Toughening of denture base resin with short deformable fibers

Fracture resistance of polymer reinforced with short fibers consists of a sum of contributions from matrix and fiber fracture, fiber debonding and pull-out. The existing models for predicting dependence of fracture toughness on structural variables were derived for the commercially important fiber volume fractions, i.e., for vf ⩾ 0.1. In this contribution, modification of the existing model for the dependence of the critical strain energy release rate, GIC, on the fiber type, length and aspect ratio, interfacial adhesion and volume fraction has been attempted to allow predictions at low vf < 0.10. The predictions based on the modified model were compared with experimental data on fracture toughness of lightly x-linked PMMA used to manufacture base of removable dentures toughened with short randomly oriented deformable fibers. The composite toughness was measured under impact loading to simulate typical mode of fracture of removable dentures. The GIC for composites containing short Kevlar 29, S2-glass and poly(vinyl alcohol) (PVOH) fibers were obtained using instrumented Charpy impact tests at room temperature and impact speed of 1.0 m/s. Theoretical prediction based on the proposed model and experimental results agreed reasonably well.