Impact and Implication of Thermal Conditioning on the Mechanical behavior of FRP Composites

Abstract

Fiber reinforced composites are used extensively on a very large scale. They are subject to change in temperature and loading conditions constantly. In the experimental study, we have tried to assess the impact of temperature and conditioning time on the mechanical behaviour of glass fiber reinforced composites. Interface is the most significant part of composite structure which regulates the load transfer from matrix to fiber. Its strength is measured in terms of ILSS (Inter Laminar Shear Strength). Short beam shear tests are done at ambient and 60⁰C for conditioning times 30 minutes, 1 hour and 3 hours .The results show that at high temperature, there is initial increase in the strength of interface up to 30 minutes followed by weakening as conditioning time increases to 1 hour. This again is followed by strengthening of the interface as conditioning time extends to 3 hours. Understanding the effect of conditioning time might help us in optimization of the mechanical properties. Composite material may contain randomly spaced microvoids, incipient damage sites and microcracks with statistically distributed sizes and directions. Therefore, the local strength in the material varies in a random fashion. The failure location as well as degree of damage induced in the material will also vary in an unpredictable mode. The fractured surfaces are photographed by SEM analysis and studied. As temperature increases, the mode of failure approaches matrix cracking, fiber breakage and debonding. Each test is carried out at six different crosshead speeds, 5mm /min, 10mm/min, 50mm/min, 100mm/min, 200mm/min, and 500mm/min. ILSS decreases as crosshead speed is increased. FTIR analysis of composite specimens was carried out to interpret the reaction between matrix and fiber at the interface. DSC analysis was done to understand the deflection of glass transition temperature with the change in temperature and conditioning time. There are a lot of conflicts over this subject and this study has tried to highlight the major factors which need to be focussed upon for further improvement in the field of composites.