Pim bağlantılı tabakalı kompozit levhalarda ilerlemeli hasar analizi

Fiber reinforced composite plates are widely using automotive, aerospace and space craft industry. For joining composite to composite or composite to metal, mechanical fasteners are used. Pinned connections are a kind of mechanical fasteners and using commonly for joining composites. It is preferred because of low cost, simplicity for application, cheaper than other fasteners and facilitation of disassembly for repair. For application of pinned connections a hole must be opened in the composite plates. Then, the stress concentration locations are appeared on the edge of the hole. The hole is causes stress concentration locations and often causes reduction of load capacity of composite plates. Because of complex failure modes of mechanical joints, designer must be have much more rigorous design knowledge and techniques than traditional methods. In the present sudy, failure behaviour of pinned joint composite materials were analysed experimentally and numerically. The composite materials which were consist of unidirectional carbon fibers and epoxy matrix resin were used with [0o /75o ] 2 symmetric and anti symmetric laminae layups. Numerical analysis was performed with using three dimensionally finite element methods in ANSYS software. In the progressive failure analysis, the Hashin failure criteria and material properties degradation rules were used for predicted failure loads and failure modes. The composite plates produced in IZOREEL firm by supporting FUBAP (Firat University Scientific Research Unit). All laminates were manufactured by press-mould technique. As the matrix material, epoxy CY 225 and hardener HY 225 are mixed in the mass ratio at 100:80. Volume fraction of unidirectional carbon fiber is approximately 70 %. A serial of experiments was performed for determining failure behavior of pin joined and mechanical properties of carbon/epoxy composite plates. The pin loading tensile tests were performed according to ASTM D 953-D standard test method. The failure analysis was performed in ANSYS finite element software with using a computer code which was created with APDL codes. The stress analysis is ended; the stress component of each element is saved in the matrix form. Then each element is tested with failure criteria. If a failure is predicted on any element, material properties are modified by implementing degradation rules. This iteration is continued until catastrophic failure appears. All of the specimens were loaded until catastrophic failure occurred and the general behavior of the composite plates was obtained from the load/displacement curves. The shear-out failure mode was observed for pin displacement value between 0,5-1,5 mm and the bearing failure mode was observed for pin displacement value between 1- 3 mm. Generally, the failure loads affected the geometrical parameters (E/D and W/D). The failure loads were increased with increasing E/D and W/D ratios. However, in this study the failure modes varied with E/D ratios. When E/D ratios were equal 1, the failure mode was observed as shear-out mode. For other values of E/D ratios (i.e. 2, 3, 4, 5), the failure modes were observed as bearing failure. Because of the fiber orientation angle (0o ) of composite plates, failure modes of pinned connections were not impressed the W/D ratios and the net – tension failure was not observed.