Environmental Effects on Mechanical Properties of Composites Materials – A New Recommended Practice
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Andreas ECHTERMEYER (NORWAY), Ramin MOSLEMIAN , Philippe NOURY (NORWAY)Abstract :
Composite materials provide an appealing substitute for metals, boasting excellent environmental resistance and a superior stiffness-to-weight ratio. These distinctive qualities yield significant advantages in subsea structures, pipelines, and renewable energy applications, addressing challenges like weight and corrosion. Nevertheless, the industry's adoption of composites has been hindered for years by intricate qualification requirements in design codes concerning resistance to challenging environments, high testing costs, and long-term efforts. The recently introduced DNV Recommended Practice (RP) addresses this critical challenge faced by several industries – The environmental exposure and degradation of composite materials.
Models and assessment methodologies, supported by experiments, have been developed to enhance understanding and address the effects of fluid exposure and temperature in the thermoset and thermoplastic composite designs. Experimental, analytical, numerical and semi-empirical methods have been developed to assess chemical interactions with liquids and gas and to obtain Arrhenius-based Time-Temperature-Saturation-Superposition-dependent polymer and composite properties, incorporating the impact of chemical and mechanical interactions.
This Recommended Practice provides testing procedures for assessing, first, the occurrence of chemical degradation. Chemical degradation refers to permanent alterations in the polymer resulting from absorbed fluids. Other reversible interactions associated with swelling are addressed separately. If a material exhibits chemical reactions, its properties should be evaluated after undergoing preconditioning to simulate the chemical degradation that may occur over its lifetime. Methods are given for polymers to obtain stiffness and strength over the design lifetime. They are based on testing and interpolation. Specific confirmation testing is necessary to validate the applicability of these methods to the polymer in question. Cyclic fatigue and creep rupture are included. The methods cover applications below and above the glass transition temperature. The methods and procedures are detailed to ensure the applicability of the recommendations to specific material systems and have clear boundaries, such as long-term data interpolation and extrapolation.
Possible avenues for additional research investigations involve validating the methodologies on elastomers, exploring cyclic fatigue in different thermoplastic materials, and investigating partially saturated samples.
A robust framework of unified methods has been developed to reliably determine the mechanical properties of polymers and composites across various environmental conditions. This development will facilitate the swift qualification of composite materials and new composite technologies, which are crucial for high-risk transport and storage assets and the broader energy transition.
Models and assessment methodologies, supported by experiments, have been developed to enhance understanding and address the effects of fluid exposure and temperature in the thermoset and thermoplastic composite designs. Experimental, analytical, numerical and semi-empirical methods have been developed to assess chemical interactions with liquids and gas and to obtain Arrhenius-based Time-Temperature-Saturation-Superposition-dependent polymer and composite properties, incorporating the impact of chemical and mechanical interactions.
This Recommended Practice provides testing procedures for assessing, first, the occurrence of chemical degradation. Chemical degradation refers to permanent alterations in the polymer resulting from absorbed fluids. Other reversible interactions associated with swelling are addressed separately. If a material exhibits chemical reactions, its properties should be evaluated after undergoing preconditioning to simulate the chemical degradation that may occur over its lifetime. Methods are given for polymers to obtain stiffness and strength over the design lifetime. They are based on testing and interpolation. Specific confirmation testing is necessary to validate the applicability of these methods to the polymer in question. Cyclic fatigue and creep rupture are included. The methods cover applications below and above the glass transition temperature. The methods and procedures are detailed to ensure the applicability of the recommendations to specific material systems and have clear boundaries, such as long-term data interpolation and extrapolation.
Possible avenues for additional research investigations involve validating the methodologies on elastomers, exploring cyclic fatigue in different thermoplastic materials, and investigating partially saturated samples.
A robust framework of unified methods has been developed to reliably determine the mechanical properties of polymers and composites across various environmental conditions. This development will facilitate the swift qualification of composite materials and new composite technologies, which are crucial for high-risk transport and storage assets and the broader energy transition.