Effects of In-Service Environments and Hygrothermal Ageing on Tensile Response of Structural Biocomposites: A Comparative Study of Flax and Glass Epoxy Composites
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Yasmine MOSLEH (NETHERLANDS), Valentin PERRUCHOUD (NETHERLANDS), René ALDERLIESTEN (NETHERLANDS)Abstract :
Growing concerns about climate change and the profound influence of large-scale engineering structures on global CO2 emissions prompt the exploration of sustainable construction materials. Within the realm of Fibre Reinforced Polymer (FRP) composites, the integration of high-performance natural fibres, such as flax, presents a promising alternative to replace synthetic counterparts, yielding bio-composites that are both sustainable and high-performing. However, the effects of exposure to diverse outdoor environmental conditions on the short and long-term mechanical behaviour of flax FRP composites are not well understood yet and may have a significant impact on structural durability and safety.
Unlike uniform and isotropic synthetic fibres like glass, flax fibres exhibit a complex, multiscale, and anisotropic microstructure resulting in a bilinear mechanical behaviour comprised of both elastic and inelastic regions. Additionally, flax fibres are inherently hygroscopic, undergoing dimensional changes in response to variations in environmental relative humidity. As a result, flax FRP composites exposed to various hygrothermal conditions are susceptible to moisture-induced internal stresses, cracking, and mechanical properties changes.
To date, a thorough understanding of hygrothermal effects on the mechanical response of flax FRP composites is still lacking. This knowledge is pivotal for the realisation of large-scale structural elements in biocomposites exposed to outdoor environments. Important for accurate service-life modeling of biocomposites, hygrothermal effects have to be accounted for their immediate effect on the materials in specific operating environment and also for their effect on the long-term material durability (environmental ageing and fatigue) that can be challenged with seasonal cycles.
This study examines hygrothermal effects on the quasi-static tensile response of flax and glass FRP composites with the goal of establishing crucial groundwork for incorporating hygrothermal considerations into structural design and future standards with the use of knock-down factors. In this research, experiments are performed on flax and glass FRP composites with a cross-ply (0°/90°) and angle ply (±45°) laminate architectures. To test the long-term environmental effects, specimens are aged in a climate chamber and subjected to moisture cycles between 30% and 90% relative humidity (RH) prior to quasi-static tensile loading occurring at 20°C and 50% RH. To test the immediate hygrothermal effects, a climate chamber enclosing the tensile testing area is used to control the environment which is set to conditions ranging from -20°C to 50°C and from 50% RH to 90% RH. Additionally, optical microscopy is used to analyse damage patterns induced by environmental ageing, mechanical loading, and their combined effects.
Unlike uniform and isotropic synthetic fibres like glass, flax fibres exhibit a complex, multiscale, and anisotropic microstructure resulting in a bilinear mechanical behaviour comprised of both elastic and inelastic regions. Additionally, flax fibres are inherently hygroscopic, undergoing dimensional changes in response to variations in environmental relative humidity. As a result, flax FRP composites exposed to various hygrothermal conditions are susceptible to moisture-induced internal stresses, cracking, and mechanical properties changes.
To date, a thorough understanding of hygrothermal effects on the mechanical response of flax FRP composites is still lacking. This knowledge is pivotal for the realisation of large-scale structural elements in biocomposites exposed to outdoor environments. Important for accurate service-life modeling of biocomposites, hygrothermal effects have to be accounted for their immediate effect on the materials in specific operating environment and also for their effect on the long-term material durability (environmental ageing and fatigue) that can be challenged with seasonal cycles.
This study examines hygrothermal effects on the quasi-static tensile response of flax and glass FRP composites with the goal of establishing crucial groundwork for incorporating hygrothermal considerations into structural design and future standards with the use of knock-down factors. In this research, experiments are performed on flax and glass FRP composites with a cross-ply (0°/90°) and angle ply (±45°) laminate architectures. To test the long-term environmental effects, specimens are aged in a climate chamber and subjected to moisture cycles between 30% and 90% relative humidity (RH) prior to quasi-static tensile loading occurring at 20°C and 50% RH. To test the immediate hygrothermal effects, a climate chamber enclosing the tensile testing area is used to control the environment which is set to conditions ranging from -20°C to 50°C and from 50% RH to 90% RH. Additionally, optical microscopy is used to analyse damage patterns induced by environmental ageing, mechanical loading, and their combined effects.