This work investigated the evolution of the non-uniform distribution of Mode-I strain energy release rate (SERR) along a straight pre-crack front of double cantilever beams (DCB), caused by the anticlastic deformation and the longitudinal free-edge effects. A modified DCB specimen with a curved pre-crack front was introduced in order to alleviate this problem and produce an uniform SERR distribution at the initiation and propagation stages. The first order optimization method was used to determine the appropriate shape of the curved pre-crack front in order to guarantee an uniform SERR during the fracture process. The introduced DCB specimen configuration with the curved pre-crack front was shown to be more convenient for the estimation of a consistent SERR value throughout the fracture procedure without been affected by the visual deviation of the crack length and the non-uniformity ratio of Mode-I SEE distribution along the crack front.