RESUMO
The effects of thermal aging at 85~145 °C in air on the tensile and flexural mechanical properties of 20% glass fiber (GF)-reinforced commercial grade polybutylene terephthalate (PBT) composites were studied. The results showed that as the aging temperature increased, the tensile and flexural strength of the GF/PBT composites significantly decreased. However, the elastic modulus of the composites was almost independent of aging. As the aging temperature increased, the separation between GF and the PBT matrix became more pronounced, and the fibers exposed on the surface of the matrix became clearer and smoother, indicating a decrease in interfacial adhesion between the PBT matrix and GF. The reason for this decrease in strength and brittle fracture of composites is the interface damage between the GF and PBT matrix caused by the difference in their thermal expansion coefficients during thermal aging.
RESUMO
In this paper, mechanical properties of the diglycidyl ether of bisphenol A epoxy resin (EP) reinforced with a 20% fiber glass (GF) with layered structure after high temperature aging are studied. Tensile and flexural stress-strain curves of the GF/EP composite after aging tests in the temperature range of 85-145 °C in air were measured. Tensile and flexural strength demonstrate gradual decrease with the increase in the aging temperature. The failure mechanism at the micro scale is studied by the scanning electron microscopy. A separation of the GFs and EP matrix and evident pullout of the GFs are observed. Degradation of the mechanical properties is explained by a cross-linking and chain scission of the initial molecular structure of the composite and decrease in the interfacial adhesion force between GFs and EP matrix caused by oxidation of the EP matrix and difference of the GF and EP coefficients of thermal expansion.
RESUMO
In this article, the thermal aging behavior of polyphenylene sulfide (PPS) composites, reinforced by 20% glass fibers (GFs), in thermal aging temperatures ranging from 85 to 145 °C was studied. Tensile and bending properties and color changes in the thermally aged samples were investigated. The results showed that thermal aging at this temperature range resulted in the degradation of mechanical properties. Both the tensile and flexural strength of the GF/PPS composites were significantly reduced after thermal aging at 145 °C. Decreased strength and brittle fracture were observed because thermal aging at high temperatures resulted in the deterioration of the interfaces between the GFs and PPS matrix. The degradation of the mechanical properties of the composite samples can be reflected by the color change, which means that the mechanical properties of the GF/PPS composite samples under thermal aging are predictable using color change analysis.
RESUMO
Thermal aging of polymer matrix composites exert significant influence on their properties and applications. This paper studied the color changes and mechanical properties of glass fiber reinforced polycarbonate (GF-PC) composites after aging at different temperatures, and the correlation between the trend of color changes and mechanical properties after aging was discussed. The GF-PC composites were aged at 85 °C, 100 °C, 115 °C, 130 °C and 145 °C, respectively. Thereafter, CIELAB colors were used to characterize the color changes of the composites after aging. Tensile and three-point bending tests were carried out to determine the mechanical properties of the composites. According to the values of CIELAB color, the color changes and the color difference (ΔE) of the GF-PC composites after aging were calculated, which showed that color of the GF-PC composite aged at 100 °C changed the most. The color changes of the composites after aging mainly comes from the change of brightness (L value), which was 25.067 for the Raw GF-PC composite. When the aging temperature increased from 85 °C to 100 °C, the brightness of the composites also increased, but decreased when the aging temperature is above 100 °C and continues to rise. Coincidentally, the trend of the mechanical properties of GF-PC composites is closely associated with color changes in the aging temperature range of 85 °C to 145 °C. The tensile and flexural strength of the composites reached the maximum value 72 MPa and 131 MPa, respectively, after aged at 100 °C. It can be speculated that the brightness of the GF-PC composites correlates with trends observed in its tensile strength and bending strength.
RESUMO
This research study is aimed at evaluating the mechanical characteristics in terms of tensile strength and flexural strength of glass fiber reinforced Polyetherimide (GF/PEI) under different thermal aging. Tensile testing and bending testing were performed on the thermally aged polyetherimide composites. The mechanical properties of the thermally aged samples were also correlated with their color difference. The experimental results showed that both the tensile strength and flexural strength of the GF/PEI composite samples decreased with increasing aging temperature. However, the elastic modulus of the composite samples is nearly independent on the thermal aging. The thermally aged samples exhibited brittle fracture, resulting in low strength and low ductility. The loss in strength after thermal aging could be also linked to the change of their color difference, which can indirectly reflect the change of the strength for the composites after thermal aging.
