Effect of transcrystallization in carbon fiber reinforced poly(p-phenylene sulfide) composites on the interfacial shear strength investigated with the single fiber pull-out test

Non-Isothermal Crystallization Kinetics and Activation Energy for Crystal Growth of Polyamide 66/Short Glass Fiber/Carbon Black Composites

This study presents the effect of the addition of 0.4 wt.% carbon black (CB) to polyamide 66 (PA66) containing 30 wt.% short glass fibers (GFs) on the behavior of composite thermal crystallization. Composites were studied by differential scanning calorimetry analysis (DSC) at different cooling rates using wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM). This thermal crystallization study highlights the nucleation effect of GFs that promote PA66 crystallization by significantly increasing crystallization kinetics and rates. The activation energies (Eas) calculated by model-free (FWO; KAS) and model-fitting (Kissinger method and C-R method) approaches showed that the combination of both GF and CB decreases the activation energy with respect to neat PA66, meaning that the presence of both additives facilitates crystallization. The Coats-Redfern and Criado methods showed that the crystallization of neat PA66 and related composites follows the second-order reaction, i.e., the decelerated reaction, evidencing compatibility between GFs and the matrix.

Imidazolium Salt for Enhanced Interfacial Shear Strength in Polyphenylene Sulfide/Ex-PAN Carbon Fiber Composites

Processing structural or semi-structural thermoplastic-based composites is a promising solution to solve the environmental issues of the aeronautic industry. However, these composites must withstand high standard specification to ensure safety during transportation. For this reason, there is a real need to develop strong interactions between thermoplastic polymers and reinforcement fibers. This paper investigates relationships between the surface chemistry, microstructure and micromechanical properties between polyphenylene sulfide and ex-PAN carbon fibers. The incorporation of ionic salt such as 1,3-Bis(4-carboxyphenyl)imidazolium chloride into neat polyphenylene sulfide was able to significantly increase the interfacial shear strength measured by microbond micromechanical test combined with different carbon fiber surfaces treatment.

Strain Rate Dependence of Compressive Mechanical Properties of Polyamide and Its Composite Fabricated Using Selective Laser Sintering under Saturated-Water Conditions

In this work, polyamide 12 (PA12) and carbon fiber reinforced polyamide 12 (CF/PA12) composites were fabricated using selective laser sintering (SLS), and the coupling effects of the strain rate and hygroscopicity on the compressive mechanical properties were investigated. The results showed that the CF/PA12 had a shorter saturation time and lower saturated water absorption under the same conditions, indicating that the SLS of CF/PA12 had lower hydrophilia and higher water resistance when compared to the SLS of PA12. It was observed that as the strain rate increased, and the ultimate compression strength and the yield strength monotonically increased with almost the same slope, indicating that the strain rate had the same positive correlation with the compressive strength of the SLS of PA12 and CF/PA12. The water immersion results showed a significant reduction of 15% in the yield strength of SLS of PA12, but not very significant in CF/PA12. This indicated that the carbon fiber was favorable for maintaining the mechanical properties of polyamide 12 after absorbing water. The findings in this work provide a basic knowledge of the mechanical properties of SLS polyamide under different loading and saturated-water conditions and thus is helpful to widen the application of SLS products in harsh environments.

Tailored Interfaces in Fiber-Reinforced Elastomers: A Surface Treatment Study on Optimized Load Coupling via the Modified Fiber Bundle Debond Technique

The interface between the reinforcement and surrounding matrix in a fibrous composite is decisive and critical for maintaining component performance, durability, and mechanical structure properties for load coupling assessment, especially for highly flexible composite materials. The clear trend towards tailored solutions reveals that an in-depth knowledge on surface treating methods to enhance the fiber–matrix interfacial interaction and adhesion properties for an optimized load transfer needs to be ensured. This research aims to quantify the effect of several surface treatments for glass fibers applied in endless fiber-reinforced elastomers with pronounced high deformations. Due to this, the glass fiber surface is directly modified with selected sizings, using a wet chemical treatment, and characterized according to chemical and mechanical aspects. For this purpose, the interfacial adhesion performance between fibers and the surrounding matrix material is investigated by a modified fiber pull-out device. The results clearly show that an optimized surface treatment improves the interface strength and chemical bonding significantly. The fiber pull-out test confirms that an optimized fiber–matrix interface can be enhanced up to 85% compared to standard surface modifications, which distinctly provides the basis of enhanced performances on the component level. These findings were validated by chemical analysis methods and corresponding optical damage analysis.

Comparison and Impact of Different Fiber Debond Techniques on Fiber Reinforced Flexible Composites

The focus of this paper is the realization and verification of a modified fiber bundle pull-out test setup to estimate the adhesion properties between threads and elastic matrix materials with a more realistic failure mode than single fiber debond techniques. This testing device including a modified specimen holder provides the basis for an adequate estimation of the interlaminar adhesion of fiber bundles including the opportunity of a faster, easier, and more economic handling compared to single fiber tests. The verification was done with the single-fiber and microbond test. Overall, the modified test setup showed the typical pull-out behavior, and the relative comparability between different test scales is given.