Abstract
Fiber-reinforced polymer composite materials have become materials of choice for manufacturing application due to their high specific stiffness, strength and fatigue life, low density and thermal expansion coefficient. However, there are some types of defects such as porosity that form during the manufacturing processes of composites and alter their mechanical behavior and material properties. In his study, hand lay-up was conducted to fabricate samples of carbon fiber-reinforced polymer composites with three different vacuum levels in order to vary porosity content. Nondestructive evaluation, destructive techniques and mechanical testing were conducted. Nondestructive evaluation results showed the trend in percentages of porosity through-thickness. Serial sectioning images revealed significant details about the composite’s internal structure such as the volume, morphology and distribution of porosity. Mechanical testing results showed that porosity led to a decrease in both Mode I static interlaminar fracture toughness and Mode I cyclic strain energy release rate fatigue life. The fractographic micrographs showed that porosity content increased as the vacuum decreased, and it drew a relationship between fracture mechanisms and mechanical properties of the composite under different modes of loading as a result of the porosity effects. Finally, in order to accurately quantify porosity percentages included in the samples of different vacuum levels, a comparison was made between the parameters and percentages resulted from the nondestructive evaluation and mechanical testing and the features resulted from fractography and serial sectioning.
Highlights
Composite materials are manufactured from two or more materials to take advantage of desirable characteristics of the components
In order to accurately quantify porosity percentages included in the samples of different vacuum levels, a comparison was made between the parameters and percentages resulted from the nondestructive evaluation and mechanical testing and the features resulted from fractography and serial sectioning
Nondestructive evaluation methods gave the trend in discontinuities or density variations that can be related to the porosity content
Summary
Composite materials are manufactured from two or more materials to take advantage of desirable characteristics of the components. Composites usually consist of a reinforcing agent (fiber) and a compatible resin binder (matrix) to obtain desired properties. Advanced composites can be divided into laminates and sandwiches [1]. The laminates are layers or plies of composite materials bonded together, whereas, the sandwich is a multiple-layer composite structure consisting of a low-density core between thin laminate faces (skins) of composite materials. The two major techniques to fabricate blades composites are resin infusion and hand lay-up. Several types of manufacturing defects might emerge in the composite such as porosity, fiber waviness, ply waviness, debonding between the fibers and the matrix and inclusions. Defects can lead to severe degradation in the composite properties [1]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
