Fracture Toughness Micromechanics by Energy Methods With a Photocure Fiber-Reinforced Composite

摘要

A fracture toughness analysis for discontinuous fiber reinforcement was evaluated as a function of fiber volume percent (V_f) using advanced flexural bend tests.Fully articulated fixtures with 40-mm spans were used to examine specimens (2 x 2 x 50 mm3) under conditions of Euler-type bending to reduce shearing effects.Testing for fracture toughness in standardized international units (kJ/m2) using fundamental mechanics-of-materials energy methods by strain energy was then applied for assessment of resilience and work of fracture (WOF).Fracture toughness was also measured as strain energy release (SER_(IC)) for the condition of unstable fracture between peak load and 5% maximum deflection past peak load.Energies were calculated by numerical integration using the trapezoidal rule from the area under the load-deflection curve.Fracture depths were normalized using sample dimensions from microscopy imaging for a combined correlation matrix analysis of all mechanical test data.V_f significantly correlated with resilience,WOF,and SER_(IC),but negatively correlated with degree of crack depth with p < 0.0000005.All measured interrelated properties also significantly correlated with one another (p < 0.000001).Significant fracture toughness differences between particulate-filled and fiber-reinforced composites began when adding fiber reinforcement at 10.3 V_f for resilience,5.4 V_f for WOF,and 5.4 V_f for SER_(IC) (p < 0.05).