A study of the fracture toughness of acrylic composites using the essential work of fracture method

The Essential Work Fracture approach was used in order to calculate the fracture toughness of acrylic composites. The composite materials were formulated with polymethylmethacrylate (PMMA) as a matrix and either core-shell or multi-layer particles with 10 or 20% volume content. Double-Edge Notched Tension (DDENT) specimens were tested in a universal testing machine at 2 mm/min. It was found that the values of the specific essential work of fracture, we, increased with increase of the particle content. The composites prepared with 10 and 20% core-shell particles reached values of 4.63 and 9.72 kJ/m2, respectively, whereas the composites formulated with 10 and 20% multi-layer particles reached values of 8.36 and 8.42 kJ/m2, respectively. The nonspecific value of fracture for the multi-layer particle composites was found to yield a negative slope, however, from Scanning Electron Microscopy (SEM) micrographs, ductile-to-brittle behavior was observed, i.e., unstable crack growth.