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Question 1 Damage in composites 1.1 A unidirectional E-glass/epoxy composite plate having a central through thickness crack of length 3a is subjected to a uniaxial stress o, as shown in the figure below. The unidirectional fibres are oriented at an angle a with respect to the direction of the crack, where a is in radians. The model fracture toughness of the composite Kica, varies with the angle a according to the empirical equation. KKIIIIII = [0.739aa2 +0.19aQ + 1]KKIITIO, where KKIT110 = 1.47 MPa m1/2 is the fracture toughness at the angle aa = 0 (i.e. when the crack is parallel to the fibre direction). The applied stress is ag = 150 MPa. Crack Elliptical zone assumed to be relaxed due to presence of crack Figure1: Griffith crack: A through-thickness crack in a uniaxially stressed plate of infinite width (Gibson 2016) Determine the critical size x for the cases, where the crack is (i) perpendicular to the fibres and (ii) parallel to the fibres (10) moohanime in the following Dircus facial clic