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Environmental Effects on Composite Materials
(Sponsored by DoD)
Felipe J. Acosta (PI),
Miguel A. Pando (co-PI), and Luis A. Godoy (co-PI)
2006-2008

Summary

This proposal addresses the identification of the fundamental damage degradation mechanisms of glass FRP composites at the constituent level (i.e. fiber, resin and their interface). The proposed research project will include an experimental and analytical component. The knowledge obtained from this experimental program will be used to develop a computational assessment tool based on micromechanics to serve as basis for life prediction models. Both experimental and computational work will be carried out in order to better understand and predict the long term behavior of FRP composite elements of any fiber lay-up. Some of the factors that contribute to the degradation of FRP composites over time include temperature, UV rays, moisture absorption, freeze-thaw cycles and load. The proposal is limited to moisture absorption (from fresh water) and how this affects the mechanical properties under different conditions of temperature and stress level. Experiments will be done through accelerated hygro-thermal conditions. Three basic configurations will be tested: resin-only panels, unidirectional FRP composite panels and cross-ply FRP composite panels. The specimens will be submerged in fresh water at different temperatures to obtain moisture diffusion properties as a function of water temperature. Mechanical properties (tension, impact and fatigue) of the panels will be tracked at different levels of moisture contents and time. Damage levels will be assessed using microscopy, DMA and TMA. The analytical model will be oriented to model the micromechanics of this problem. Two simultaneous processes will be taken into account: moisture migration and material degradation. The material degradation model will follow the mechanisms observed by other authors and the results of the experimental part of the research as it becomes available. A micromechanical approach will be undertaken using the nonlinear capabilities in the commercial finite element package of ABAQUS. Results from this project will provide better tools to incorporate degradation to composite materials. Results are of utility for not only civil applications, but also for applications of interest for the US Navy and Army, where composite materials have become key for many applications. Regarding the impact to the University of Puerto Rico, the activities from this work will promote involvement of underrepresented students and faculty in engineering fields and will be a key contribution to the development of the new graduate program in Material Science and Engineering.

 

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