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Glass fiber epoxy composites are widely used in industries. Liquid epoxidized natural rubber was added to epoxy as the matrix for a fiber-reinforced composite in order to improve its mechanical properties whilst E-glass fiber was used as the composite reinforcement. Flexural test, Izod impact test, tensile test, thermogravimetric analysis, and scanning electron microscopy were performed to investigate the effect of liquid epoxidized natural rubber addition and glass fiber loadings on the mechanical properties of the composite. It was observed that the flexural strength and flexural modulus of the samples increased with increasing glass fiber percentage with 9% as the maximum weight percentage recorded. The tensile strength and Young’s modulus increased with increasing glass fiber content until it reached the maximum value at 9 wt% of glass fiber. The same trend was observed with the impact value of the samples. All the tests were conducted for the composite with and without liquid epoxidized natural rubber addition. The presence of liquid epoxidized natural rubber improved the mechanical properties of the composites due to the plasticizing effect of the rubber particles in the matrix. Thermogravimetric analysis revealed the thermal stability of the composites whilst the scanning electron microscopy shows a heterogeneous dispersed phase of morphology. There was poor adhesion between the matrix polymer and glass fibers due to the use of untreated glass fibers. [ABSTRACT FROM PUBLISHER]

An effort was made to study the effect of hygrothermal ageing at varying intervals of time on the interphase of the fiber-reinforced polymer composites. Silane-coated glass fibers and epoxy as matrix were used to fabricate the micro-composite. Absorbance peaks of OH stretching bands were focused to study the curing mechanism of epoxy matrix and effect of hygrothermal exposure at the interphase of the micro-composite by Fourier transform infrared (FTIR) imaging. The differential scanning calorimeteric (DSC) was carried out to monitor the glass transition temperature of hygrothermally aged samples after each interval. The FTIR results shows existence of gradient in degree of curing from the interphase to the bulk matrix and with the increase in ageing time the water absorption increases at the interphase leading to improvement in the adhesion initially, as it is reflected in the results obtained with DSC analysis, i.e., increases in glass transition temperature with the ageing time was reported. Obtained improved results may be attributed to moisture induced additional ring opening polymerization of epoxide molecule and/or formation of strong hydrogen double bonds with the epoxy matrix by water molecule. Microstructural analysis was done for hygrothermally treated samples by scanning electron microscope (SEM). [ABSTRACT FROM AUTHOR]

This study reports the method of recovery of glass fibers from glass/epoxy composites through the solvent method. It is possible to decompose epoxy resin with a yield of more than 99 wt% soluble products in a nitric acid solution (8 M) at 90°C for 5 h. The decomposition rate of epoxy resin increases with an increase in temperature and concentration of acid solution. The glass fibers can be recovered with very little contamination and they have a tensile strength reduction of 3.5% under decomposition conditions of T=70°C, t=250h, C=6M and α=6g/100mL. These fibers can be used as reinforcement to prepare new composites. The interlaminar shear strength (ILSS) of recovered short fiber-reinforced composites produce strength reductions of only 2.5% compared with pristine composites. [ABSTRACT FROM AUTHOR]

Polymer matrix composites using renewable resources are currently of great interest. A novel soy-based resin system for pultrusion was synthesized at University of Missouri-Rolla (UMR). Due to relatively low reactivity of soy-based resin and short curing time of pultrusion, it is important to set up the process parameters properly in order to obtain a high quality pultruded product. In the present work, a combination of experimental and numerical methods is used to investigate the effect of pultrusion process variables on the cure of composites. A mathematical model has been developed and implemented in the commercial ABAQUS finite element package to predict the temperature and degree of cure of soy-based composites. The kinetic parameters of the soy-based epoxy resins are obtained from a differential scanning calorimeter (DSC). Glass fiber-reinforced composite samples are manufactured using a pultrusion machine. For experimental verification, an online monitoring system is used to measure the temperature profiles inside the die. The degrees of cure of pultruded soy-based composites are measured by DSC. The experimental findings are in good agreement with the finite element prediction. The results indicate that the novel soy-based epoxy resin system is suitable for application in the pultrusion process. [ABSTRACT FROM AUTHOR]