The Effect of Crack Orientation on Methanol-Induced Crack Healing in Poly(Methyl Methacrylate)

The line-and the cross-crack healing of Poly(methyl methacrylate, PMMA) under the methanol treatment at 40 degrees C similar to 60 degrees C have been studied. The cross-crack means that the crack plane is vertical to the crack plane of the line-crack. The effective glass transition temperature of PMMAis reduced after the methanol treatment. Both crack healings only occur at the effective glass transition temperature lower than the transport temperature. Both crack closure rates are constant. The closure rate of the cross-crack is higher than that of the line-crack. The analyses of the surfacemorphology and mechanical strength show that there are also two stages for crack healing which is wetting and diffusion. The tensile fracture stress of the healed specimen increases with a rise in volume fraction of the absorbing methanol. The tensile fracture stress of healed PMMA with line-or cross-crack can be recovered to the virgin material. The tensile fracture stress of healedPMMAwith cross-crack is larger than that with the line-crack.