PSI - Issue 56

Tamas Krausz et al. / Procedia Structural Integrity 56 (2024) 71–77 Krausz/ Structural Integrity Procedia 00 (2019) 000–000

74

4

Figure 2 shows the engineering stress-strain response in monotonic tension of the neat and fiber reinforced polycarbonate grades as function of three different temperatures (22 ° C, 40 ° C, 80 ° C). The curves for the individual materials are having the same shape, differentiated by the shifts caused by the temperature conditions. These reflect an elastoplastic behavior which consists of a viscoelastic region followed by the yield point (considered as the local maximum point on the stress-strain curve), then by the plastic or flow region and concludes with the end point where the material failure occurs. Similar nonlinear material deformation tendency under quasi-static monotonic tension conditions is described by several studies in the literatures (Krausz et al., 2021), (Autade & Pawar, 2015). In case of the MK8035, however, the curves are only characterized by non-linear elasticity, as due to the brittleness of the material this will fail without any significant softening after reaching the maximum stress value that the material can still withstand, independent of the temperature variations. One common observation for all the studied material grades is the yield stress showing a strong temperature dependency.

0 20 40 60 80

0 20 40 60 80

(a)

(b)

22C 40C 80C

22C 40C 80C

Stress [MPa]

Stress [MPa]

0 20 40 60

0 20 40 60

Strain [%]

Strain [%]

0 20 40 60 80

(c)

22C 40C 80C

Stress [MPa]

0 1 2 3

Strain [%]

Fig. 2. Force-deflection curves as function of temperature of the three polycarbonate grades: (a) MK2405, (b) MK9415 and (c) MK8035.

Table 1 summarizes the average and standard deviation values of the elastic modulus of the materials in terms of the three temperature levels that have been selected for the study. Like the flow stress, the elastic modulus is also highly influenced by temperature. This undergoes a decrease of up to 13% for the MK2405 and for the MK9415, and a slightly lower decrease of 7.5% for the MK8035.