Fatigue Behaviour Of Degradable Polylactic Based Natural Fibre Composite

Tey, Yik Yang (2020) Fatigue Behaviour Of Degradable Polylactic Based Natural Fibre Composite. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

Green composites using two or more degradable materials as reinforcement or matrix were promising as non-biodegradable composites substitutes due to their recyclability and sustainability. The aim of this study was to investigate the fatigue behaviour of pineapple leaf fibre (PALF) reinforced polylactic acid (PLA) composite under a cyclic loading. The objective of the study was to compare the effect of fibre loading onto the fatigue life of PALF/PLA composite and to evaluate the damage behaviour of the fatigued PALF/PLA composite. PALF was chemically treated prior to the fabrication process. The PALF/PLA composite was then produced by combination of pre-pre gg ing technique and hot compression moulding. The specimens with fibre loading of 40 wt. % and 70 wt. % were cycled to tension-tension fatigue loading at stress ratio of 0.1 with 4 Hz frequency. The fatigue tests were conducted in load control at 50% and 75% of the ultimate tensile strength of the 40 wt.% and 70 wt.% PALF/PLA composite . For 40 wt.% PALF/ PLA composite , lower stress level (25% UTS) was carried out in order to identify the fatigue limit of the composite . The fatigue life was recorded using S-N diagram, probability of the failure using Weibull analysis while their damage behaviour were evaluated using the secant modulus and energy dissipation analysis. The fatigue test showed as fibre loading increased from 40 wt.% to 70 wt. %, their fatigue life was in cre ased fro m 183 266 cycles to 700 63 I cycles respectively. At low stress level used (25% UTS) no run out was observed, indicated that fatigue endurance of this composite is beyond the 25% UTS. At hi g her stress level, larger dissipated energy was generated for both 40 wt.% and 70 wt.% PALF/PLA composite. The secant modulus of both 40 wt.% and 70 wt.% PALF/PLA composite was increased as the cycle progress due to stiffening effect. The internal damage has occurred after 1000 cycles in both of the composites. Weibull Analysis indicated that the failure behaviour of the composite was depending on the fibre loadings, because a larger damage value (a) is observed at lower fibre loading composite

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