Issue 53

A. Desai et alii, Frattura ed Integrità Strutturale, 53 (2020) 426-433; DOI: 10.3221/IGF-ESIS.53.33 429 Here ‘ F ’ is the peak load, ‘t’ is the thickness of the specimen and F I (a/W) and F II (a/W ) are the non-dimensional geometrical factors for both pure Mode-I and pure Mode-II. Fracture tests were performed with a universal tensile testing machine under a loading speed of 2 mm per minute. Tests were conducted three times for each specimen laminates. The critical stress intensity factor ( K IC & K IIC ) value was calculated from this peak load by equations that have been established on specimens of the type described in He and Hutchinson [3]. Figure 2: Specimen configuration used in the analyses W=18mm, d= 26mm, L=52mm, a=9mm. Figure 3: Arrangement of FPB specimen loaded at UTM R ESULTS AND DISCUSSIONS Fracture behavior of glass-epoxy polymer composite he specimen is loaded for 6 different crack positions (i.e. d/W =1.5 constant for all the specimens). These 6 cases correspond to the different crack distances from the middle of the specimen by varying the s/d ratios from 0 to 1 by an increment of 0.2. Fracture behavior of laminates for different loading positions in the specimen, showed that the crack in the specimen initiated at the crack tip and then propagated along the fibre/matrix interface. Thus, for loading positions other than s/d =0 and s/d =1, the cracks propagate under Mixed mode loading conditions. A set of five specimens were prepared for each loading conditions and the peak load experienced by the specimen is computed by the average of best three specimen results. It is observed that the deviation in the load is less than 2.5%. The estimated average load vs . displacement values is plotted in Fig. 4 for (0/45)° and (0/90)° fiber oriented glass/epoxy. Load is applied for various s/d ratios of the specimen to calculate the stress intensity factor ( K ). Load displacement curves from the experimental fracture are gathered and from these curves, the peak loads (F) at fracture are used to compute critical Mode-I and Mode-II stress intensity factors. Tab. 1 and Tab. 2 gives peak load values and corresponding stress intensity T Compression plate FPB specimen Fixture