Investigation Of The Stress Intensity Factors Of A Reinforced Polymeric Composite At Different Fracture Modes

Year 2021, Volume: 5 Issue: 1, 7 - 14, 31.03.2021

Dıckson Davıd Olodu , Cyril Aliyegbenoma

Abstract

Reinforced polyester composites potentials cannot be fully harnessed and exploited unless their fracture modes and failure mechanisms under impact force are fully understood, and appropriate design tools for failure prediction are developed and validated. This study therefore, investigate the stress intensity factors of a reinforced polymeric composite (reinforced polyester composite) at different fracture modes. In this study, the polyesters were reinforced with E-glass fibre in forms of woven roving with either hard or soft mat. Fourteen (14) test samples with dimension 210mm by 150mm were developed, cut and tested in accordance with America Standard of Testing Machine (ASTM) for polymeric composites under Mode I, Mode II and Charpy impact test conditions respectively. Destructive test method was used as the process was observed and studied under a video motion camera, making it possible to monitor the damage as it progressed; crack propagation and final fracture of the specimen on a macroscopic scale level were taken. From the experiment, it could be established that the stress intensity factor is a function of the presence of a crack on the composite structure, the magnitude of the load, and the thickness of the specimens. These factors influence the rate of crack propagation in the test specimens. Specimen I was found to have the smallest stress intensity factor with a thickness of 10.3mm at maximum load of 0.91kN. This could be traced to the form and volume fraction of reinforcement. Furthermore, specimen C was observed to possess the highest optimal stress intensity factor of 9.49 MPa.m1/2 and 2.49 MPa.m1/2 at critical stress of 25.82MPa and 7.12MPa for mode-I and mode-II respectively. Therefore, specimen C had the highest tendency for crack to propagate due to excessive build-up of stress around the crack tip at every stage, as this could be traced to the composition of reinforcement.

Keywords

Fracture Modes,, Reinforced Polyester Composite,, Specimens,, Stress Intensity Factors.

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