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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.14, #4)
A Meso–Macro Three Node Finite Element for Draping of Textile Composite Preforms by Nahiène Hamila; Philippe Boisse (pp. 235-250).
The composite textile reinforcement draping simulations allows the conditions for a successful process to be determined and, most importantly, the positions of the fibres after forming to be known. This last point is essential for the structural computations of the composite part and for resin injection analyses in the case of LCM processes. Because the textile composite reinforcements are multiscale materials, continuous (macro) approaches and discrete (meso) approaches that model the yarns have been developed. The finite element that is proposed in this paper for textile fabric forming is composed of woven unit cells. The mechanical behaviour of these is analyzed by 3D computations at the mesoscale regarding biaxial tensions and in plane shear. The warp and weft directions of the woven fabric can be in arbitrary direction with respect to the direction of the element side. This is very important in the case of multi-ply deep drawing and when using remeshing. The element is efficient because it is close to the physic of the woven cell while avoiding the very large number of unknowns in the discrete approach. A set of validation tests and forming simulations on single ply and multi-ply are presented and show the efficiency of the approach. In particular the importance of the in-plane shear behaviour is emphasized in the case of a draping on a cube.
Keywords: Fabrics/textiles; Finite element analysis; Forming; Preform; Meso–macro
Fire Retardancy of Natural Fibre Reinforced Sheet Moulding Compound by T. D. Hapuarachchi; G. Ren; M. Fan; P. J. Hogg; T. Peijs (pp. 251-264).
Due to environmental awareness and economical considerations, natural fibre reinforced polymer composites seem to present a viable alternative to synthetic fibre reinforced polymer composites such as glass fibres. This is a feasibility study to asses the potential application of natural fibre reinforced sheet moulding compound materials (NF-SMC) for the use in building applications, with particular emphases to their reaction to fire. The reinforcing fibres in this study were industrial hemp fibres. The cone calorimeter which asses the fire hazard of materials by Heat Release Rate (HRR) was used, radiant heat fluxes of 25 and 50 kW/m2 were utilised to simulate an ignition source and fully developed room fire conditions respectively. The results acquired here demonstrate that the NF-SMC can compete with current building materials in terms of their fire behaviour. The peak heat release value for the fire retardant (FR) NF-SMC was 176 kW/m2 conversely for a non-FR NF-SMC was 361 kW/m2.
Keywords: Natural fibre; Polymer composites; Cone calorimetery; Fire retardancy; Sheet moulding compound
Buckling Characteristics of Symmetrically and Antisymmetrically Laminated Composite Plates with Central Cutout by Buket Okutan Baba; Aysun Baltaci (pp. 265-276).
A numerical and experimental study was carried out to determine the effects of anti-symmetric laminate configuration, cutout and length/thickness ratio on the buckling behavior of E/glass-epoxy composite plates. The buckling loads were presented for symmetrically and anti-symmetrically laminated plates subjected to axial compression load. The study included two different laminate configurations ([90/45/−45/0]as and [90/45/−45/0]s), two different cutout shapes (circular and semi-circular), two different length/thickness ratios (L/t = 75 and 37.5) and three boundary conditions (clamped–clamped [CC], clamped–pinned [CP] and pinned–pinned [PP]). Firstly, the buckling loads of eight-ply E/glass-epoxy rectangular plates were determined experimentally. Then, the buckling loads of the laminated composites were calculated by ANSYS finite-element computer code. The changing in buckling load of the composites due to the presence of cutout and changing of length/thickness ratio was calculated. Finally, the experimental test results were compared to the buckling loads of plates obtained from the finite element analysis.
Keywords: Laminated composites; Cutout; Buckling; Finite element analysis; Stacking sequence
Preparation and Mechanical Properties of Carbon Fiber Reinforced (BC x –SiC) n Multilayered Matrix Composites by Wenbin Yang; Litong Zhang; Yongsheng Liu; Laifei Cheng; Weihua Zhang (pp. 277-286).
A boron doped carbon materials (BC x ) was prepared by chemical vapor deposition and a 3D (BC x –SiC) n multilayered matrix composite reinforced by carbon fiber, C/(BC x –SiC) n , was prepared by chemical vapor infiltration (CVI). XPS and SEM results showed that the BC x matrix had a boron content of 15 at.% and exhibited a very finely laminated structure. XRD analysis showed the BC x matrix was mainly carbon with B4C crystals in it. SEM and EDS results showed that the BC x layers and the SiC layers were deposited within the interspaces of fiber bundles, alternately arranged and paralleled to each other as designed. The fracture energy of the composite was about 16.8 KJ m−2. Flexural strength–displacement curve showed a remarkable metal-like yielding stage. Multiple fracture microstructures were induced by the multilayered matrix, such as delaminations of the multilayered matrix, deflections and propagations of cracks spread in the multilayered matrix layer by layer and long pullout of fiber bundles together with fiber clusters with multi-step pull-out structures. It was suggested that these special fracture behaviors absorbed a great deal of energy during the stress increasing and released the stress concentration, in this way, the toughness of the materials was improved.
Keywords: Multilayered matrix composite; Boron doped carbon; Microstructure; Mechanical properties