PSI - Issue 28

Anurag Singh et al. / Procedia Structural Integrity 28 (2020) 2218–2227 Anurag Singh/ Structural Integrity Procedia 00 (2019) 000–000

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the mechanical characterisation results, now they have better mechanical characteristics when compared with the dry PGLA fibres or undegraded PGLA fibres. Also, on the application of load, friction is generated between the dry filaments. On soaking PGLA fibres in the PBS for degradation, these PGLA fibres absorb the water molecule and become soft. Water acts as the lubricant between the filaments. Thus, fibres can reach higher load after saturation with PBS. Presence of PLA in the blend helps PGLA have significantly lower degradation, and the mechanical properties increase up to 15 days of degradation time. After 15 days, mechanical properties start to decay. Finally, for 40 days of degradation, PGLA fibres completely lose the mechanical properties; at 40 days fibres became fragile and showed pigmentation. PGLA is a semi-crystalline polymer; percentage crystallinity varies from 30-40% with different degradation stages. It is a two-phase system, crystalline and an amorphous phase coexist, crystalline phase and the amorphous phase are not entirely homogeneous. This work helps in understanding the long-term behaviour of this PGLA blend (90:10) which is assumed to mimic the collagen fibres as the basic building block of ACL. Further, design and simulation of the ACL augmentation device in the form of the scaffold make use of these mechanical parameters of PGLA fibres for further development as a composite cord with different biodegradable filaments.

Figure 9: Force at break and force at yield at different strain rates with increase of degradation time