Maximum tangential stress coupled with probabilistic aspect of fracture toughness of hybrid bio-composite

The statistical aspect of mode I, mode II and mixed mode I/II fracture toughness of epoxy based bio-composite reinforced with 20 wt% walnut shell particle and 10 wt% coconut fiber is studied. The bio-composite is fabricated by the squeeze casting method. A series of fracture tests are conducted on hybrid bio-composite using three point bend, four point bend and semicircular arc bend specimen. The statistical distribution of normalized geometry parameters, T stress, crack tip plastic zone size, particle and fiber size are studied. Generalized maximum tangential stress criterion is modified considering the stochastic nature of the geometry and strength parameters assuming them to follow two parameters Weibull probability distribution. The model developed is applied to the bio-composite and predicted results are compared with the experimental values. Very good agreement is found between the experimental results and predicted results. The variability in the fracture toughness values are correlated with the particle and fiber size determined from scanning electron microscopy.