Development and optimised manufacturing of a tennis racket with novel carbon thin ply thermoplastic composites
Bhudolia, Somen Kumar
Date of Issue2018
School of Mechanical and Aerospace Engineering
The present thesis provides detailed investigation on development, manufacturing optimisation and characterisation of a novel composite material system using thin C-plyTM non-crimp carbon fabric (NCCF) of carbon in conjunction with Elium® resin (liquid thermoplastic resin) for its potential application as a material system for a tennis racket. First the, Vacuum Assisted Resin Infusion (VARI) process is optimised to manufacture the laminates for characterising the mechanical properties of the material system which are pivotal for a sporting racket. The comparative experimental characterisation study is carried out for thick plies vs. thin plies composites to understand the effect of reinforcement and, Thermoplastic, TP (Elium®) vs. Thermoset, TS (Epolam 5015) resin to demonstrate the benefits of newly developed thermoplastic resin. Furthermore, the Bladder Resin Transfer Moulding (B-RTM) process is proposed and optimised to be used as an alternative to costly prepreg process for mass production of a tennis racket The literature lacks the study on the liquid processing of thin ply NCCFs with room temperature cure Thermoplastic (TP)/Thermoset (TS) matrices. VARI process parameters like polymer flow rate, vacuum level, infusion temperature and time are optimised for the current material system under investigation. It was noticed that apart from the process parameters, material parameters like reinforcement’s permeability, polymer viscosity, type of flow mesh and peel ply also play a crucial role in VARI process and quality optimisation. After several iterations, usage of the 3 stage vacuum levels (500 mbar for infusion on the flow mesh, 400 mbar from the end of flow mesh until the infusion, and finally 330 mbar for consolidation) was found to be an optimum solution for infusing thin plies with TP and TS matrices. The advantages of both the thin plies as reinforcement and Elium® as the matrix system are studied. The thin ply laminates have shown higher tensile, flexural and interlaminar shear performance compares to the thick ply laminates and the underlying reasons for the same are deliberated by understanding the failure mechanisms. Thick NCCF Elium® composites have around 30% lower Mode I fracture value compared to thin ply variant. Structural Vibration tests demonstrated that the higher damping ratio for thin ply composites was mainly due to the increased stiffness and the number of interfaces. Higher peak load was noticed for Thin NCCF Elium® composite compared to Thick NCCF Elium® composites at 25 J, 42 J and 52 J impact events respectively. Also, the lower residual deflection and the higher major damage energy were noticed for Thin ply laminates compared to Thick ply laminates. Elium® composites shown 72.4 % increase in the critical energy release rate during the Mode I fracture toughness compared to epoxy composites due to the strong fibre matrix bonding as well as the global matrix plastic deformation which toughened the composite system. The damping at the glass transition temperature for Elium® composite was found to be 74 % higher than the epoxy composite system because of the larger transition region available for Elium® composite which consequently leads to higher energy dissipation. At higher impact energy levels of 42 J and 52 J, there is comparatively more gradual load reduction in case of Thin NCCF Epoxy composite laminates compared to the Elium® composites. PDm was higher in the case of Thin NCCF Elium® composite due to the higher elastic deflection offered until the ultimate load. This shows the tendency of the thermoplastic Elium® matrix to deform even before the ultimate load is reached. Higher major damage energy (Ebml) for Thin NCCF Elium® composite indicated the significant energy absorption before the onset of major failure mostly through elastic-plastic deformations.