Special Issue "Fibre-Reinforced Composites"

Guest Editor
Prof. Dr. Volker Altstädt
Department of Polymer Engineering, University of Bayreuth, D-95447 Bayreuth, Germany
Website: http://www.bimf.uni-bayreuth.de/en/team/Altstaedt/index.html
E-Mail:
Phone: +49 921 557470
Fax: +49 921 557473

Dear Colleagues,

The light weight design potential of fibre reinforced polymer composites leads to increasing applications of these materials in various industrial sectors such as aerospace or automotive industry. Moreover, nowadays we observe the replacement of a number of conventional engineering materials thanks to the superior mass-specific mechanical performance and good processability of fibre reinforced polymers.

This potential can be further explored by combining the right components and the right processing techniques. This offers the possibility of tailoring the fibre reinforced composites performance in a very wide range, according to the respective requirements.

In this special issue the latest developments in the field of fibre reinforced polymeric composites are discussed. High performance continuous carbon-fibre reinforced thermosetting polymers as well as the mass produced and widespread short glass-fibre reinforced thermoplastics are here included. New material combinations like natural fibre reinforced polymers or continuous fibre reinforced thermoplastics are of increasing scientific interest. Furthermore novel trends related to the single components, like fibre and resin modification or textile processing techniques, e. g. performing, are covered.

But how do the processing, the single components and their interaction affect the final material`s properties? This special issue is based on the fundamental understanding of the processing-structure-properties-relationships in the field of fibre-reinforced polymers.

Prof. Dr. Volker Altstädt
Guest Editor

Submission

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• polymer matrix composites
• preforming
• processing
• mechanical properties
• fracture mechanics
• fatigue
• polymer
• morphology
• fibre length
• interphase

Type of Paper: Article
Title: Toughening of a Carbon-Fibre Composite Using Electrospun Poly(hydroxyether of bisphenol A) Nanofibrous Membranes through Inverse Phase Separation and Inter-Domain Etherification
Author: Kevin Magniez et al.
Affiliation: Institute for Technology Research and Innovation, Deakin University, Victoria, Waurn Ponds 3217, Australia; E-Mail: kevin.magniez@deakin.edu.au
Abstract: The interlaminar toughening of a carbon fibre reinforced composite by interleaving a thin layer (~20 microns) of poly(hydroxyether of bisphenol A) (phenoxy) nanofibres was explored in this work. Nanofibres free of defect and averaging several hundred nanometres were produced by electrospinning directly onto a pre-impregnated carbon fibre material (Toray G83C) at various concentrations between 0.5 wt.% and 2 wt.%. During curing at 150 ºC, phenoxy diffuses through the epoxy resin to form a semi interpenetrating network with an inverse phase type of morphology where the epoxy became the co-continuous phase with a nodular morphology. This type of morphology improved the fracture toughness in mode I (opening failure) and mode II (in-plane shear failure) by up to 150% and 30%, respectively. Interlaminar shear stress test results showed that the interleaving did not negatively affect the effective in-plane strength of the composites. Furthermore, there was some evidence from DMTA and FT-IR analysis to suggest that inter-domain etherification between the residual epoxide groups with the pendant hydroxyl groups of the phenoxy occurred, also leading to an increase in glass transition temperature (~ 7.5 °C).

Type of Paper: Article
Title: Novel Repair Concept for Composite Materials by Repetitive Geometrical Interlock Elements
Authors: Werner Hufenbach ¹, Frank Adam ¹, Thomas Heber ^1,*, Nico Weckend ¹, Friedrich-Wilhelm Bach ², Thomas Hassel ² and David Zaremba ²
Affiliation: ¹ Technische Universität Dresden, Institut für Leichtbau und Kunststofftechnik, Holbeinstr. 3, 01307 Dresden, Germany; E-Mail: t.heber@ilk.mw.tu-dresden.de
² Leibniz Universität Hannover, Institut für Werkstoffkunde, An der Universität 2, 30823 Garbsen, Germany
Abstract: Material adapted repair technologies for fibre-reinforced polymers with thermosetting matrix systems are currently characterized by high efforts for repair preparation and accomplishment in all industrial areas of application. In order to allow for a consistent distribution of material and geometrical parameters over the repair zone, a novel composite interlock repair concept is introduced, which is based on a repair zone with undercuts prepared by water-jet technology. The presented numerical and experimental sensitivity analyses make a contribution to the systematic development of the interlock repair technology with respect to material and geometrical factors of influence. The results show the ability of the novel concept for a reproducible and automatable composite repair.
Keywords: composite repair; fibre-reinforced polymers; positive locking connection

Title: Control of the Fiber Aspect Ratio in Natural Fiber Thermoplastic Composites
Author: Ahmed El Sabbagh et al.
Affiliation: Institute of Polymer Materials and Plastics Engineering, Clausthal University of Technology, Clausthal-Zellerfeld, Germany; E-Mail: ahmed.sabbagh@tu-clausthal.de
Abstract: Natural fibre thermoplastic composites are already commercialized. Therefore, increasing the added value of such composites through the good selection of the process parameters of the available compounding systems is mandatory. This article deals with the effect of the manufacturing process on the fiber aspect ratio and in turn the mechanical properties of natural fiber thermoplastic composites. The recommended aspect ratio is dependant on fibre to matrix stiffness but approximately an aspect ratio of 20 or more ensures efficient load transfer. Twin screw extruder and mixing kneader are common compounders for continuous and batch production respectively. Technical flax fibers and Polypropylene are compounded together using an extruder and a kneader. The investigated parameters in the case of using the twin screw extruder are: 
- The extruder screw layout where four layouts are tried. One is characterized with massive kneading. The second has low fewer kneading blocks. Third one has teeth block which cuts the fibers during feeding and the fourth has multi processing elements MPE developed for help feeding of moist natural fibers. 
- The fiber content of 10, 20 and 30 wt%.
- The shear rate applied by compounding which are 100, 200 and 300 rpm. 
The resulting fiber dimensions are compared to those of the kneading experiment after long mixing time. Fiber length, diameter and hence the aspect ratio are measured microscopically. The dimensions are found to follow a weibull distribution. Finding out the weibull distribution parameters facilitate the strength and stiffness models deal with the fibre distributions. Finally the effect of the aspect ratio change is correlated with the mechanical properties of the produced composites. Low shear rate was found to be optimum for the composite filled with 10 wt% fibers. Higher shear rate is suitable for higher fiber content. Screw of massive kneading power has a negative effect on the composite filed with 30 wt% fiber.