Calibration and evaluation of performance of the models using a test case

Li performed tests (Li, X. et al, 2000) on a sandwich member of length 210mm completely restrained at its top face and loaded uniformly across its width at one end of the bottom facing. The specimen carried a pre-implanted delamination of 51mm. The geometry, the loading and the boundary conditions of the test specimen are indicated in Fig. 2. Of the three groups of specimens tested, only one group identified as “KKV sandwich”, exhibited no crack kinking into the core. After the first micro-kink, the crack propagated in the core parallel to the interface about 0.5mm below the face/core interface. The specimens were loaded at varying, but small angles to the normal of the top face and the one loaded normal to face is selected for investigation here.

The facing sheets are made up of E-glass/vinyl ester while the core material is H200 Divinycell PVC foam. Table 1 lists the elastic properties of the materials. Here we use the averaged elastic properties as determined from compression and tension tests. (The most important property is the effective modulus in the longitudinal direction which determines the slope of the initial linear phase prior to crack initiation which varied from 23.2GPa in compression to 26.0GPa in tension – an average value of 24.6GPa is used for the comparison with experiment.).

Table 1: Material properties of Li’s specimen

Material Property

Li’s specimen

Face sheet

Core

Longitudinal Young’s modulus, Ex (GPa)

24.6

0.165

Transverse Young’s modulus, Ey (GPa)

11.8

0.263

Out-of-plane Young’s modulus, Ez (GPa)

13.5

0.165

Poisson’s ratio, Uxy

0.31

0.32

Poisson’s ratio, Uxz

0.533

0.32

Poisson’s ratio, Uyz

0.446

0.32

In-plane shear modulus, Gxy (GPa)

3.78

0.0644

In-plane shear modulus, Gxz (GPa)

9.19

0.0644

In-plane shear modulus, Gyz (GPa)

Critical strain energy release rate for mode I, GIc (J/m2)

3.74

1270

0.0644