Fibres epoxy composites containing

Shih studied the thermal behavior of an epoxy resin reinforced with water bamboo husks fibres and powders [42]. The char yield increased from 8.9 % for the epoxy resin to 10.1-13.6 % for the composites containing 10 % bamboo fibres or powder. The results showed that the addition of bamboo powder or fibres to epoxy systems would raise the char yield of the sample, therefore could improve the flame retardancy of these materials. Similar results were obtained in the case of Phormium tenax fibres reinforced epoxy composites, containing 20 % fibres. The presence of plant fibres determined an increase of the composites thermal stability, due to the improved fibre-matrix interactions [43]. 

Strength calculations on angle-ply laminates are based upon the elastic analysis described in 8.4.2. The strains produced in the laminate by a given set of applied stresses are first calculated, using the computed laminate stiffness constants. Stresses corresponding to these strains are then calculated for each layer of the laminate. These stresses are then expressed in terms of stresses parallel to and normal to the fibres, and the combination of stresses is compared with strength criteria for unidirectional material, which should preferably be obtained by experiment. Results for a three-direction carbon fibre-epoxy composite (0, 0) under tensile stress in the 0 = O direction are shown in Fig. 8.23. The composite contains 60 vol % fibre R is the fraction of plies which are angled at 0 and 1 — R is the fraction at W = 0. 

Epoxy composites containing fibres and a nanostructured filler... 

Figure 9.9 Dependence of iLSS of epoxy resin composites containing 60% % fibers on piasma poiymer deposition time. Source Reprinted with permission from Weisweiier W, Schiitter K, Surface modification of carbon fibres by piasma poiymerization, Figueiredo JL, Bernardo CA, Baker RTK, Huttinger KJ eds., Carbon Fibers Filaments and Composites, Kiuwer Academic, Dordrecht,...

Composites containing 60 vol. % carbon fibres in an epoxy resin of type LY556 cured with diamin HT972 (both firom Ciba Geigy Comp.) were manufactured to investigate adhesion between fibres and resin. 

To investigate the adhesion between fibres and matrix, composites containing 60 vol. % of coated Hercules AS4 and Grafil XAS carbon fibres in a matrix of epoxy resin were manufactured. 

Figure 6.8 The flexural stress versus strain curves for glass fibre-reinforced CTPEGA-modified epoxy-based composites (containing 0-40 phr of CTPEGA) Reprinted with permission from D. Ratna, T.K. Chongdar and B.C. Ghakrahorty, Polymer Composites, 2004,25,165. 2004, John Wiley and Sons Publishers...

Electrical conductivity measurements have been reported on a wide range of polymers including carbon nanofibre reinforced HOPE [52], carbon black filled LDPE-ethylene methyl acrylate composites [28], carbon black filled HDPE [53], carbon black reinforced PP [27], talc filled PP [54], copper particle modified epoxy resins [55], epoxy and epoxy-haematite nanorod composites [56], polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) blends [57], polyacrylonitrile based carbon fibre/PC composites [58], PC/MnCli composite films [59], titanocene polyester derivatives of terephthalic acid [60], lithium trifluoromethane sulfonamide doped PS-block-polyethylene oxide (PEO) copolymers [61], boron containing PVA derived ceramic organic semiconductors [62], sodium lanthanum tetrafluoride complexed with PEO [63], PC, acrylonitrile butadiene [64], blends of polyethylene dioxythiophene/ polystyrene sulfonate, PVC and PEO [65], EVA copolymer/carbon fibre conductive composites [66], carbon nanofibre modified thermotropic liquid crystalline polymers [67], PPY [68], PPY/PP/montmorillonite composites [69], carbon fibre reinforced PDMS-PPY composites [29], PANI [70], epoxy resin/PANI dodecylbenzene sulfonic acid blends [71], PANI/PA 6,6 composites [72], carbon fibre EVA composites [66], HDPE carbon fibre nanocomposites [52] and PPS [73]. 

Electrical resistance measurements have been reported on PANI/cerium oxide composites [48], polyester fibres and carbon containing epoxy composites [74]. 

Epoxy systems used in structural applications, whether as adhesives or the matrix of fibre-reinforced composites, are normally cured under some pressure and can be regarded as in closed containers. Studies on the kinetics and mechanisms of cure chemistry are often conducted without pressure in containers essentially open to the atmosphere. Extensive thermal analysis examinations at this Laboratory on a range of epoxy formulations have shown that for such fundamental quantities as the heat of reaction substantially different values can be obtained by using open or hermetic pans (Table 2). These differences are apparent with both the TDI-DMA adduct and dicyandiamide as curing agent but not with DDS. 

Resin transfer moulding (RTM) is a low-pressure variation of transfer moulding where, instead of granules or preforms, a pre-mixed resin and catalyst (hardener) is injected into a closed mould containing dry glass, carbon or aramid fibre reinforcement. When the resin has cooled, the mould is opened and the composite part ejected. The resins used include polyester, vinylester, epoxies, phenolics and methyl methacrylate combined with pigments and fillers. Applications include small complex aircraft and automotive components as well as automotive body parts, baths and containers. 

Figure 6.1 Schematic comparison of a macrocomposite containing 1 pmx25 pm fibres in an amorphous matrix to that of a nanocomposite at the same volume fraction of filler, but containing 1 nmx25 nm fibres. Constituents in any composite the matrix (white), the reinforcement (fibre, red) and the so-called interfacial region (green). Scanning electron micrograph shows E-glass reinforced polyolefin (15 mm) and transmission electron micrograph shows montmorillanite-epoxy nanocomposite (1 nm thick layers)." ...

Pultrusion is a simple technique which is employed mostly for fabrication of products based on unsaturated polyester resins (or other resins like epoxy, vinyl ester) and continuous strand mats (fibre or fabric). A pultrusion machine consists of creel for supplying fibre, a resin tank, forming dies, machined dies with a temperature control facility, a puller and a saw for cutting the product from a continuous composite product. The continuous strand mats are passed through a bath containing a mixture of resin and curatives. In the resin bath, the fibre is passed through a series of rods to remove entrapped air and excess resin to ensure complete wetting of the fibre. 

Specimens used for compressive strength measurements were prepared by a modified pultrusion process. Bundles containing carbon and HP-PE yarns in known proportions were immersed in a bath of epoxy resin and pulled into tubes with PTFE-inserts (6 mm internal diameter). Carbon and HP-PE yarns were intermingled as homogeneous as possible. The samples were cured for 4 hours at 80 C and then post-cured at 110 C for 12 hours. After curing specimens were removed from the mold and cut into 12 mm lengths using a low speed diamond saw. Volume fraction of fibres was held constant at 50% and the proportions of HP-PE fibre in the composite was varied from 0 to 100% with steps of 20%. 

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