抄録
Effect of notch tip radius on fracture behavior of compact tension type specimens of sheet-molding-compound (SMC) composites was studied. Notch tip radii (ρ) were from 0.09mm to 2.1mm. Acoustic emission (AE) measurements and microscopic observations were carried out to examine damage formation procedure around the notch tip. Optical observations by a dye-penetration method exhibited that fracture patterns in the specimens of ρ≤0.56mm were quite different from those in case of ρ=2.1mm. For ρ≤0.56mm, a main-crack initiated at the notch tip and grew in parallel with generation of many sub-cracks surrounding the main-crack tip. For ρ=2.1mm, on the contrary, during main-crack growth, sub-cracks propagated in radial directions. With increasing notch tip radius, there were observed little increase in the maximum load, AE cumulative event counts and standard deviation of AE source locations. Strain energy at the maximum load slightly increased with increasing notch tip radius in a range 0.09mm≤ρ≤0.56mm. States of fiber strands at the notch tip affected parameters on strength more significantly than notch tip radii within ρ=2.1mm.
