**4. Numerical analysis**

In the numerical study, the entire specimen was modeled using solid layered 46 element in ANSYS 12.1. Specimens with 25 mm width have 25000 mesh elements

**Figure 16.** *Detailed view of FEM model of DCB test specimen used under loading.*

**Figure 17.** *Forces and boundary conditions of FEM: a) nodal forces, b) boundary conditions.*

and specimens with 40 mm width have 40000 mesh elements. A linear elastic finite-element analysis was performed under a plane strain condition. The loads corresponding to the crack initiation in the DCB tests were used to the finite element solution (see in **Figure 16**).

As a part of study, the variation of versus different width length has been investigated. The load was applied as a nodal force at the upper and bottom layer of the composite as shown in **Figure 17(a)** and all nodes along the right side of the composite were restrained in y direction as shown in **Figure 17(b)**. The mechanical properties, which were obtained experimentally, of woven-fabric-reinforced glass/ epoxy composite materials are given in **Table 1** and were used during the analysis. The numerical analysis results of the fracture toughness that was obtained by FEM are given in **Table 3**. It is seen that, the obtained numerical values are good comparability with the corresponding experimental results for all experiment groups. As a result of numerical analyses, it can be seen that the fracture toughness increases slightly relative to the amount of decreasing width as mentioned in ASTM D 5528–01 standards, it means that the change of width of DCB specimen is not a great effective parameter for interlaminar fracture toughness values.

The results of experiment tests and numerical analysis showed good agreement demonstrating the effectiveness of the proposed experiment and numerical methods.


#### **Table 3.**

*Interlaminar fracture toughness of the woven and woven 45 with different width.*

*DOI: http://dx.doi.org/10.5772/intechopen.99268 Failure Modes in Fiber Reinforced Composites and Fracture Toughness Testing of FRP*
