Failure Of Epoxy Research Articles

The new indicator coating to detect the place of barely visible impacts on aircraft composite structures

There was developed indicator coating made of epoxy resin filled with hollow glass spheres of the volume fraction up to 50% on GFRP substrates. This coating has a high sensitivity to local impacts changing light reflection by the failure of epoxy and glass spheres in the contact area. Mechanical behaviours of the coating are close to the pure epoxy resin but the density is twice less. We also provided experimental data concerning the contact traces under barely visible impact and the numerical model to predict residual traces onto indicator coating with GFRP substrate.

Preparation and Properties of Epoxy‐Clay Nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of adding different contents of nanoclays on the physical, mechanical, and thermal properties of the epoxy resin system used in composite pipes manufacturing. Diglycidyl ether of bisphenol‐A (epoxy) with a cycloaliphatic amine heat curing hardner was reinforced by 1–7 wt.% of an organically modified type of montmorillonite. SEM results showed the change in failure of epoxy from brittle to tough mode by addition of nanoclays. X‐ray results indicated some degree of exfoliation by 1 wt.% clay and a decrease in d‐spacing in higher clay loadings after that. The heat‐distortion temperature of epoxy-clay nanocomposites increased from 125.5 to 138.7°C with 3 wt.% organoclay loading. Tensile and flexural modulus increased with increasing clay loading in this type of nanocomposite, but addition of organically modified clay decreased the tensile and flexural strengths and tensile elongation at break. Addition of 7 wt.% nanoclay improved the impact strength by 25.6%.

Failure of Epoxy and Hydroxy Fatty Acids to Cause Egg Discoloration When Fed to Laying Hens

THE cyclopropenoid ring containing fatty acids, sterculic and malvalic, have been shown to give positive Halphen reactions (Macfarlane et al., 1957; Faure, 1956) and to cause pink-white discoloration in stored eggs from hens fed these compounds (Shenstone and Vickery, 1959; Masson et al., 1957). Evans et al. (1962) isolated from 4,000 grams of crude cottonseed oil, a 45 gram fraction of fatty acids which gave a strong Halphen reaction and caused pink-white discolorations in stored eggs from hens fed it. Treatment with urea separated the concentrate into two fractions, a urea insoluble one that gave a strong Halphen color reaction and variable degrees of pink-white discoloration and a urea soluble fraction which gave a negative Halphen reaction but gave consistent pink-white discoloration. More than 90% of the methyl esters of the urea soluble fatty acids had gas-liquid chromatographic retention times similar to methyl linoleate. No methyl esters were detected in…