246 3-D textile reinforcements in composite materials Table 8.2.Fibre properties of some typical natural and synthetic fibres Density Young's Tensile Strain failure (kg/m3×10) modulus failure (%) (NWm2×10) (N/m2×10) Natural organic polymer base Jute 1.46 10-25 400-800 1-2 Hemp 1.48 26-30 550-900 1-6 Flax 1.54 40-85 800-2000 3-2.4 Sisal 1.33 46 700 2-3 Coir 1.25 6 221 15-40 Cotton 1.51 1-12 400-900 3-10 Synthetic organic polymer base HT carbon (T300) 1.76 230 3530 1.5 HM carbon (M40) 1.83 392 2740 0.7 HM aramide 1.45 133 3500 2.7 Inorganic base E-glass 2.58 73 3450 4.8 S/R-glass 2.48 88 4590 5.4 ssaidmau'peaupoo/ 210 Note:Properties of natural materials are very variable,so the figures shown are averages and collected from a great variety of publications. 周 tance.Decreasing structural weight,often beneficial for performance improvement,not only reduces the quantity and cost of materials but also often reduces the production time,and consequently the cost of manufac- turing.A powerful approach to reach this goal is the matrix reinforcement with proper fibres,to high possible volume fractions,continuous and with a complete control of fibre orientations,in other words to control anisotropy.The success of composite applications,by volume and by number,can be ranked by the success of the applied manufacturing tech- niques (Fig.8.4).For all processes shown,suitable for short to continuous fibres,the introductory (pioneering)period was based on thermosetting polymers,from phenolics,polyesters,vinylesters to epoxies.In the case of injection moulding with short (<10mm)and pressing with longer fibre rein- forcements (<100mm),thermoset polymers are being increasingly replaced by more expensive but technically equivalent or better thermoplastics. However,the main reason for this is the cost reduction by cycle time reduc- tion.Most important among the technologies mentioned is injection mould- ing of generally small and complex parts.The reinforcement by fibres is limited with respect to length,volume percentage (<35%)and orientation control.Flow-moulding of larger thermoset and thermoplastic shell- structures (SMC and GMT)became important as well,especially for car
tance. Decreasing structural weight, often beneficial for performance improvement, not only reduces the quantity and cost of materials but also often reduces the production time, and consequently the cost of manufacturing. A powerful approach to reach this goal is the matrix reinforcement with proper fibres, to high possible volume fractions, continuous and with a complete control of fibre orientations, in other words to control anisotropy. The success of composite applications, by volume and by number, can be ranked by the success of the applied manufacturing techniques (Fig. 8.4). For all processes shown, suitable for short to continuous fibres, the introductory (pioneering) period was based on thermosetting polymers, from phenolics, polyesters, vinylesters to epoxies. In the case of injection moulding with short (<10 mm) and pressing with longer fibre reinforcements (<100 mm), thermoset polymers are being increasingly replaced by more expensive but technically equivalent or better thermoplastics. However, the main reason for this is the cost reduction by cycle time reduction. Most important among the technologies mentioned is injection moulding of generally small and complex parts. The reinforcement by fibres is limited with respect to length, volume percentage (<35%) and orientation control. Flow-moulding of larger thermoset and thermoplastic shellstructures (SMC and GMT) became important as well, especially for car 246 3-D textile reinforcements in composite materials Table 8.2. Fibre properties of some typical natural and synthetic fibres Density Young’s Tensile Strain failure (kg/m3 ¥ 103 ) modulus failure (%) (N/m2 ¥ 109 ) (N/m2 ¥ 106 ) Natural organic polymer base Jute 1.46 10–25 400–800 1–2 Hemp 1.48 26–30 550–900 1–6 Flax 1.54 40–85 800–2000 3–2.4 Sisal 1.33 46 700 2–3 Coir 1.25 6 221 15–40 Cotton 1.51 1–12 400–900 3–10 Synthetic organic polymer base HT carbon (T300) 1.76 230 3530 1.5 HM carbon (M40) 1.83 392 2740 0.7 HM aramide 1.45 133 3500 2.7 Inorganic base E-glass 2.58 73 3450 4.8 S/R-glass 2.48 88 4590 5.4 Note: Properties of natural materials are very variable, so the figures shown are averages and collected from a great variety of publications. RIC8 7/10/99 8:26 PM Page 246 Copyrighted Material downloaded from Woodhead Publishing Online Delivered by http://woodhead.metapress.com Hong Kong Polytechnic University (714-57-975) Saturday, January 22, 2011 12:31:28 AM IP Address: 158.132.122.9
