In the framework of green materials, in recent years, natural fiber composites attracted great attention of academia and industry. Their mechanical and tribological characteristics, such as high strength, elasticity, friction, and wear resistance, make them suitable for a wide range of industrial applications in which issues regarding a large amount of disposal are to be considered since their environmental friendliness gives them an advantage over conventional synthetic materials. Based on the recent and relevant investigations found in the scientific literature, an overview focused on the tribological characteristics of composite materials reinforced with different types of natural fibers is presented. The aim is to introduce the reader to the issues, exploring the actual knowledge of the friction and wear characteristics of the composites under the influence of different operating parameters, as well as the chemical treatment of fibers. The main experimental tribological techniques and the main used apparatus are also discussed, with the aim of highlighting the most appropriate future research directions to achieve a complete framework on the tribological behavior of many possible natural fiber composite materials.

This paper presents tribological research of an abaca fiber-reinforced epoxy composite material, analyzing fiber orientation and its effect on the tribological performances of the composite. The extremely low viscosity epoxy resin reinforced with NaOH-treated long abaca fibers is investigated under the different operating conditions. The unidirectional abaca fibers reinforced the epoxy resin and formed composite specimens with fibers in three directions, parallel (P-O), anti-parallel (AP-O) and normal (N-O), while keeping the sliding direction. The specimens were fabricated using fiber volume fractions of 10 vol%, 20 vol% and 30 vol% using the vacuum infusion technique. The block-on-disc (BOD) apparatus has been used to exhibit the tribological tests. Normal loads of 35 N and 45 N have been used for testing purposes. The experimental results indicated that the presence of abaca fiber significantly improved the wear characteristics of the matrix. An increased coefficient of friction was observed in samples with anti-parallel-oriented fibers at an applied load of 35 N. The conducted research shows that the use of abaca fibers as fillers could improve the tribological characteristics of the epoxy resin-based composite material.

Hydraulic dilatation is a novel method of cervical dilatation that is based on continuous controllable dilatation (CCBD) by the pumping of fluid into the balloon extension of the system. The main advantage of this procedure is that it allows control of and insight into the process of cervical dilatation. For the purposes of our research, we created a new and upgraded system for CCBD which consists of a programmed hydrostatic pump connected to a balloon extension. With regard to our aim to precisely measure and determine the location of the cervical resistance, we placed two pressure-measuring films, one on the top and one on the bottom of the balloon extension. This study included 42 patients in whom cervical resistance was measured before suction curettage. Cervical dilatation and measurement of cervical resistance were successful in all patients. The analysis of the pressure-measuring films showed that the points of highest resistance were located in the zone of the internal cervical os and that these values were much higher than those in the zone of the external cervical os (0.402 versus 0.264 MPa at the upper pressure-sensitive film; 0.387 versus 0.243 MPa at the lower pressure-sensitive film). This study also showed that an increase in cervical resistance in the zone of the internal cervical os was followed by an increase in cervical resistance in the zone of the external cervical os. During CCBD, the internal cervical os is the centre of cervical resistance, and the values do not decline with the number of miscarriages or the number of previous births. ISRCTN Registry identifier: ISRCTN30949871 . Date of registration: 13 May 2015.