3-D textile reinforced composites for the transportation industry 55 Hand Lamination Pultrusion low tool costs -continuous relatively low fibre volume fraction Resin injection process very high manufacturing time only constant cross- (RTM) high manual work share sections high fibre volume fraction poor reproducibilit -curvature of profiles limited -relatively expensive toos relatively low tool costs high quality Impregnation cycle time >5 min. Techniques reproducible fibre volume fraction cycle time >5 min. -optimum combination with textile process high pressure for consolidation necessary expensive tools for complex components Thermoplastic Hybrid Yarn Technique 2.7 Impregnation techniques for textile structural composites. 210 bination of reinforcing fibres and thermoplastic 'matrix'fibres occurs at fibre level.In the co-weaving or co-braiding process the two fibre types are mixed during the textile process. The advantage of the first approach is that the textile processing of the reinforcing fibres can be improved because the tough thermoplastics protect the brittle glass or carbon fibres.Additionally,the composite L quality is better than co-weaving and co-braiding,owing to increased With a view to an overall cost evaluation,tooling may play an important role in low-and medium-volume manufacturing.In general,composite tools are much cheaper than steel tools.Therefore,part costs may be lower because of the use of composites for small series production,although mate- rial costs are much higher than those of steel. Nevertheless,the tooling technology for impregnating very complex textile preforms requires special developments to allow cost-effective com- ponent manufacturing.Promising techniques are,for example,the differ- ential pressure RTM or the so-called 'Scrimp process',where only one tooling half is hard and the other one is formed by a vacuum foil. Of special interest for complex hollow structures is the wax core tech- nique.These cores can be melted in very complex geometries and act,for example,as a braiding core during the textile process and as part of the impregnation tool during composite manufacturing.After curing they can be melted out completely.bination of reinforcing fibres and thermoplastic ‘matrix’ fibres occurs at fibre level. In the co-weaving or co-braiding process the two fibre types are mixed during the textile process. The advantage of the first approach is that the textile processing of the reinforcing fibres can be improved because the tough thermoplastics protect the brittle glass or carbon fibres. Additionally, the composite quality is better than co-weaving and co-braiding, owing to increased homogeneity. With a view to an overall cost evaluation, tooling may play an important role in low- and medium-volume manufacturing. In general, composite tools are much cheaper than steel tools. Therefore, part costs may be lower because of the use of composites for small series production, although mate￾rial costs are much higher than those of steel. Nevertheless, the tooling technology for impregnating very complex textile preforms requires special developments to allow cost-effective com￾ponent manufacturing. Promising techniques are, for example, the differ￾ential pressure RTM or the so-called ‘Scrimp process’, where only one tooling half is hard and the other one is formed by a vacuum foil. Of special interest for complex hollow structures is the wax core tech￾nique. These cores can be melted in very complex geometries and act, for example, as a braiding core during the textile process and as part of the impregnation tool during composite manufacturing. After curing they can be melted out completely. 3-D textile reinforced composites for the transportation industry 55 2.7 Impregnation techniques for textile structural composites. RIC2 7/10/99 7:25 PM Page 55 Copyrighted Material downloaded from Woodhead Publishing Online Delivered by http://woodhead.metapress.com Hong Kong Polytechnic University (714-57-975) Saturday, January 22, 2011 12:29:45 AM IP Address: 158.132.122.9