Effect of annealing treatment on mechanical properties of 3D-Printed composites

This study aims to analyse the annealing effect on the mechanical properties of PETG, carbon fibre reinforced PETG (PETG + CF) and Kevlar fibre reinforced PETG (PETG + KF). Regardless of the material, the final dimensions vary with temperature and exposure time, showing that the addition of fibres had no significant influence. On the other hand, the presence of fibres affects the radius of curvature, but this parameter shows to be very dependent on the type of fibre. In terms of hardness, higher temperatures and exposure times generally lead to higher values, achieving improvements of about 20% over untreated material. Regarding the bending properties, while they increase with exposure time and temperature for composites, in the case of neat PETG they increase with temperature and decrease with exposure time. Compared to untreated specimens, the maximum bending strength observed after the annealing treatment was 10.2%, 31.8% and 11.1% for PETG, PETG + CF and PETG + KF, respectively, while the maximum bending modulus was 17.6%, 61.1% and 62.6% higher, respectively. Benefits were also observed in terms of impact strength, stress relaxation and creep behaviour of all materials. For example, after annealing, lower stress relaxation and creep displacement values were observed.