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Slow crack propagation in a heavily‐filled particle reinforced epoxide resin
Author(s) -
Montesg G. M.,
Draughn R. A.,
Simpson T. H.
Publication year - 1987
Publication title -
polymer composites
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.577
H-Index - 82
eISSN - 1548-0569
pISSN - 0272-8397
DOI - 10.1002/pc.750080409
Subject(s) - materials science , composite material , fracture mechanics , viscoelasticity , cracking , crack closure , composite number , particle (ecology) , crack growth resistance curve , oceanography , geology
The fracture properties of two proprietary composite dental restorative materials and a model composite system were studied to determine the effects of filler concentration, exposure to water, and particle/polymer adhesion on subcritical crack propagation. Particle content ranged from 36 to 60 volume percent. The double torsion (DT) test was used to measure relationships between the stress intensity factor ( K 1 ) and the speed of decelerating cracks or the rate of loading in dry and wet materials in air at laboratory conditions. Materials with weak particle/polymer interfaces fractured by continuous crack growth in both dry and wet conditions. In dry and wet materials with strong interfaces, continuous cracking also occurred at the low end of the range of speeds observed (10 −7 to 10 −3 m/s), but under test conditions of high crack speeds unstable (stick‐slip) crack propagation was found in dry specimens and in wet model composites with 41 percent vol, filler. Water had a corrosive effect lowering K 1 c for continuous crack propagation. The exponential dependence of K 1 c on crack velocity, representing the viscoelastic response of the materials, was positively correlated to the filler concentration and the plasticizing effect of water. Observations on fracture surfaces indicate that low velocity cracks (<10 −5 m/s) propagate through regions of high stress concentrations (interfaces, corners, pores) while at higher crack velocities failure occurs by a combination of interparticle and transparticle fracture.