Three commercial epoxy diglycidylether of bisphenol-A (DGEBA) were used in this study namely Epiphen RE4020-DE 4020 (Bostik), Epoxy Resin C (R&G Gmbh Waldenbuch), and Epoxy Resin HT-2 (R&G Gmbh Waldenbuch). Epoxy resins are often used for the friction purpose but their friction resistance is quite low and it is thus necessary to enhance their friction resistance. In this paper it is shown how load, sliding velocity, and distance affect friction coefficient of epoxy resins.

This paper presents experimental results on the behavior of a class of glass fiber composites under low velocity impacts, in order to analyze their usage in designing low velocity impact-resistant components in car and marine industries. Also, a finite element model at the meso level (considering yarn as a compact, homogenous and isotropic material) was run with the help of Ansys Explicit Dynamics in order to point out the stages of the failure and the equivalent stress distribution on the main yarns in different layers of the composite. The composites were manufactured at laboratory scale via the laying-up and pressing method, using a quadriaxial glass fiber fabric (0°/+45°/90°/−45°) supplied by Castro Composites (Pontevedra, Spain) and an epoxy resin. The resin was a two-component resin (Biresin^® CR82 and hardener CH80-2) supplied by Sika Group (Bludenz, Austria). The mass ratio for the fabric and panel was kept in the range of 0.70–0.77. The variables for this research were as follows: the number of layers of glass fiber fabric, the impact velocity (2–4 m/s, corresponding to an impact energy of 11–45 J, respectively) and the diameter of the hemispherical impactor (Φ10 mm and Φ20 mm) made of hardened steel. The tests were performed on an Instron CEAST 9340 test machine, and at least three tests with close results are presented. We investigated the influence of the test parameters on the maximum force (F_max) measured during impact, the time to F_max and the duration of impact, t_f, all considered when the force is falling to zero again. Scanning electron microscopy and photography were used for discussing the failure processes at the fiber (micro) and panel (macro) level. At a velocity impact of 2 m/s (corresponding to an impact energy of 11 J), even the thinner panels (with two layers of quadriaxial glass fiber fabric, 1.64 mm thickness and a surface density of 3.51 kg/m²) had only partial penetration (damages on the panel face, without damage on panel back), but at a velocity impact of 4 m/s (corresponding to an impact energy of 45 J), only composite panels with six layers of quadriaxial fabric (5.25 mm thickness and a surface density of 9.89 kg/m²) presented back faces with only micro-exfoliated spots of the matrix for tests with both impactors. These results encourage the continuation of research on actual components for car and naval industries subjected to low velocity impacts.

The aim of this study is to point out the effect of L-lysine and L-isoleucine used as modifying agents for epoxy resins. The amino acids are largely used to turn the usual polymers in bio-compatible materials but they effect also other significant proprieties of formed materials. The general study developed in Polymer Composite Laboratory is focused on analysis of 14 amino acids used as modifying agents but the two above mentioned showed a special behaviour namely they re-crystalized during the polymerization of the matrix. The coefficient of friction was obtained through the calculation of friction torque measured with a loaded cell sensor. As far as we know, there is no report on the friction proprieties of amino acids modified epoxy resins.

Ferrites are generally used to obtain soft magnets for domestic or industrial applications but their use in this direction had generated an increasing interest in modifying the polymer properties by dispersing in their volume certain amounts of these ceramic compounds. The current study focused friction wear behaviour induced by the presence of nano-sized strontium ferrite and barium ferrite in an epoxy matrix. The wear behaviour of nanoferite modified epoxy resins tests were conducted on a pin-on-disc geometry. Three types of epoxy resins had been used with 5% weight ratio of each type of ferrite and 10% weight ratio when both ferrites were used.

This study investigates the impact behaviour of glass fiber epoxy composites with a focus on achieving enhanced safety. A drop weight impact test machine was used to perform a series of impact tests on the composite samples. Two different impactors as dimensions and three velocities were used to investigate the impact behavior of glass fiber epoxy composites. The study’s goal is to investigate the impact response of these composites and their potential for usage in impact protection applications. The study findings show that glass fiber epoxy composites have outstanding impact resistance properties, as well as high levels of the ability to absorb energy and withstand the initiation of damage. The findings suggest that both the impactor (as shape and dimensions) and the velocity of impact have a notable influence impact on the damage mechanisms and energy absorption capacity of the composite materials. The failure mechanisms detected in the composites were mostly delamination and fibre breakage.

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