In vitro degradation behavior of carbon fiber-reinforced PLA composites and influence of interfacial adhesion strength

In the present study, carbon fiber-reinforced polylactide (C/PLA) composite s with different interfacial conditions were prepared to determine the infl uence of interfacial adhesion strength (IAS) on in vitro degradation behavi or of the C/PLA composites. Pure PLA and untreated and treated C/PLA compos ite samples were immersed in phosphate buffered saline (PBS; pH 7.4, 37 +/- 0.5 degreesC) for predetermined time periods. These samples were removed a t each degradation time, measured to analyze molecular weight loss, weighed to assess water uptake and mass loss, and mechanically tested to obtain be nding strength, modulus, and IAS. The matrixes in the C/PLA composites show ed higher water uptake and lower mass loss in comparison with the pure PLA. Further, the PLA matrix in the treated composite absorbed less water and l ost less mass and molecular weight than its counterpart in the untreated co mposite. Mechanical tests confirmed that the treated C/PLA composite exhibi ted a slower rate of decrease in bending strength, modulus, and IAS than th e untreated one. The differences in degradation behavior between two compos ites can only be attributed to the difference in interfacial conditions bec ause all other parameters were kept constant. The loss of bending strength and modulus was mainly caused by the interface degradation of the C/PLA com posites. It can be concluded from our in vitro observations that the IAS ha d an obvious influence on the degradation characteristics of the C/PLA comp osites. (C) 2001 John Wiley & Sons, Inc.