3-D forming of continuous fibre reinforcements for composites 247 fibre content,orientation control fibre length versus manufacturing processes Vf Length process [%] [mm] thermo thermo sets plastics L injection crit <L<10 pressing 25% 0 moulding % injection moulding SRIM 10<L<100 RTM pressing BMC/SMC GMT 40% L∞ laminating 100 % tapelaying filament winding RTM pressing diaphragm forming 70% pultrusions 8.4 Industrial manufacturing techniques. parts.The length (<100mm)and volume percentage (<45%)of the rein- forcing fibres increase.The control of fibre orientations is similar to injec- tion moulding,limited to keeping fibres as random and uniformly distributed as possible.In the case of modern advanced structures (high loads,low weight),where controlled fibre placement is essential,designers and manufacturers still rely on techniques that are labour or capital inten- sive (laminating by hand or the use of dedicated equipment).In the case of some advanced composite applications,human labour is only replaced by cost reducing and accurate machines in the stage of pre-impregnation and the cutting of patches.Industrial laminating by tape or fabric laying machines is still limited to a few (aircraft)shell structures.The most suc- cessful techniques in terms of volume usage are the filament winding of
parts. The length (<100 mm) and volume percentage (<45%) of the reinforcing fibres increase. The control of fibre orientations is similar to injection moulding, limited to keeping fibres as random and uniformly distributed as possible. In the case of modern advanced structures (high loads, low weight), where controlled fibre placement is essential, designers and manufacturers still rely on techniques that are labour or capital intensive (laminating by hand or the use of dedicated equipment). In the case of some advanced composite applications, human labour is only replaced by cost reducing and accurate machines in the stage of pre-impregnation and the cutting of patches. Industrial laminating by tape or fabric laying machines is still limited to a few (aircraft) shell structures. The most successful techniques in terms of volume usage are the filament winding of 3-D forming of continuous fibre reinforcements for composites 247 8.4 Industrial manufacturing techniques. RIC8 7/10/99 8:26 PM Page 247 Copyrighted Material downloaded from Woodhead Publishing Online Delivered by http://woodhead.metapress.com Hong Kong Polytechnic University (714-57-975) Saturday, January 22, 2011 12:31:28 AM IP Address: 158.132.122.9
248 3-D textile reinforcements in composite materials pressure vessels and the pultrusion of composite profiles.Typical for the advanced composite sector is the use of continuous fibres(glass,aramid and carbon)and the high fibre volume percentages(<70%).It is still the domain of thermosetting polymers. Although the application of advanced continuous fibre reinforced com- posites may result in highly satisfactory structural performances [3],the volume and number of applications are still limited.The success of the advanced composites depends completely on the availability of fast and reproducible industrial manufacturing processes. A development of such an industrial process based on 3-D deformation, i.e.draping,of (impregnated)textile fabrics,is the subject of this chapter. The major deformation mechanisms,the geometrical draping-simulation strategies,finite element simulation and the final product optimization, essential for designers and analysts,is outlined in the following sections. The draping process is part of a press-forming cycle,more specifically the press forming of textile fabrics which are impregnated to a certain extent with thermosetting or preferably thermoplastic polymers.Nowadays many industrial impregnation strategies for both thermosetting or thermoplastic 业 polymers are available.Once the fabric has been impregnated and the polymer brought to a deformable state,e.g.by heating,the plain sheet can be formed into a shell structure in seconds by press forming and(re)con- solidation in the last phase by application of matching dies.This technol- ogy can be used to produce high-quality preforms for the (thermosetting) resin injection or transfer moulding (RTM)of advanced aircraft and car components (Fig.8.4).Major successes are,however,achieved in the press 人兰今 份 forming of continuous reinforced thermoplastic composite parts (Figs.8.5 and 8.6).Similar to the already-mentioned technologies for advanced com- posites,high fibre volume contents and reproducible fibre orientations are typical for press forming.The speed is comparable with the ordinary injec- tion moulding and flow-moulding of short fibre reinforced parts.The pres- sure levels are relatively low:for forming,1 bar or less;for (re-) consolidation,10-40 bar.When the heating and cooling times are consid- ered as well (for thin-walled structures,a matter of seconds),it is clear that the press forming of advanced composites is not only attractive because of its manufacturing speed,but also because of the light-weight equipment and minimum energy required [4]. 8.1.4 Outline of the simulation and optimization strategy The following sections deal with the simulation and optimization of 3-D formed continuous fibre reinforced components.In the scheme shown in Fig.8.5 the role they play in an integral process of design and analysis is clarified.When automated structural optimization is applied,the scheme
