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This paper presents the effect of fiber orientation angle on the stress intensity factor SIF for carbon epoxy composite plates with single-edge, center, and inclined cracks of varying lengths under tensile load. The stress intensity factor and shape factor were calculated individually for each case, with nine different fiber orientation angles computed using the extended finite element method XFEM concepts. It is found the stress intensity factor increases with increasing crack lengths while the shape factor decreases. In the case of single edge cracks, the SIF increases in the average value reached (173 %) for composite plates with different fiber orientation angles, while in the case of the center crack, the average value of SIF reaches (81 %). It was observed in this study that the increases in stress intensity factor and the decreases in the shape factor with different crack lengths were more stable in the composite plate with a fiber orientation angle of 75°. The higher values of SIF at an angle of 75° are because of the high probability of fiber slippage at 75° due to induced shear stresses in addition to the tensile stresses at the fiber-matrix interface. As a result, the crack tip has a high-stress intensity factor.

n this study, loading was carried out for several types of perforated plates, such as circular, rhombic and rectangular holes, where the holes were arranged in two types, namely straight arrangement and alternating arrangement. The stress intensity factor and shape factor were calculated for each case, taking into account the diameter of the holes. So, it is found the SIF increases significantly when the plate is perforated, and the same applies to the shape factor, also increases. In the case of circular holes, the increases in the average value of (SIF) reached to (80.88 %) when the plate was perforated with alternated arranged of circular holes, while the straight arrangement of circular holes the increases of average values of SIF reach to (67.55 %). Either in the case of rhombus holes: the SIF values are increases to (51.07 %) when the plate was perforated with the alternated arrangement, while in the straight arrangement of holes the (SIF) increase to (35.43 %). It was observed through this study, the increases of stress intensity factor and the shape factor with different crack lengths were more stable in the plate that perforated with an alternated arrangement of holes than the straight arrangement. The higher values of stress intensity factor obtained when the plates were perforated with circular holes, due to the circular shape has more stiffness, so the Absorption of force will be small Compared with the rhombus and rectangular shape that will be less stiffness which the absorption of strength is greater.

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Corrugated plates play very important role in variousengineering applications. The occurrence of crack in the body ofcorrugated plate might results in catastrophic failure. In thepresent paper there are different profiles of corrugated plates(trapezoidal, sinusoidal and triangle) that are studied. In eachprofile the stress intensity factor and shape factor werecalculated for various crack orientations, various corrugationangles and different curvature radius for the same profile. Theyare all subjected to different loading conditions using ExtendedFinite Element Method (XFEM).It is found the stress intensity factor when load applied parallelto corrugation direction is higher when load appliedperpendicular to corrugation direction. Also found that thestress intensity factor increase by 115% when curvature radiusincreases with the load applied perpendicular to corrugation.This study also found and explained that the stress intensityfactor increases slightly when the corrugation angle of the trianglecorrugated plate increases. In all cases studied, the trapezoidalthe corrugated plate shows the lower values of the stress intensity factorcompared to the sinusoidal and triangle corrugated plates.