Compression and permeability properties of multiaxial warp-knit preforms

Textile preform properties such as compression and permeability greatly influence the quality of the composite material and its performance, particularly those prepared by injection moulding techniques like resin transfer moulding (RTM). Directionally oriented warp-knit biaxial, triaxial and quadraxial glass fabrics have been studied for these preform properties. The preform compression properties were tested on the universal testing machine up to a maximum force of 250 N. The rate of test liquid flow through these preforms has been measured using the horizontalwicking test method. The permeability of these preforms has been analyzed based on the liquid flow-rate data. Fibre orientation and fibre volume fraction of the preforms are observed to be important factors influencing these preform properties

Multilayer interlocked woven fabrics: simulation of RTM mold filling operation with preform permeability properties

The simulation of resin flow during the resin transfer molding (RTM) process through multilayered textile fabric of known permeability and porosity has been attempted in this study. A simple three-dimensional computational fluid dynamics (CFD) simulation model has been developed and the results of the simulation are compared with the experimental RTM resin flow through multilayer interlocked woven structures. A multiphase simulation model is observed to reasonably predict the time for RTM mold filling. Fabric structural influence in terms of an Interlacement Index (I) has significant influence on the resin flow behaviour of the multilayered preform. A higher I of the preform means a longer time to fill the mold in both the experimental and simulated results. Images of the simulated flow front has been compared with the experimental results and it is observed that not only the mold filling time, but also the area of resin flow in the multilayer perform, is influenced by a fabric structural factor, I.(undefined

Influence of preform interlacement on the low velocity impact behavior of multilayer textile composites

Impact property of composite material is influenced not only by the type of fiber/matrix, but also by the woven structure of the reinforcement. Presence of 3D fibers in reinforcement is reported to enhance the performance of textile composites in an impact event. This article attempts to study the influence of interlacements in the multilayer woven interlocked 3D structures on the impact properties of the composite material reinforced with them. Low velocity impact testing was carried out on an instrumented drop weight impact tester to obtain loadelongation- time plots of the impact event. It has been observed that increased interlacement in the structure improves the impact resistance of the multilayer textile composites. Further, damage area maps have been developed to understand and analyze the interlacement effect on the impact behavior

Tribological properties of the directionally oriented warp knit GFRP composites

Recently, directionally oriented warp knit structures have gained prominence as reinforcements in composite materials due to their superior isotropic behaviour compared to other types of textile reinforcements. In the present study, composites prepared from four types of directionally oriented warp knit glass preforms with three different thermoset resins have been considered for the tribological characterisation. The tribological tests have been conducted on a reciprocating sliding test rig with ball-on-plate configuration. The tests were conducted in dry (unlubricated) and wet (aqueous) conditions at a fixed applied load (100 N) by varying the sliding distance. E-glass warp knitted preforms were used for the study including biaxial, biaxial non-woven, triaxial and quadraxial fabrics. The matrices were three different thermoset resins namely polyester, vinyl ester and epoxy resin. 13 14 15 16 17 18 19 The main aim of the study was to identify a composite having the best tribological performance, with regard to types of preform and matrix resin. Moreover, the results obtained from the tests have been used to develop a wastage map for these composites, as a function of sliding distance and type of preform in order to have a clear understanding of the tribological process.Fundação para a Ciência e a Tecnologia (FCT

Tribological behaviour of multilayered textile composites: the effect of reciprocating sliding frequency

Textile composites have been used for various applications because of their enhanced strength/weight ratio and versatile properties compared to other materials such asmetals. Many studies have investigated the tribological behaviour of textilecomposites, but none have focused onthe tribological characterization of 3D multilayeredwoven reinforced textile composites. Five types of 3-plywoven interlocked structures with varying interlacements were used as reinforcement for the nylon fibre/polyester resin composites for the present study. The influence of the textile structure interlacement on the tribological properties of the composite material (in terms ofwear volume)was investigated in thiswork. Further, special attention was given to understand the effect of sliding frequency on the tribological behaviour and driving wear mechanisms. The tests were conducted on a new class of reciprocating sliding wear tester, in dry (unlubricated) conditions, under a fixed applied load of 20N by varying the frequency of oscillating motion (0.5≤f≤8 Hz). In addition, testswere also conducted, at a constant frequency of 4Hz and as a function of several loads (5Nto 40 N). Fromthese tests, a 3-plywoven reinforced composite with the best tribological performance as a function of frequency and load was identified. It was observed that the type of woven structure had an influence on the tribological properties. Therefore, the selection of a textile composite should be based on the load and frequency at the service condition. The wear mechanisms involved in the tribological process were also analysedThe authors would like to express their gratitude for financial support provided by FCT, Portugal, through an individual project (SFRH/BPD/20344/2004), and an Asia Link program between the University of Minho, Portugal, and IIT Delhi, India, sponsored by the European Union. Thanks also to Mr. Sérgio Carvalho, who assisted with experimental work in the Tribology Lab at University of Minho