A problem arises when uniaxial tensile tests are conducted on UD composite materials in the fiber direction, that is the failure starts in the clamping area and hence the tensile strength is underestimated. In this study, uniaxial tensile tests in the fiber direction on specimens from unidirectional E-Glass fiber/Vinyl ester matrix composite material are analyzed. The effect of use of end tabs on tensile strength of specimens are investigated and finally the best configuration, including the geometry and the material of end tabs and also the clamping pressure on end tabs, is obtained through numerical simulations. mention the results.