The primary factors affecting the impact damage tolerance of composite materials are the characteristics of the resin and the fiber, the fiber/matrix interface and the reinforcement architecture. The resin and textile reinforcement are the topics of this work. A thermoplastic epoxy resin (TP) was developed coupling the advantages of thermoset and thermoplastic resins. It has the workability of thermoset resins and the formability and recyclability of thermoplastic systems. In previous study, this thermoplastic epoxy was adopted for manufacturing textile carbon fiber composites. The effect of the weight-average molecular weight (Mw) was investigated, and results highlighted improved tensile strength, longer tensile-tensile fatigue life, and enhanced fracture toughness (mode I and II). The fracture toughness driven by the properties of the TP epoxy matrix could suggest a better impact performance. Over the past decades, to enhance the impact behavior of composite materials, research efforts were dedicated to improving the toughness of resins by dispersion of nano- or micro- sized fillers. This strategy was adopted in the present work. The highly polymerized thermoplastic epoxy matrix was modified with submicron diameter glass fibers (0.1% and 0.3% in weight of resin), and then adopted as matrix of woven carbon fiber composites. For the sake of comparison, a thermoset epoxy system (TS) was considered. Drop weight impact test was performed, and the impact damage extension was observed by laser microscope morphology, thermal measurements, and X-ray μ-CT. The residual mechanical strength after impact was measured by compression tests. Overall, the high Mw TP composites, unmodified and 0.3% modified matrices, had the better impact performance with smooth and more ‘ductile’ post peak impact behavior and lower level of absorbed energy than the TS counterparts. The damage distribution confirmed the better damage tolerance of the 0.3% modified high Mw TP composites, having: a reduced dent depth, an almost uniform distribution of the surface temperature, a lower crack density and interlaminar delamination, and shorter transverse crack paths thought the thickness. This was the effect of the matrix toughness and the bridging action of micro glass fibers. As for the retention of compressive strength, the high Mw TP composites, modified with 0.3% of submicron diameter glass fibers, significantly suppressed the reduction of strength after impact (retention of about 91%).

CARBON TEXTILE REINFORCED HIGHLY POLYMERIZED THERMOPLASTIC EPOXY: EFFECT OF SUBMICRON GLASS FIBRES ON THE IMPACT RESPONSE

Carvelli V.;
2022-01-01

Abstract

The primary factors affecting the impact damage tolerance of composite materials are the characteristics of the resin and the fiber, the fiber/matrix interface and the reinforcement architecture. The resin and textile reinforcement are the topics of this work. A thermoplastic epoxy resin (TP) was developed coupling the advantages of thermoset and thermoplastic resins. It has the workability of thermoset resins and the formability and recyclability of thermoplastic systems. In previous study, this thermoplastic epoxy was adopted for manufacturing textile carbon fiber composites. The effect of the weight-average molecular weight (Mw) was investigated, and results highlighted improved tensile strength, longer tensile-tensile fatigue life, and enhanced fracture toughness (mode I and II). The fracture toughness driven by the properties of the TP epoxy matrix could suggest a better impact performance. Over the past decades, to enhance the impact behavior of composite materials, research efforts were dedicated to improving the toughness of resins by dispersion of nano- or micro- sized fillers. This strategy was adopted in the present work. The highly polymerized thermoplastic epoxy matrix was modified with submicron diameter glass fibers (0.1% and 0.3% in weight of resin), and then adopted as matrix of woven carbon fiber composites. For the sake of comparison, a thermoset epoxy system (TS) was considered. Drop weight impact test was performed, and the impact damage extension was observed by laser microscope morphology, thermal measurements, and X-ray μ-CT. The residual mechanical strength after impact was measured by compression tests. Overall, the high Mw TP composites, unmodified and 0.3% modified matrices, had the better impact performance with smooth and more ‘ductile’ post peak impact behavior and lower level of absorbed energy than the TS counterparts. The damage distribution confirmed the better damage tolerance of the 0.3% modified high Mw TP composites, having: a reduced dent depth, an almost uniform distribution of the surface temperature, a lower crack density and interlaminar delamination, and shorter transverse crack paths thought the thickness. This was the effect of the matrix toughness and the bridging action of micro glass fibers. As for the retention of compressive strength, the high Mw TP composites, modified with 0.3% of submicron diameter glass fibers, significantly suppressed the reduction of strength after impact (retention of about 91%).
2022
highly polymerized thermoplastic epoxy, submicron diameter glass fibers, woven carbon fiber composites, impact,
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1224192
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