TY - JOUR A1 - Stark, Wolfgang T1 - Investigation of the curing behaviour of carbon fibre epoxy prepreg by dynamic mechanical analysis DMA N2 - Carbon fibre prepregs have found widespread application in lightweight constructions. They are based on a carbon fibre fabric impregnated with reactive epoxy resin. Measurements were carried out using commercially available prepreg material. For Dynamic Mechanical Analysis (DMA), a single cantilever measuring device was applied. The DMA results were refined by additional DSC measurements. The measurements were carried out with dynamic heating in the temperature range -90 to 280 °C. The heating rates were 1 and 2 K/min, respectively. A glass transition of the uncured material (Tg0) near 1 °C, and crosslinking-induced vitrification and devitrification at the maximal glass transition temperature of the cured material (Tgmax) in the temperature range 220 to 230 °C were found. The activation energies for the glass transitions were determined using an Arrhenius plot. By detailed consideration of the influence of the frequency on the DMA data, indications for gelation were deduced. KW - CRP KW - Prepreg KW - Carbon fibre KW - Epoxy KW - DMA KW - DSC KW - Glass transition KW - Crosslinking KW - Vitrification KW - Devitrification PY - 2013 U6 - https://doi.org/10.1016/j.polymertesting.2012.11.004 SN - 0142-9418 VL - 32 IS - 2 SP - 231 EP - 239 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-27584 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stark, Wolfgang A1 - Jaunich, Matthias A1 - McHugh, J. T1 - Cure state detection for pre-cured carbon-fibre epoxy prepreg (CFC) using temperature-modulated differential scanning calorimetry (TMDSC) N2 - Carbon-fibre prepregs have found widespread use in lightweight applications. They are based on a carbon-fibre fabric impregnated with reactive epoxy resin. Prepreg materials are generally pre-cured so that they have a higher molecular weight than typical resins in order to reduce resin flow, which facilitates storage and later processing properties. The measurements were carried out using commercially available materials and follow the published DMA investigations of the same material. TMDSC was used to find the correlation between curing conditions, the degree of cure and glass transition temperature. TMDSC has the advantage over standard DSC that it enables better determination of the glass transition temperature, which is often accompanied by an exothermic curing reaction, and thus overshadowed. The influence of the amplitude of temperature modulation was tested in preliminary experiments. For non-cured material a glass transition temperature of approximately 0 °C was determined; whereas for the totally cured material it was approximately 230 °C. The changes in degree of cure, temperature of actual glass transition and post-reaction are given as a function of curing time at 180 °C. The correlation between actual glass transition temperature and degree of cure is derived. KW - Prepreg KW - Carbon fibre KW - Glass transition KW - Degree of curing KW - DSC KW - TMDSC PY - 2013 U6 - https://doi.org/10.1016/j.polymertesting.2013.07.007 SN - 0142-9418 VL - 32 IS - 7 SP - 1261 EP - 1272 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-29067 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -