Modeling of creep and creep recovery behaviors of PDLLA/PCL/bioactive glass nanocomposites as promising ACL reconstruction screws: the effects of bioglass reinforcement phase

To study the creep behavior for a series of biodegradable nanocomposites, which are used as implantable devices in the body such as bioscrews, is a crucial factor. In the current paper, we are investigating these biomaterials -short-time creep and creep recover manners- in several classic models.

The creep and creep recovery behaviors of nanocomposites composed of biodegradable polymer blends, poly (D/L) lactic acid (PDLLA) and polycaprolactone (PCL) reinforced with three different contents of 1, 3 and 6 percent weight percentage (Full name?)% bioactive glass nanoparticles (m-BGn) were modeled. Several theoretical models including Findley power law, Burgers and Weibull models were used to establish the relations between m-BGn dispersion and final creep and creep-recovery behaviors of nanocomposites.

The Findley power law model confirmed that the lowest ‘A’ and highest ‘n’ parameters ( A is the amplitude of the transient creep strain and n is the time exponent) belong to the sample with the highest young modulus and the nanocomposites compared to PDLLA/PCL  blends have the lower ‘A’ and higher ‘n’ which can be related to retardation effect of m-BGn on creep strains. Besides, the burgers model results illustrated that all viscoelastic and viscoplastic parameters for nanocomposites possess higher values than those of the neat PDLLA/PCL blend. It means that the addition of glass nanoparticles leads to decrease creep strain , increasing the Burgers model prediction values which have inverse trend with . Moreover, the weibull distribution model results acknowledge that the introduction of m-BGn into PDLLA/PCL polymeric blends cause decrease  in the viscoelastic strain recovery values. This is due to hindering effects of m-BGn on creep recovery behavior of nanocomposites.

The results obtained from modeling of creep-recovery manners of PDLLA/PCL blend and its nanocomposites approved that the bioactive glass reinforcement nanoparticles play  impeding role on creep and creep recovery behaviors..Level of evidence: I.