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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.15, #2)
Transverse Properties of Carbon Fibres by Nano-Indentation and Micro-mechanics by Romain Maurin; Peter Davies; Nicolas Baral; Christophe Baley (pp. 61-73).
In this study the transverse modulus of three high modulus (M40, M46 and K63712) carbon fibres has first been measured directly by nano-indentation measurements. Transverse tensile tests on unidirectional epoxy composites were then performed, and the comparison was made between transverse fibre properties from indentation and those needed to obtain the measured transverse composite modulus using micromechanics expressions. The latter tended to underestimate values from indentation, by up to 36%, and reasons for this are discussed. Values of transverse fibre modulus determined by both methods decrease as longitudinal fibre modulus increases.
Keywords: Carbon fibre; Epoxy; Nano-indentation; Transverse tensile
Windsurf-Board Sandwich Panels Under Static Indentation by C. Borsellino; L. Calabrese; G. Di Bella (pp. 75-86).
In recent years composite materials have found application in several fields as sport and sea transportation, where the incidence of the cost of materials is not significant compared with the required high mechanical performances. As a matter of fact, in some sports the whole equipment is nowadays realized in composite materials (i.e. windsurf boards, snowboards). The aim of the present work is to evaluate the mechanical performance of some sandwich structures produced by vacuum bagging technology for the windsurf boards production. The behaviour of the structures is tested under static indentation conditions; different fibres materials, for the skins, and different polystyrene foams, for the core, have been taken into account. In particular both the effect of the kind of fibre (glass, carbon and kevlar fibres) and the effect of the polystyrene cells size (and its density) have been investigated. The purpose was to obtain a stiff structure able to bear localized loads. Additionally, the effects induced on the indentation resistance by both the speed and the diameter of pin have been analysed.
Keywords: Sandwich; Expanded polystyrene; Indentation
Marine Composites Based on Low Styrene Content Resins. Influence of Lamination Procedure and Peel Plies on Interlaminar Resistance by Yves Perrot; Peter Davies; André Kerboul; Christophe Baley (pp. 87-97).
Delays between lamination of structures and secondary bonding are common in boatbuilding. This paper presents results from an experimental study of the influence of manufacturing procedure on the bond strength of unidirectional glass fibre reinforced polyester composites. Continuously laminated panels are taken as the reference and compared with panels overlaminated after delays of one week with and without peel ply protection. A standard polyester and low styrene DCPD formulation were tested. ILSS testing is shown not to be sensitive to the procedure but crack propagation tests show very large differences in mode I fracture energy. A small drop in fracture energy is measured for a delay of one week between lamination of the first and second halves of the specimen without peel ply. When a nylon peel ply is applied and removed just before overlamination of the second half very large drops in propagation energy, around 75%, are noted for both materials. Surface abrasion after peel ply removal enables fracture energy to be recovered for the standard polyester and to a lesser extent for the low styrene DCPD composite.
Keywords: Glass/polyester composites; Low styrene content resins; Lamination procedure; Peel ply; ILSS; Mode I
The Effects of Thermal Cycles on the Impact Fatigue Properties of Thermoplastic Matrix Composites by Tamer Sınmazçelik; Onur Çoban; Mustafa Özgür Bora; Volkan Günay; İsmail Cürgül (pp. 99-113).
The effects of thermal cycles on the impact fatigue properties of unidirectional carbon fibre reinforced polyetherimide (PEI) matrix composites were investigated. During the thermal cycles, samples were immersed into boiling water (100 °C) and subsequently to ice water (0 °C), 50, 200 and 500 times. The changes in viscoelastic properties of the composites were investigated by means of dynamic mechanical thermal analyzer (DMTA). At the second step, thermal cycled composites were subjected to repeated impact loadings, with different impact energies. Instrumented impact test results were presented as a function of force, energy, deformation during the experiments. The scanning electron microscope (SEM) studies were done in order to understand the morphology of fractured samples after impact fatigue loading. The number of thermal cycles and applied impact energy of the hammer are found to have a great importance on the fracture morphology of repeatedly impacted material, as expected.
Keywords: Polymer–matrix composites (PMCs); Thermal properties; Dynamic mechanical thermal analysis (DMTA); Scanning electron microscopy (SEM); Impact behaviour