Fiber-reinforced polymer composites are becoming suitable and substantial materials in the repair and replacement of conventional metallic materials because of their high strength and stiffness. These composites undergo various types of static and fatigue loads during service. One of the major tests that conventional and composite materials have to experience is fatigue test. It refers to the testing for the cyclic behavior of materials. Composite materials are different from metals, as they indicate a distinct behavior under fatigue loading. The fatigue damage and failure mechanisms are more intricate in composite materials than in metals in which a crack initiates and propagates up to fracture. In composite materials, several micro-cracks initiate at the primary stage of the fatigue growth, resulting in the initiation of various types of fatigue damage. Fiber volume fraction is an important parameter to describe a composite laminate. The fatigue strength increases with the increase of the fiber volume fraction to a certain level and then decreases because of the lack of enough resin to grip the fibers. The fatigue behavior of fiber-reinforced polymer composites depends on various factors, e.g., constituent materials, manufacturing process, hysteresis heating, fiber orientation, type of loading, interface properties, frequency, mean stress, environment. This review paper explores the effects of various parameters like fiber type, fiber orientation, fiber volume fraction, etc. on the fatigue behavior of fiber-reinforced polymer composites.

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Purpose The aim of this paper is to study the effect of deterministic roughness and small elastic deformation of surface on flow rates, load capacity and coefficient of friction in Rayleigh step bearing under thin film lubrication. Design/methodology/approach Reynolds equation, pressure-density relationship, pressure-viscosity relationship and film thickness equation are discretized using finite difference method. Progressive mesh densification (PMD) method is applied to solve the related equations iteratively. Findings The nature and shape of roughness play a significant role in pressure generation. It has been observed that square roughness dominates the pressure generation for all values of minimum film thickness. Deformation more than 100 nm in bounding surfaces influences the film formation and pressure distribution greatly. Divergent shapes of film thickness in step zone causes a delay of pressure growth and reduces the load capacity with decreasing film thickness. The optimum value of film thickness ratio and step ratios have been found out for the maximum load capacity and minimum coefficient of friction, which are notably influenced by elastic deformation of the surface. Practical implications It is expected that these findings will help in analysing the performance parameters of a Rayleigh step bearing under thin film lubrication more accurately. It will also help the designers, researchers and manufacturers of bearings. Originality/value Most of the previous studies have been limited to sinusoidal roughness and thick film lubrication in Rayleigh step bearing. Effect of small surface deformation due to generated pressure in thin film lubrication is significant, as it influences the performance parameters of the bearing. Different wave forms such as triangular, sawtooth, sinusoidal and square formed during finishing operations behaves differently in pressure generation. The analysis of combined effect of roughness and small surface deformation has been performed under thin film lubrication for Rayleigh step bearing using PMD as improved methods for direct iterative approach.

In this study, the effect of adding glass ionomer (GI) Restorative Cement (0−30 wt%) on the mechanical and thermo‐mechanical characterization of dental composite has been discussed. The characterization of dental composites was done by performing Fourier transform infrared spectroscopy, hardness test, compression test, flexural strength test, dynamic mechanical analysis (DMA), thermo gravimetric analysis (TGA). The finding of experiments indicated that the addition of 10 wt% of GI increased the water hardness, flexural strength and compressive strength by 88.48, 15.95, and 17.74%, respectively. DMA results revealed that the storage modulus was initially increased by 88% when GI was increased up to 20 wt%, however, further increase of GI up to 30 wt% resulted in decrease in the storage modulus by 16.4%. Also, loss modulus was increased by 41.6% when GI was increased by 10 wt%, however, it was further decreased by 2.94% and by 35.29% on addition of GI filler content up to 20 and 30 wt%, respectively. Incorporation of GI up to 10 wt% decreased the damping factor by 36.36% but further addition of GI up to 20 and 30 wt% increased the damping factor of dental composite by 14.2 and 50%. TGA indicated that thermal degradation temperature was increased with the addition of GI filler. POLYM. COMPOS., 40:3361–3367, 2019. © 2018 Society of Plastics Engineers

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