Composites are currently used in various industries and these materials are widely used in traortation and building industries. In the meantime, random fiber composites have been used extensively as well as other types of composites. Performing engineering analyzes on composites reduces the process of try and errors in production and use. Discontinuous fiber composites are among the composites that can be difficulty analyzed due to the completely random orientation of fibers in their structure. One of the most important problems that has not been addressed so far is the unit cell analysis with real yarn dimensions. Therefore, in this research, the modeling and analysis of the unit cells of the discontinuous fiber composite in Abaqus finite element software is done with real dimension of yarn and the effects of shortening the length of the yarns on the elastic properties of these composites are evaluated. Also, since in the actual samples of these composites, the fibers are curved by modeling two unit cells of straight yarns and other curved yarns, the effect of yarn curvature on mechanical properties is also studied. In each of these modeling, the yarns are distributed to the ratio of the desired volume fraction, completely randomly and without interfering with each other within each unit cell. The unit cells should be made in such a way that the desired composite to be achieved by putting multiple unit cells together. During each of these analyzes, the dimensions of the appropriate unit cell are also checked for each length of yarn. As well as extracting the elastic properties of each unit cell from the Abaqus finite element software, these properties are obtained by micro-mechanical methods provided for the discontinuous fiber composites. Also, in order to obtain experimental results and verify the results obtained from theoretical analysis, samples of this composite are made. For this purpose, the desired nonwoven is made of glass fiber and it is made by injection of polyester resin to these composite sheets in two ways: Hand lay up and VIP. After extracting samples from each composite and performing tensile tests on them, these two methods of composite construction are compared and the advantages and disadvantages of each are expressed. Comparing the results of finite element analysis, micromechanical relations and experiments showed a good correlation between the results. Keywords Discontinuous fiber composites, Fiber random distribution, Finite element analysis, VIP method, Injection method in vacuum, Hand lay up method, Micromechanical analysis
