in the design and manufacture of complex geometries using carbon fiber reinforced composite prepregs. Frictional phenomena occur between the tool and the heated laminate and between subsequent prepreg plies within a laminate during forming stage of composite parts. The constrains imposed by friction during forming operations may generates major defects, which then transfer into the final component. As a result, characterization of tool/ply and ply/ply friction during composite forming is relevant to achieve process optimization along with high manufacturing quality. Since there is no ASTM standardized procedure available for frictional measurement of composites, most tests are based on different custom built fixtures. A dedicated experimental unit has been designed and constructed at Montana State University for inter-ply and tool-ply frictional characterization of continuous and stretch broken carbon fiber (SBCF) composite prepregs. The unit based on a pull-through test approach, is designed to be fitted in a universal testing machine. The proposed novel testing unit allows for the evaluation of frictional forces by simulating forming process parameters that composite material encounters during forming operation such as temperature, forming rate, normal pressure and ply orientation. Preliminary results from friction experiments using commercial continuous prepreg materials are presented and compared.