تعیین حد فرسودگی برای کامپوزیت
Abstract
1-Introduction
2-Self-Heating Methodology
3-Experimentation
4-Results and Discussion
5-Conclusion
Acknowledgements
Reference
Abstract
The main objective of this paper is to present three indicators to determine the fatigue limit of woven carbon-fiber epoxy-matrix laminates using the Self-Heating test method. The approach adopted in the self-heating methodology consists usually in plotting the heat transfer indicator values versus the maximum stress values. This plot is named the self-heating curve and from the profile of the self-heating curve, one can identify the fatigue limit. During the self-heating experiments, the temperature of the specimen increases with the number of applied cycles and then stabilizes after a certain number of cycles. In this study a novel “peak-temperature point” approach was identified as the most suitable methodology to determine the fatigue limit for a class of composite materials. The paper also sheds some light on how a suitable approach can be chosen to uphold the economic aspect of the self-heating methodology. The purpose of the present paper is to validate this approach for an impacted laminate.
Introduction
CFRP structures have mostly replaced aluminium and steel, primarily due to their high strength and high stiffness to weight ratios, which are more than five times greater than conventional structural materials. Therefore, it is of utmost important for the scientific society to clearly understand the mechanical properties of these fibre reinforced composite materials, and especially the fatigue properties. CFRP composites are highly anisotropic and hence have complex failure mechanisms. Wöhler curves have been used to estimate the fatigue life of metals as well as composite materials [1-4]. The determination of the fatigue limit of materials is mostly time consuming and expensive. To have a quick determination of fatigue limit of materials, a quite new methodology named the SelfHeating methodology was adopted by several researchers for metals [5-9] and composites [10-11]. This methodology has been proven successful in evaluating the fatigue limit of unidirectional and woven CFRP materials without any inherent flaws. The fatigue experiments based on the self-heating methodology take only a couple of hours (maximum of one day) in comparison to the conventional fatigue tests which takes months to produce results.