The high chemical resistance of the advanced thermoplastic polymers, such as polyether ether ketone (PEEK), polystyrene (PS), or polyamide (PA), makes methods of the composites’ composition evaluation based on chemical etching difficult and tedious. Wider application of the composites with thermoplastic matrix creates a need to find more capable, faster, and easier method of fiber and void content determination. Thermogravimetric analysis (TGA) is known to be one of the most promising candidates. Numerous reports have shown that TGA could be successfully applied for glass-reinforced composites. In this study, carbon fiber/PEEK composite was investigated. Initial tests showed that a simple method based on total burn-up of the matrix cannot be used for such advanced composites due to the high thermal resistance of PEEK. Tests carried with various parameters and microscopic investigation of the degradation process allowed to propose an analysis method that can give a satisfactory outcome. Results obtained with carbon fiber/PEEK composite using TGA-based method matched those obtained by chemical etching. Supplementary investigation of PA-based and epoxy resin composites showed the applicability of the method to a wider group of both thermoplastics- and thermoset-based carbon fiber–reinforced composites.

The influence of hot pressing conditions on mechanical properties of nickel aluminide/alumina composite has been investigated in the present paper. In particular, effect of the process parameters, viz. compacting pressure, sintering temperature and sintering time on the evolution of density, elastic constants and tensile strength properties of the intermetallic-ceramic composite has been studied. Elastic constants, the Young's modulus and Poisson's ratio, have been evaluated using an ultrasonic testing method, and the tensile strength has been determined by a Brazilian-type splitting test. Microscopic observations of microstructure evolution complemented the experimental procedure. Experimental results have been confronted with theoretical models showing a good agreement between the data compared.

Composites made of a biodegradable polymer, e.g., polylactic acid (PLA) and hydroxyapatite nanoparticles (HAP NPs) are promising orthopedic materials. There is a particular need for biodegradable hybrid nanocomposites with strong mechanical properties. However, obtaining such composites is challenging, since nanoparticles tend to agglomerate, and it is difficult to achieve good bonding between the hydrophilic ceramic and the hydrophobic polymer. This paper describes a two-step technology for obtaining a ceramic matrix composite. The first step is the preparation of composite granules. The granules are obtained by infiltration of porous granules of HAP NPs with PLA through high-pressure infiltration. The homogeneous ceramic-polymer granules are 80 μm in diameter, and the composite granules are 80 wt% HAP NPs. The second step is consolidation of the granules using high pressure. This is performed in three variants: Uniaxial pressing with the pressure of up to 1000 MPa at room temperature, warm isostatic compaction (75 MPa at 155 °C), and a combination of the two methods. The combined methods result in the highest densification (99%) and strongest mechanical properties; the compressive strength is 374 MPa. The structure of the ceramic matrix composite is homogeneous. Good adhesion between the inorganic and the organic component is observable using scanning electron microscopy.