PSI - Issue 28

Anurag Singh et al. / Procedia Structural Integrity 28 (2020) 2218–2227 Anurag Singh/ Structural Integrity Procedia 00 (2019) 00 – 00

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Figure 7: % inc/dec of various mechanical properties with first and last stage of degradatopn of PGLA fibres

For the last stage of degradation of the PGLA fibres; their capability to withstand mechanical loading is lost; they are more brittle compared to the previous stages of degradation. Figure 8 shows the pigmentation and thinning of the PGLA fibres. Brittleness increase as the chain scission of the polymer has resulted in a reduction of the plastic flowability, which results in changing of ductile behaviour to the brittle behaviour. Figure 7 shows the % increase or % decrease in mechanical properties for the first stage of degradation (5 days) and the last stage of degradation (30 days). For 5 days, all the mechanical parameters showed an increase compared to dry PGLA fibres. Initial stiffness showed similar values except at the highest strain rate. For force at yield point, the value of the force at the lowest and highest strain rate showed lower values than the dry PGLA fibres. Effect of saturation explains this increase in the values of mechanical parameters. PGLA fibre here is a multifilament, on getting saturated fibres experiences less friction among them and because of which they are experiencing higher mechanical properties. Hence, PBS acts as a lubricant between the fibres. For the last stage of degradation, chain scission results in lowering of all the mechanical parameters except the force at the yield point. Chain scission was significant after the 15 days of degradation, which led to the reduction in the strength of PGLA fibres for further stages of degradation. Figure 9 shows the force at yield and force at the break with degradation days and strain rate. Force at yield increases with the strain rate and with the increase of degradation force at yield increases up to 15 days of degradation, and then it shows a decrease. Force at the break for the PGLA fibres showed an increase with strain rate, but it is not as prominent as the force at yield. Force at break follows the same pattern of increase up to 15 days of degradation after which chain scission leads to decay in the mechanical properties.