PSI - Issue 42

F. Cesarano et al. / Procedia Structural Integrity 42 (2022) 1282–1290 F. Cesarano, M. Maurizi, C. Gao, F. Berto, F. Penta, C. Bertolin / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4a: Bi-layer specimens design (0° - 90°)

Fig. 4b: Reference specimen (bending deformation)

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Fig. 5a: First experimental method (from RT to 70°C, for 5 seconds)

Fig. 5b: Second experimental method (70°C, for 5 minutes)

In order to validate the experiments, simple simulations were carried out without implementing the viscoelastic behaviour and the SME of the PLA, since in order to be able to do so, dynamic mechanical analysis (DMA) should have been carried out [5]. The constitutive relationships characterizing the material should have been obtained, like in Scalet et al., 2015 [13], to implement a UMAT. Since this was preliminary research, this complex numerical modelling was out of the scope of the work. It was noted that by modelling a composite specimen identical to the reference one and inserting the orthotropic properties of the PLA described in Table 2, a slight bending in the XY plane was obtained by inserting gravitation and thermal loading; this suggests that the type of deformation is correct. Thus, considering a non-linear test given the high displacements, concentrated loads were inserted along Z-axis at the extreme nodes able to follow the rotation of the nodes; this allowed to obtain the same deformation as in the experiments and to estimate the magnitude of the residual stresses involved (Fig. 6, Fig. 7). More precisely, the modulus of was identified through trial and error to obtain the same max displacement. Notwithstanding, this procedure generated an error between the curvature of the simulated component and the real one due to the different x-coordinates to which the max displacement corresponded. These simulations help analyze the error between an experiment in which viscoelastic behaviour and SME are present and a linear simulation.

Fig. 6: FEA model - CompositeLayup 90° & 0°

Fig. 7: Generic FEA comparison (Max displacement)