PSI - Issue 61

Ahmet Çevik et al. / Procedia Structural Integrity 61 (2024) 291–299 Cevik et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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2.3. Experimental Setup and Test Procedure

The experimental setup to apply pure shear loading on fabric curved beams is shown in Figure 4. To apply the shear force to the arm of the curved beam, in-house designed test fixture which is described in Section 2.2 is used. The horizontal arm of the curved specimen is mounted to the loading fixture via bolt, and the load is applied to the specimen by means of freely rotating pin. The vertical arm of the curved specimen is fixed between the support plate and the clamping plate. Support plate can move over the linear rail via rail guideway. This movement prevents horizontal load from occurring on the horizontal arm during the loading process. The experiments are carried out using 10 kN Shimadzu electromechanical testing machine with a test speed of 2 mm/min. Photron SA5 high-speed camera is utilized in all experiments and arranged to center trigger mode where the camera stores the images 1 second before and after the trigger. A 50 mm lens is utilized for the camera positioned 813 mm from the specimen surface. The capture rate is 420,000 frames per second with a resolution of 64×96. The Dedocool Light Kit is used to get sufficient brightness to observe the crack propagation.

Fig. 4. Experimental setup for applying a pure shear loading to a curved beam showing the specimen, clamp, loading fixture and the linear rail.

3. Results and Discussion Three experiments were conducted on fabric curved composite specimens with a stacking sequence of [(45/0) 7 /45/45/0/45]. Load-displacement curves of these experiments obtained from the testing machine are given in Figure 5. The stiffness of specimens Fabric 2c and Fabric 3c is approximately the same, and it is about 27.80 N/mm. The stiffness of Fabric 1, however, is lower than other two specimens, and it is 25.4 N/mm. A sudden load drop is observed in all experiments, corresponding to the initiation of delamination. The specimen Fabric 1c lost 42% of its load-carrying capacity in one load drop, whereas specimens Fabric 2c and 3c lost 69% and 52% of their load carrying capacity, respectively. The stiffness of specimen Fabric 1c after the failure is calculated as 13.31 N/mm. There is not enough data to calculate the stiffness of specimen Fabric 2c and 3c since the experiments of these specimens were stopped just after the failure to avoid a secondary delamination.

Fig. 5. Load-displacement plots for pure shear loading of [(45/0) 7 /45/45/0/45] fabric specimens.