The Effect of Micron-Rubber and Nano-Silica Particles on the Fatigue Crack Growth Behavior of an Epoxy Polymer

Abstract

A thermosetting epoxy polymer was hybrid-modified by incorporating 9 wt. % of CTBN rubber micro particles and 10 wt. % of silica nano-particles. The unmodified and the hybrid-modified resins were poured into steel moulds and cured to produce bulk epoxy polymer sheets from which standard compact tension test specimens were machined. Fatigue crack growth tests were conducted using a 50 kN servo-hydraulic test machine, with following test parameters: stress ratio, R = σ min /σ max = 0.1, sinusoidal waveform and frequency, ν = 3 Hz. The crack length was monitored by compliance technique. The fracture surfaces were observed in a high resolution scanning electron microscope. The fatigue crack growth rate of the hybrid epoxy polymer was observed to be significantly lower than that of the unmodified epoxy polymer. The threshold stress intensity factor range, ∆K th , of the epoxy polymer was observed to increase by the addition of micron-rubber and nano-silica particles. The energy dissipating mechanisms viz., (i) cavitation of the rubber microparticles followed by plasticdeformation and void growth of the epoxy and, (ii) silica nanoparticle debonding followed by plasticdeformation and void growth of the epoxy, were observed to be operative and contribute for the reduced crack growth rate in the hybrid epoxy polymer.

Enhanced fatigue behavior of a glass fiber reinforced hybrid particles modified epoxy nanocomposite under WISPERX spectrum load sequence

“…In an earlier investigation [42] we have observed that the fatigue crack growth rate of the hybrid bulk epoxy (containing both micron-rubber and nano-silica particles) is over an order of magnitude lower than that of the neat epoxy. Further, we have observed that the use of such a hybrid matrix in GFRP enhances the constant amplitude fatigue life due to suppressed matrix cracking, delayed initiation of delamination and reduced crack / delamination growth rate [24].…”

“…5 clearly indicate the underlying mechanisms, i.e. suppressed matrix cracking, delayed initiation of 11 delamination, and reduced crack / delamination growth rate [42], for improved spectrum fatigue behavior in the GFRP-hybrid composite.…”

“…5 clearly indicate the underlying mechanisms, i.e. suppressed matrix cracking, delayed initiation of 11 delamination, and reduced crack / delamination growth rate [42], for improved spectrum fatigue behavior in the GFRP-hybrid composite.It may be noted that the fatigue life enhancement is about eight to ten times under constant amplitude loads [24] whereas, it is reduced to about four to five times under WISPERX load sequence as observed in the present investigation. Load interaction effects in composites could alter the fatigue lives of composites significantly.…”

The Fatigue and Fracture Behavior of Micron-Rubber and Nano-Silica Particles Modified Epoxy Polymer

“…6. In an earlier investigation, 31 it has clearly been shown that the fatigue crack growth rate of the hybrid-modi¯ed epoxy polymer is signi¯cantly lower than that of the neat epoxy polymer.…”

Hierarchically rough, mechanically durable and superhydrophobic epoxy coatings through rapid evaporation spray method

“…Small rough features are required to enhance hydrophobic character of the coating but these nano-scale structures are protected (Fig. 1) by a large, strong topography of epoxy and the combination of amine and silica nanoparticles enhances the stress resistance of the bulk material [26]. With high impact strength hydrophobic coatings usually deteriorate due to the brittle materials used, but epoxy is slightly elastic and can endure high forces before cracking or shattering which increases the overall durability and lifetime of the epoxy coating.…”