Issue 47

J. P. Manaia et alii, Frattura ed Integrità Strutturale, 47 (2019) 82-103; DOI: 10.3221/IGF-ESIS.47.08 88 PA 6, HDPE and PP at three crosshead speeds are displayed in Figs. 5 and 6, for each specimen geometry. The load- displacement responses were compared to ensure repeatability of the results. The scatter between the tests batches was relatively small. Figure 5 : Tensile load-displacement curves of (1) flat notched R=5 and (2) flat notched R=30 specimens (PA 6, HDPE and PP at RT). Figure 6 : Tensile load-displacement curves of (1) cylindrical notched R=5 and (2) cylindrical notched R=30 specimens (PA 6, HDPE and PP at RT). Initially, the deformation is linear with the load increasing proportionally to the displacement. There is then a nonlinear region prior to yield load followed by yield, where the force reaches a maximum. It is observed that the yield load decreases with the reduction of testing speed and the corresponding displacement increases inversely. At higher crosshead speed, increases both the propensity of the material to form a clear and higher yield load at lower displacement values. At lower crosshead speeds, the polymer macromolecules have more time to induce an orderly alignment just enough to accept the increase in deformation. It is also clear the reduction of ductility as the crosshead speed increases exhibiting the material a more brittle behaviour. Higher crosshead speeds reduce the degree of chain relaxation, resulting in more preferred orientation [19]. The maximum/failure displacements achieved were for crosshead speeds of 1 mm/min. 0 1000 2000 3000 4000 5000 6000 7000 8000 0 2 4 6 8 10 12 Load, F (N) Displacement ,   V [mm] PA 6, HDPE and PP Room Temp. | Tensile Flat  Notched 5 | Testing Speeds 1, 20 and 200 (mm/min)  PA_FN_5_Testing Speed 200 PA_FN_5_Testing Speed 20 PA_FN_5_Testing Speed 1 HDPE_FN_5_Testing Speed 200 HDPE_FN_5_Testing Speed 20 HDPE_FN_5_Testing Speed 1 PP_FN_5_Testing Speed 200 PP_FN_5_Testing Speed 20 PP_FN_5_Testing Speed 1 0 1000 2000 3000 4000 5000 6000 7000 8000 0 2 4 6 8 10 12 Load, F (N) Displacement ,   V [mm] PA 6, HDPE and PP Room Temp. | Tensile Flat Notched 30 | Testing Speeds 1, 20 and 200  (mm/min)  PA_FN_30_Testing Speed 200 PA_FN_30_Testing Speed 20 PA_FN_30_Testing Speed 1 HDPE_FN_30_Testing Speed 200 HDPE_FN_30_Testing Speed 20 HDPE_FN_30_Testing Speed 1 PP_FN_30_Testing Speed 200 PP_FN_30_Testing Speed 20 PP_FN_30_Testing Speed 1 0 200 400 600 800 1000 1200 1400 1600 0 4 8 12 16 20 24 Load, F (N) Displacement ,   V [mm] PA 6, HDPE and PP Room Temp. | Tensile Cylindrical  Notched 5 | Testing Speeds 1, 20 and 200 (mm/min)  PA_CN_5_Testing Speed 200 PA_CN_5_Testing Speed 20 PA_CN_5_Testing Speed 1 HDPE_CN_5_Testing Speed 200 HDPE_CN_5_Testing Speed 20 HDPE_CN_5_Testing Speed 1 PP_CN_5_Testing Speed 200 PP_CN_5_Testing Speed 20 PP_CN_5_Testing Speed 1 0 200 400 600 800 1000 1200 1400 1600 0 4 8 12 16 20 24 Load, F (N) Displacement ,   V [mm] PA 6, HDPE and PP Room Temp. | Tensile Cylindrical  Notched 30 | Testing Speeds 1, 20 and 200  (mm/min)  PA_CN_30_Testing Speed 200 PA_CN_30_Testing Speed 20 PA_CN_30_Testing Speed 1 HDPE_CN_30_Testing Speed 200 HDPE_CN_30_Testing Speed 20 HDPE_CN_30_Testing Speed 1 PP_CN_30_Testing Speed 200 PP_CN_30_Testing Speed 20 PP_CN_30_Testing Speed 1 (2) (1) (2) (1)