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DNV-OS-C501 Composite Components

Sec.4: Materials - Laminates

I: Properties with damaged or nonlinearly deformed matrix

I300: Experimental approach

Sec.4
I 300   Experimental approach

Fig. 5   Example of axial stress vs. strain curve of a 0/90 laminate to obtain magnitude of the matrix ply modulus of a laminate with matrix cracks.


Sec.4 I
303   The change of G₁₂ is usually due to a combination of non-linear behaviour at low strains and matrix cracking at higher strains. The change may be determined from axial tests on ±45 laminates. The shear modulus of the laminate can be calculated with laminate theory from the ply properties. The initial modulus of the test G₁₂ should be consistent with the calculated modulus based on undamaged ply properties (see B600). The secant modulus at failure of the test G_{12 at failure} should be consistent with the calculated modulus based on an unchanged ply modulus in fibre direction and a modified modulus G₁₂* representing non-linearity and the matrix with cracks. Instead of determining G₁₂* at failure it may be taken at 90% of the failure load. An example of experimental data is given in Figure 6.

Fig. 6   Example of axial stress vs. strain curve of a ±45 laminate to obtain magnitude of the matrix shear modulus of a laminate with matrix cracks.


Sec.4 I
304   Similar procedures may be used on other laminate configurations to obtain ply properties of laminates with matrix cracks or with a non-linear deformed matrix.