Interfacial Effects on Impact Fracture of Advanced Polymers

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8.1 Dependence of fracture toughness of rubber toughened polymers on impactvelocityUsing a high-speed tensile tester developed at Lausanne Institute of Technology, rubber toughened PMMA tensile specimens were tested for their fracture toughness dependence on the tensile rate up to 10 m/s. Specimens containing 20 wt% rubber particles exhibited decrease of the toughness at an elongation speed of 1 m/s.whereas specimens of 40 wt% showed a slight decrease in the toughness at 10 m/s. By TEM observation, it has been found that main causes for the toughening are cavitation of rubber particles accompanied by craze initiation, craze growth, craze branching and shear deformation at extensively deformed region. Craze branching behavior has been found for the first time by this work.8.2 Miscibility of heat-resistant, high toughness polymer blendsFlory-Huggins free energy theory was applied to a study of miscibility of three element polymer blends (grafted SAN,free SAN and SMI) to design most appropriate material regarding the AN weight contents in gSAN and fSAN,and PMI in SMI for the improvement of impact toughness. The analysis yielded that the optimum weight percents are gSAN (33), fSAN (30) and SMI (55).8.3 Impact performance of FRP with thermoplastic matrices and damage mechanismat interfaceGF/PA6, CF/PA6, GF/mPA6 and CF/mPA6 (m ; modified) were tested under tensile loading at various loading rate up to 10 m/s. It has been found that GF/PA6 is the toughest among the four FRPs.8.4 Reliability study of impact testersBy introducing an extensometry technique developed at Lausanne Institute of Technology, one-element, and two-element high-velocity extensometers were constructed for experimental verification of dynamic effects in impact testing.