PSI - Issue 35

S. YaŞayanlar et al. / Procedia Structural Integrity 35 (2022) 18– 24

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Yas¸ayanlar et al. / Structural Integrity Procedia 00 (2021) 000–000

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4.1. Uni-axial Tension Test

As the first example, uni-axial tension test conducted by dog-bone specimens to characterize epoxy, Fiedler et al. (2001) is considered by using the proposed hexahedra element. Tension-compression asymmetry in yield stress is observed in epoxy and its elasto-plastic response is well described by the compressible plasticity model introduced in the previous section, Melro (2013). Model parameters are given in Table 1 along with the parameters of the exponential damage law. Tensile and compressive yield stresses (yield stress versus equivalent plastic strain graphs) are extracted from Mororo and van der Meer (2020) and not reported here.

Table 1: Model Parameters

l2 CL

Model Parameter

Value

E

3760 MPa

0.39

ν

0.6 mm

l c κ i α

0.03 0.95 25.0

t

l1

β

R

0.005

Fig. 1: Geometry of dog bone specimen

5.0

η

Half of the specimen (see Figure 1 for the dimensions) is discretized with hexahedra elements and an initial im perfection is not introduced. Both conventional and localized implicit gradient damage models are used to analyze the response of the specimen. The damage distribution at two di ff erent time increments both of which are close to the end of the analysis are shown in Figure 2.

Fig. 2: Top row: Evolution of damage band for conventional implicit gradient formulation, Bottom row: Evolution of damage band for LIGD.

The growth of the localization band in case of conventional damage formulation is clearly visible. On the contrary, the localization band stays almost constant for LIGD formulation. Furthermore, although the damage initiates from the