pressure vessels and the pultrusion of composite profiles. Typical for the advanced composite sector is the use of continuous fibres (glass, aramid and carbon) and the high fibre volume percentages (<70%). It is still the domain of thermosetting polymers. Although the application of advanced continuous fibre reinforced composites may result in highly satisfactory structural performances [3], the volume and number of applications are still limited. The success of the advanced composites depends completely on the availability of fast and reproducible industrial manufacturing processes. A development of such an industrial process based on 3-D deformation, i.e. draping, of (impregnated) textile fabrics, is the subject of this chapter. The major deformation mechanisms, the geometrical draping–simulation strategies, finite element simulation and the final product optimization, essential for designers and analysts, is outlined in the following sections. The draping process is part of a press-forming cycle, more specifically the press forming of textile fabrics which are impregnated to a certain extent with thermosetting or preferably thermoplastic polymers. Nowadays many industrial impregnation strategies for both thermosetting or thermoplastic polymers are available. Once the fabric has been impregnated and the polymer brought to a deformable state, e.g. by heating, the plain sheet can be formed into a shell structure in seconds by press forming and (re)consolidation in the last phase by application of matching dies. This technology can be used to produce high-quality preforms for the (thermosetting) resin injection or transfer moulding (RTM) of advanced aircraft and car components (Fig. 8.4). Major successes are, however, achieved in the press forming of continuous reinforced thermoplastic composite parts (Figs. 8.5 and 8.6). Similar to the already-mentioned technologies for advanced composites, high fibre volume contents and reproducible fibre orientations are typical for press forming. The speed is comparable with the ordinary injection moulding and flow-moulding of short fibre reinforced parts. The pressure levels are relatively low: for forming, 1 bar or less; for (re-) consolidation, 10–40 bar. When the heating and cooling times are considered as well (for thin-walled structures, a matter of seconds), it is clear that the press forming of advanced composites is not only attractive because of its manufacturing speed, but also because of the light-weight equipment and minimum energy required [4]. 8.1.4 Outline of the simulation and optimization strategy The following sections deal with the simulation and optimization of 3-D formed continuous fibre reinforced components. In the scheme shown in Fig. 8.5 the role they play in an integral process of design and analysis is clarified. When automated structural optimization is applied, the scheme 248 3-D textile reinforcements in composite materials RIC8 7/10/99 8:26 PM Page 248 Copyrighted Material downloaded from Woodhead Publishing Online Delivered by http://woodhead.metapress.com Hong Kong Polytechnic University (714-57-975) Saturday, January 22, 2011 12:31:28 AM IP Address: 158.132.122.9
3-D forming of continuous fibre reinforcements for composites 249 Resin Transfer Moulding Rapid Press Forming (Thermosets) (Thermoplastics) Fabric Parameters Product Design(CAD) Fabric Deformation DRAPE Fibre Placement woo'ssaidmau//:dny Aq Checks on: RTM Simulation 6'ZZIEI'85I :ssauppV dl Drapeability Stiffness /Strength (FEM Analysis) Tool Design Modifications Modifications Predictable Reproducible Fibre Placement Preform Product 8.5 Design of advanced composite shell structures
3-D forming of continuous fibre reinforcements for composites 249 8.5 Design of advanced composite shell structures. RIC8 7/10/99 8:26 PM Page 249 Copyrighted Material downloaded from Woodhead Publishing Online Delivered by http://woodhead.metapress.com Hong Kong Polytechnic University (714-57-975) Saturday, January 22, 2011 12:31:28 AM IP Address: 158.132.122.9
250 3-D textile reinforcements in composite materials a WV8Z:IE:ZI I IOZ 'ZZ Anur 'Aupines b) 8.6 Typical continuous fibre reinforced products,manufactured using a thermoforming process:(a)automotive chassis part;(b)bicycle wheel. will alter somewhat,as the entire process must be controlled by the applied optimizer (see Fig.8.19). A general description of thermoforming of continuous fibre reinforced thermoplastic(CFRTP)products is given in Section 8.2.Numerical simu- lation of the forming process is the topic of Section 8.3.In this section,the discussion is mainly restricted to geometrical approaches.This choice has
will alter somewhat, as the entire process must be controlled by the applied optimizer (see Fig. 8.19). A general description of thermoforming of continuous fibre reinforced thermoplastic (CFRTP) products is given in Section 8.2. Numerical simulation of the forming process is the topic of Section 8.3. In this section, the discussion is mainly restricted to geometrical approaches. This choice has 250 3-D textile reinforcements in composite materials 8.6 Typical continuous fibre reinforced products, manufactured using a thermoforming process: (a) automotive chassis part; (b) bicycle wheel. RIC8 7/10/99 8:26 PM Page 250 Copyrighted Material downloaded from Woodhead Publishing Online Delivered by http://woodhead.metapress.com Hong Kong Polytechnic University (714-57-975) Saturday, January 22, 2011 12:31:28 AM IP Address: 158.132.122.9