Nondestructive evaluation of interfacial damage properties for plasma-treated biodegradable poly(p-dioxanone) fiber/poly(l-lactide) composites by micromechanical test and surface wettability

Interfacial properties and microfailure degradation mechanisms of the oxygen–plasma treated biodegradable poly(p-dioxanone) (PPDO) fiber/poly(l-lactide) (PLLA) composites were investigated for the orthopedic applications as implant materials using micromechanical technique and nondestructive acoustic emission (AE). PLLA oriented in melt state was brittle and their mechanical strength was not high, whereas PPDO fiber appeared high mechanical strength and flexibility. PPDO fiber reinforced PLLA composite can provide good mechanical performance for long hydrolysis time. The initial interfacial shear strength (IFSS) and microfailure modes of bioabsorbable composites are very important factors because IFSS changes with hydrolytic degradation. The degree of degradation for PPDO fiber and PLLA matrix was measured by thermal analysis and optical observation. IFSS and work of adhesion, Wa between PPDO fiber and PLLA matrix showed the maximum at the plasma treatment time, at 60 s. Work of adhesion was lineally proportional to the IFSS. PPDO fiber showed ductile microfailure modes at the initial state, whereas brittle microfailure modes appeared with elapsing hydrolysis time. With increasing hydrolysis time, the distribution of AE amplitude became narrow and AE energy decreased gradually due to the deteriorated fiber fracture energy. The results of nondestructive AE were reasonably consistent with the trend of microfailure modes by optical fragmentation method.