**3. Determination of lamina properties**

All numerical and experimental studies have been implemented for glass fiber reinforced epoxy based prepreg VPS-7. Initially, the properties of the fibers and resin, which was accepted as isotropic, have been studied experimentally using testing machines Galdabini. The samples of resin and bundles of the fibers were experienced by tensile forces with strains


**Table 1.** Mechanical properties of the composite constituents.


Remark: Index 1 corresponds to the longitudinal ply orientation (along the fibers), whereas index 2 to the transversal ply orientation.

**Table 2.** Mechanical properties of lamina.

The FE mesh has been constructed for the given geometry as swept mesh (see **Figure 3**) consisting of 128,893 domain elements, 37,959 boundary elements and 1350 edge elements. The

All numerical and experimental studies have been implemented for glass fiber reinforced epoxy based prepreg VPS-7. Initially, the properties of the fibers and resin, which was accepted as isotropic, have been studied experimentally using testing machines Galdabini. The samples of resin and bundles of the fibers were experienced by tensile forces with strains

number of degrees of freedom solved for is 625,409.

**Figure 2.** Curvilinear local coordinate systems on the beam surface.

40 Optimum Composite Structures

**3. Determination of lamina properties**

**Figure 3.** FE mesh used at the mechanics problem.

monitored by extensometers. During these experiments, the following elastic moduli have been obtained (see **Table 1**).

The properties of unidirectional lamina, which has transversely isotropic symmetry, were determined both numerically and experimentally for the samples with volume fraction Vf = 0.534. In order to determine the parameters inaccessible through the experimental tests, we used the mixing rule and FE modeling in Abaqus environment according to the recommendation of [20, 21]. The values all found properties are shown in **Table 2**, where bold numbers denote the most reliable values, which have been used in the follow-up investigation. These values have been used for determination of elastic moduli of laminates of chosen structures.
