Trans RINA, Vol 152, Part B2, Intl J Small Craft Tech, 2010 Jul-Dec
Figure 5.3: Acoustic Emission parameter Correlation for Layup 3 specimens 5. FINITE ELEMENT ANALYSIS RESULTS
The comparative study to validate the FEA results with the experimental results is presented in this section. Non- linear static analysis was conducted on L-Bend curved composite
specimens subjected to bending load.
Interlaminar tensile and shear stresses were calculated just before the first failure. The interlaminar tensile stress was maximum at the lower end of the radius of the bend and this location was predicted as the probable location of initial failure as shown in Figures. 6.1 and 6.3. Through thickness interlaminar tensile and shear stress distribution is shown in Figures 6.2 and 6.4. Interlaminar matrix crack occurred due to excessive interlaminar stress and delamination initiated at the lower end of the bend for all three layups. The critical interlaminar tensile and shear stresses of all the three layups are presented in Figures 6.1 & 6.3. The theoretical interlaminar tensile stress on the extreme surfaces is zero. But due to positioning of the Gauss points which do not sit on the surface of the elements, interlaminar stresses calculated at this point is a non-zero value.
In layup 1, the material was same throughout the laminate. Figures 6.1a and 6.3a shows the ILTS and ILSS stress distribution in the bend at increment number 65
interlaminar tensile stress curve was linear until the mid- thickness and drops to near zero on the surface as shown in Figure 6.1. In the first layup, the initial failure
occurred at a displacement of 64.08mm purely due to interlaminar tensile stress at 9.65 MPa, between second and third layer, mid-width and at an angle of 18.260. Further loading caused the laminate to straighten up, creating interlaminar tensile stress in the inner surface and interlaminar compressive stress on the outer surface.
The second layup consisted of four layers CSM and three layers DB. The first failure occurred between the second (DB) and third (CSM) layer. Figures
6.1b and 6.3b
shows the ILTS and ILSS stress distribution in the bend at increment number 75 for layup 2. Delamination occurred at an angle 21.890 due to peak interlaminar tensile stress of 10.03 MPa. Delamination progressed until all the layers failed and the structure collapsed. Addition of DB layers slightly increased the load carrying capacity as well as the first failure deflection up to 66.80mm compared to all CSM of 64.08mm. The shear stress distributions for all the three layups are shown in Figures 6.3 & 6.4.
for layup 1 just before the first failure. The
With the third layup, first crack occurred between third and fourth layers, UD and DB respectively. Figures 6.1c and 6.3c shows the ILTS and ILSS stress distribution in the bend at increment number 48 for layup 3 just before the initial failure. Addition of unidirectional fibres increased the stiffness and the first crack occurred at 79.40mm. The maximum interlaminar tensile stress was at an angle of 14.600 and maximum shear stress of 10.22MPa at the lower end of the laminate curvature.
B-102
©2010: The Royal Institution of Naval Architects
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66