Abstract
Thermal conductivity data for dry carbon fibre fabrics are required for modelling heat transfer during composites manufacturing processes; however, very few published data are available. This article reports in-plane and through-thickness thermal conductivities measured as a function of fibre volume fraction ( Vf) for non-crimp and twill carbon reinforcement fabrics, three-dimensional weaves and reinforcement stacks assembled with one-sided carbon stitch. Composites made from these reinforcements and glass fibre fabrics are also measured. Clear trends are observed and the effects of Vf, de-bulking and vacuum are quantified along with orthotropy ratios. Limited differences between the conductivity of dry glass and carbon fibre fabrics in the through-thickness direction are reported. An unexpected trend in the relationship between that quantity and Vf is explained summarily through simple simulations.
Highlights
Carbon fibres offer excellent tensile properties and low densities leading to extensive use as reinforcements for composite materials
Knowledge of the thermal conductivity of dry reinforcements is paramount in assessing and modelling heat transfer during composites manufacturing processes such as resin film infusion (RFI) or semi-preg consolidation, as heat transfer rates through the dry reinforcements will impact the evolution of resin viscosity, consolidation and cure
Test series 1 probes the effects of textile architecture, de-bulking, vacuum and volume fraction (Vf) on the in-plane and through-thickness thermal conductivity of dry reinforcements, lrip and lrtt, for two reinforcements made of the same carbon fibres
Summary
Carbon fibres offer excellent tensile properties and low densities leading to extensive use as reinforcements for composite materials. Test series 1 probes the effects of textile architecture, de-bulking, vacuum and Vf on the in-plane and through-thickness thermal conductivity of dry reinforcements, lrip and lrtt, for two reinforcements made of the same carbon fibres. Test series 1 probed the effects of textile architecture, Vf, successive compaction and vacuum on lrip and lrtt for two reinforcements made from Toho Tenax HTS40 PAN-based carbon fibres. Test series 2 quantified the effects of textile architecture, reinforcement thickness and yarns made of different fibres extending along the thickness on lrip and lrtt measured on 3D woven reinforcement fabrics. Values of the total variability obtained in test series 3 were almost always below 1% for conductivities measured in the in-plane and through-thickness directions, for carbon stacks featuring one-sided stitching and those devoid of stitching, as well as for glass dry stacks and composites, with no notable outliers. A thermal conductivity lfip 1⁄4 lftt of 0.2 W mÀ1 KÀ1 was obtained from more than 20 in-plane and transverse measurements performed on single sheets and stacks of Dahlar® 50 mm thick
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