Composite Material Durability Studies

🛩 CFRP Fatigue From an Aerostructures Perspective Many engineers still interpret CFRP fatigue using a metallic mindset. In aerostructures this approach is fundamentally incorrect. Fatigue in carbon fibre reinforced polymers is not governed by a single crack. Damage evolves through interacting mechanisms including matrix cracking, fibre matrix debonding, delamination growth, and finally fibre rupture. Because the governing mechanism changes with laminate architecture, fibre orientation, loading ratio, environment, and manufacturing quality, a single S–N curve cannot represent composite fatigue behaviour. In aerospace structures, durability is therefore controlled through strain based design, environmental allowables, and building block testing, rather than relying solely on phenomenological fatigue curves. 📎The attached PowerPoint presentation explains the governing mechanisms, influencing parameters, and the aerospace design perspective in detail. #AerospaceEngineering #CompositeStructures #CFRP #Fatigue #StructuralEngineering #Aerostructures #MaterialsEngineering #CompositeMaterials #FractureMechanics #AircraftStructures

Happy to share our latest publication! Our interdisciplinary team explored the long-term durability, environmental impact, and biological receptivity of three cementitious materials—Ordinary Portland Cement (OPC), Alkali-Activated Material (AAM), and Recreated Roman Cement (RRC)—under natural seawater exposure for one year. https://lnkd.in/gpsxnfsV  Key Findings: * AAM had the lowest carbon footprint (72% reduction vs. OPC) but suffered from early-age shrinkage cracks, highlighting the importance of selecting appropriate activators and precursors. * OPC maintained the highest compressive strength (70 MPa) but exhibited full-depth cracking and the highest CO₂ emissions. * RRC demonstrated good durability, with no formation of harmful sulfate-bearing phases, and supported oyster growth due to its lower pH and porous structure. This work highlights the potential of sustainable binders like RRC and AAM for marine infrastructure and artificial reef development—balancing durability, carbon reduction, and ecological enhancement. 📌Note: This study covers only one year of exposure. Fortunately, we still have samples at the exposure sites and plan to conduct further evaluations after 3 or 5 years. Grateful to our team and collaborators at UT Arlington and Texas A&M AgriLife Research: Adhora Tahsin, PhD, EIT Ishrat Baki Borno Nishad Ahmed Nithya Nair, Christopher Hollenbeck, and the sponsor of the work: Defense Advanced Research Projects Agency (DARPA) 📩 For more info or collaboration, feel free to reach out!

Appropriately designed and processed fiber reinforced polymer composites provide fiber reinforced polymer (FRP) composites provide significant advantages over conventional materials in civil, offshore, and marine, infrastructure applications. Their efficacy over long periods of exposure to the environment depends in part on moisture uptake characteristics and effects thereof. The recently published paper co-authored with Stephanie Svetlik-Haley in the Journal of Composite Materials provides a comprehensive study and assessment of moisture uptake and kinetics of a pultruded GFRP composite exposed to a range of humidity levels and immersion over temperatures between 20°C and 80°C, as a means of providing a basic foundation for the further determination of long term durability. The moisture uptake regimes were noted to deviate substantially from the simplistic Fickian response generally assumed of an initial linear regime followed by attainment of an equilibrium level of uptake. Four different models were used to describe the response and the two-stage structural modification model which incorporates both an initial diffusion dominated regime and a subsequent slower relaxation/deterioration dominated regime was seen to most accurately describe the range of profiles obtained over all the exposure conditions considered in the investigation. While immersion is often used in laboratory tests to represent the humidity in the field it is shown that the results of exposure to 99% RH and of immersion even at elevated temperature levels of the former are significantly different with parameters from immersion levels being lower, emphasizing the erroneous assumption of equivalence. While increases in temperature can be used as a means of accelerating response in time, it is noted that the use of the higher levels of temperature although still significantly below the unexposed glass transition level, do suggest changes in mechanisms within the bulk polymer and the composite as seen through shifts in the shape of the uptake profile and in kinetics of uptake as well as the resulting characteristics of diffusion coefficient, transition and maximum uptake levels, and parameters of the second stage, indicating a need for greater care in assuming the validity of time-temperature superposition over large ranges of temperature and/or humidity levels. #FRP #Durability #Composites #Moisture #Infrastructure #Marine #Offshore #GFRP #Diffusion