International Journal of Fracture 34:57q54 (1987) © Martinus Nijhoff Publishers, Dordrecht Printed in the Netherlands 57 Determination of SIF in a cracked plane orthotropic strip by the Wiener-Hopf technique H.G. GEORGIADIS 1 and G.A. PAPADOPOULOS 2 t33-35 G. Papandreou Str., 16231 Athens, Greece; 2Division of Mechanics, Department of Engineering Sciences, The National Technical University of Athens, 15773 Athens, Greece Received 21 October 1986; accepted 26 December 1986 Abstract. The stress intensity factor for a long cracked strip was determined within the context of the linear orthotropic elasticity. The body had the form of an infinite strip containing a semi-infinite crack at the middle distance of the strip faces. Fourier transforms in combination with the Wiener-Hopf technique were employed to evaluate asymptotically the cleavage stress and its intensity at the crack tip. 1. Introduction In the realm of linear elastic fracture mechanics (LEFM), the main interest is in the elastic stress intensity factor at the tip of cracks or sharp notches. As is well-known the determination of this factor is indispensable for the application of the Griffith-Irwin fracture concepts [1, 2]. In the early years of development of LEFM, researchers confined themselves to finding solutions for crack problems in bodies of infinite dimensions. In recent years, however, there is an increasing interest in analytical solutions in cracked finite bodies. In addition, more general constitutive relations are considered for the mechanical response of the cracked solids involving anisotropy, inhomogeneity and non-linearity. As a consequence, the math- ematical crack problems become more and more difficult and the techniques for their solution more and more sophisticated. In this paper we have considered a cracked long strip made by an orthotropic elastic material involving four independent elastic constants. The strip contains a semi-infinite crack parallel to and equally spaced from the strip faces. The corresponding isotropic case of the foregoing problem was treated by Knauss [3] (see also discussion and correction by Rice [19]) whereas Nilsson [4] considered the isotropic steady-state elastodynamic case. Recently, Sih and Chen in a treatise on cracked composite bodies [5] considered many crack problems of a similar fashion, but the present case was not included. Infinite orthotropic strips with internal cracks were also considered by Konishi and Atsumi [6] and Satapathy and Parhi [7]. It is also worthwhile to mention some other analytical works concerning the double cantilever beam configuration (which involves a cracked strip loaded by concentrated forces near the crack faces) carried out by Kanninen [8, 9] and Fichter [10]. 2. Basic preliminaries The material we considered was orthotropic with two mutually orthogonal axes of elastic symmetry in the plane. With respect to the principal material-axes of an orthotropic plate,