PSI - Issue 21

Hande Yavuz / Procedia Structural Integrity 21 (2019) 112–119 H. Yavuz/Structural Integrity Procedia 00 (2019) 000 – 000

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elastic and strength properties have been gathered from CES EduPack software. Among the studied unnotched and notched laminates, first ply failure (HSNMTCRT) was observed in 90° plies for QI and SYMB laminates whereas it was detected in 45° plies in SYM laminate. Failure loads were quantified around 18.5 N/mm, 143.8 N/mm, and 123.6 N/mm for notched QI, SYMB, and SYM laminates, respectively. In the frame of referred damage model, normal force, N xx , does not cause extension-shear deformations, bending-twisting curvatures, and normal stress-shear strain coupling in SYMB laminate. However, in SYM laminate, normal stress-shear strain coupling does exist due the effect of ply orientation which may change initial degradation of stiffness. While keeping the material and layer thickness identical, replacement of -45° lamina with +30° one caused approximately 14% decrease in the matrix tensile failure load. In unnotched laminates, the effect of ply stacking sequence on the matrix failure response was found identical to notched ones. Among the unnotched laminates, the highest matrix failure load was attributed to SYMB laminate (286 N/mm) which accounts roughly to 17% difference compared to SYM laminate. With respect to maximum failure stress, Abaqus (e.g., 773.5 MPa for SYMB) and MATLAB (e.g., 755.1 MPa for SYMB) results were found close to each-other. The computational damage analyses for notched laminates were given in Figure 4. Damage evolves in AS4/3502 material from hole edge to hole boundary in notched laminates more likely due to high stress concentration. Additionally, unlike notched SYMB and SYM laminates, damage evolves in matrix from the outer specimen edges of notched QI laminate. Free edge stresses usually drive the initiation and propagation of failure of such composite laminates.

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Fig. 4. Matrix tensile failure (HSNMTCRT) for notched laminates of (a) QI 90° ply 4, (b) SYMB 90° ply 4, (c) SYM 45° ply 1.