The purpose of the present study is to investigate the quasi-static and the viscoelastic behavior of epoxy resin reinforced with starch powder. An increase in the elastic modulus on the order of 42% was achieved; a behavior that was predicted by the modulus prediction model (MPM). Next, the composite was subjected to flexural relaxation experiments, in order to determine the relaxation modulus, at different filler-weight fractions and flexural deflections imposed. The viscoelastic models of the standard linear solid, the power law model and the residual property model (RPM) were applied in order to simulate/predict the stress relaxation curves. Predicted values derived from the application of the above models were compared to each-other as well as to respective experimental findings. From the above comparison it was proved the superiority of the RPM model in predicting both the linear and the nonlinear viscoelastic response of the materials investigated.

Epoxy resin composites with different weight fractions of TiO 2 microparticles (1%, 5%, 10%, 15%, 20%) and of TiO 2 nanoparticles (0.5%, 1%, 2%, 3%) were prepared. The particle size of the nanoparticles was averaged around 21 nm while the particle size of the micro TiO 2 particles was averaged around 0.2 µm. The morphology of the manufactured particulate composites was studied by means of scanning electron microscopy (SEM). The mechanical properties of both nanocomposites (21 nm) and microcomposites (0.2 µm) were investigated and compared through flexural testing. Furthermore, the effect of displacement-rate on the viscoelastic behavior of composite materials was investigated. The flexural tests were carried out at different filler weight fractions and different displacement-rates (0.5, 5, 10, 50 mm/min). The influence of TiO 2 micro-and nanoparticles on the mechanical response of the manufactured composites was studied. For micro TiO 2 composites, a maximum increase in flexural modulus on the order of 23% was achieved, while, in the nanocomposites, plastification of the epoxy matrix due to the presence of TiO 2 nanoparticles was observed. Both behaviors were predicted by the Property Prediction Model (PPM), and a fair agreement between experimental results and theoretical predictions was observed.Polymers 2020, 12, 22 2 of 13 in improving the mechanical properties of the composite. The lower the filler diameter, the higher the filler surface/contact area is. Thus, in case of micron sized particles, the size of the low-density interfacial region of the pure polymer surrounding the inclusion is higher, so that the contribution of the filler is reduced, concluding that the mechanical properties of the composite will not be improved that much [6]. On the contrary, the nanoparticles can fill up the weak regions within the epoxy resin, and thus increasing the filler-matrix interaction force. The increase of the extent interfacial region can significantly improve the mechanical properties of the epoxy/nanocomposite. However, the nanoparticles have a difficulty to disperse into the matrix, so it is crucial to find the proper manufacturing technique to improve particle dispersion within the matrix material. A technique that is commonly applied is the ultrasonic homogenization; however, as every technique has its disadvantages. More precisely, this technique decreases the gelling time of the epoxy resin [7][8][9][10][11].The mechanical response of particulate reinforced composites also depends on the rate of deformation. It was found that particulates increase the strain rate sensitivity concerning tensile modulus, but this sensitivity decreases when measuring yield strength [12]. The effect of strain rate on the flexural properties of some polymer matrix composites has been studied and, as it was found, the flexural modulus and flexural strength both increase linearly with the logarithm of the strain rate [13]. Furthermore, the strain-rate sensitivity seems to be slightly more pronounced in shear than in tension and comp...

The present investigation aims to take a step forward for the transfer of a simple laboratory electrochemical method of surface nano-treatment of aluminum to industrial applications. The electrochemical method has been applied to process 1050A aluminum. Surface nano-structuring has been achieved and resulted in the formation of an organized alumina nanotubes layer on commercial aluminum plates used as adherends for the manufacturing of aluminum single-lap adhesive joints. The mechanical properties of single-lap aluminum adhesive joints constructed with both non-anodized and anodized adherends were investigated and compared. Two types of epoxy resins were used to prove that the anodization of the adherends is equally effective, independently of the adhesives’ type. Furthermore, three overlap lengths were used (7, 10, and 25 mm) to study the effect of the overlap length on the overall joint mechanical response. Results of both three-point bending and tensile–shear testing showed that there is a considerable improvement of the joints’ mechanical performance with the addition of the nanostructures, for all the overlap lengths. It was found that the anodization method greatly contributes to the strengthening of the joints, leading to a strength increase of up to 176% and 148% for the shear and three-point bending strength, respectively.

The aim of the present study is to examine and compare the thermal and mechanical properties of epoxy resin/TiO2 particle microcomposites (0.2 μm) and nanocomposites (21 nm). Composite materials consisting of epoxy resin reinforced with different amounts of TiO2 microparticles (1, 5, 10, 15, and 20% wt) and TiO2 nanoparticles (0.5%, 1%, 3%wt) were prepared. The thermal and mechanical properties of the manufactured composites were investigated and compared through differential scanning calorimetry (DSC) and three‐point bending tests (3PB). Lipatov's Theory was then applied on the DSC results, thus leading to the calculation of the particle‐matrix interphase thickness which was correlated to experimental findings. The glass transition temperature (Tg) of the materials was obtained and the effect of the grain size on the measured Tg values was investigated. The data obtained from DSC tests for both micro‐ and nanoinclusions when normalized with respect to the specific surface area of the particles, resulted in a single continuous curve describing the normalized phase transition enthalpy variation with filler weight fraction. POLYM. ENG. SCI., 58:1146–1154, 2018. © 2017 Society of Plastics Engineers