TY - CHAP A1 - Stark, Wolfgang A1 - Bohmeyer, W. ED - Karbhari, V.M. T1 - Non-destructive evaluation (NDE) of composites: using ultrasound to monitor the curing of composites N2 - Typical composite materials for lightweight construction consist of a fibre (glass or carbon) reinforced thermosetting matrix. The impregnation of the fabric is made with liquid resin – usually epoxy resin or unsaturated polyester resin are used. The main processing methods are resin transfer moulding (RTM) and prepreg technology often used in combination with autoclave curing. After shaping, the resin must be cured. The final properties of the produced parts depend on the curing degree and the final glass transition temperature. Analytical methods and the use of ultrasound for online cure monitoring in the manufacturing process are introduced. Examples for the application of ultrasonic cure monitoring for the production of composite parts for traffic systems are also covered. KW - Epoxy KW - DSC KW - DMA KW - Kinetic KW - Autoclave KW - Curing KW - Glass transition KW - Curing behaviour KW - Curing degree KW - Rheology KW - Differential scanning calorimetry KW - Dynamic mechanical analysis KW - Sound velocity KW - Sound damping KW - Resin transfer moulding KW - RTM KW - Prepreg PY - 2013 SN - 978-0-85709-344-8 SN - 978-0-85709-355-4 U6 - https://doi.org/10.1533/9780857093554.1.136 SN - 2052-5281 SN - 2052-529X N1 - Serientitel: Woodhead publishing sereies in composites science and engineering – Series title: Woodhead publishing sereies in composites science and engineering VL - 43 IS - Part 1 / Chapter 7 SP - 136 EP - 181 PB - Woodhead Publishing Ltd CY - Cambridge, UK AN - OPUS4-28848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - McHugh, Jarlath A1 - Stark, Wolfgang T1 - Determination and interpretation of changes in thermophysical properties of a carbon-fibre prepreg during cure N2 - Epoxy composites used for high-end structural applications are typically cured under the influence of temperature and pressure causing a number of complex chemical and physical transformations. On heating a mould, temperature gradients will occur through the component which will depend largely on the thermophysical properties of the specific composite. The crosslinking reaction is exothermic leading to additional heat release, thus complicating heat transportation models. If such effects are not accounted for, it can lead to variations in resin flow, poor fibre wetting causing voiding and inhomogeneous cure, leading to shrinkage and unfavourable variations in moulded part geometry. Limited information is available for thermal models used in the manufacture of reinforced thermosets. Autoclave [1, 2] and laser or infra-red curing processes [3, 4] typically use constant values determined on fully cured parts. In this work, the variation in thermal conductivity (K) (W/(m K)), thermal diffusivity (a) (m(2)/s) and specific heat capacity at constant pressure (c(p)) (J/(g K) is determined for a carbon fibre prepreg during cure. It is the intention to improve understanding of how these parameters are related to chemical or physical transformations occurring during cure, and where estimates or shortcuts may be used for heat transfer models KW - Differential scanning calorimetry KW - Temerature KW - Epoxy system PY - 2016 U6 - https://doi.org/10.1016/j.polymertesting.2015.11.015 SN - 0142-9418 VL - 49 SP - 115 EP - 120 PB - Elsevier Science CY - Oxford AN - OPUS4-35788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -