Heat transfer simulation of the cure of thermoplastic particle interleaf carbon fibre epoxy prepregs

Thermochemical properties are needed to develop process models and define suitable cure cycles to convert thermosetting polymers into rigid glassy materials. Uncertainty surrounding the suitability of thermal analysis techniques and semi-empirical models developed for conventional composite materials has been raised for the new class of particle interleaf materials. This paper describes kinetics, conductivity, heat capacity and glass transition temperature measurements of HexPly® M21 particle interleaf material. Thermal models describing conventional, non-particle epoxy systems were fit to the data and validated through a thick-section cure. Results from curing experiments agree with heat transfer simulation predictions, indicating that established thermal analysis techniques and models can describe polymerisation and evolving material properties during processing of a material representing the class of interleaf toughened systems. A sensitivity study showed time savings up to about 20%, and associated energy-efficiency-productivity benefits can be achieved by using cure simulation for particle interleaf materials

Routine Million-Particle Simulations of Epoxy Curing with Dissipative Particle Dynamics

Mesoscale simulation techniques have helped to bridge the length scales and time scales needed to predict the microstructures of cured epoxies, but gaps in computational cost and experimental relevance have limited their impact. In this work, we develop an open-source plugin epoxpy for HOOMD-Blue that enables epoxy crosslinking simulations of millions of particles to be routinely performed on a single modern graphics card. We demonstrate the first implementation of custom temperature-time curing profiles with dissipative particle dynamics and show that reaction kinetics depend sensitively on the stochastic bonding rates. We provide guidelines for modeling first-order reaction dynamics in a classic epoxy/hardener/toughener system and show structural sensitivity to the temperature-time profile during cure. We conclude with a discussion of how these efficient large-scale simulations can be used to evaluate ensembles of epoxy processing protocols to quantify the sensitivity of microstructure on processing

Modelling the Pultrusion Process of Off Shore Wind Turbine Blades

This thesis is devoted to the numerical modelling of the pultrusion process for industrial products such as wind turbine blades and structural profiles. The main focus is on the thermo-chemical and mechanical analyses of the process in which the process induced tresses and shape distortions together with the thermal and cure developments are addressed. A detailed survey on pultrusion is presented including numerical and experimental studies available in the literature since the 1980s. Keeping the multi-physics and large amount of variables involved in the pultrusion process in mind, a satisfactory experimental analysis for the production requires considerable time which is obviously not a cost-efficient approach. Therefore, the development of suitable computational models is highly desired in order to analyse the process for different composite manufacturing aspects such as heat transfer, curing and solid mechanics

Managing heat phenomena in epoxy composites production via graphenic derivatives: synthesis, properties and industrial production simulation of graphene and graphene oxide containing composites

A commercial two-components epoxy resin formulation was successfully modified by adding graphene and related materials (GRMs) and the effect of these nanofillers was assessed on their thermomechanical properties as well as on the simulation of their industrial application for the production of thick composites objects with interesting results. GMRs were added in different concentrations in order to improve thermo-mechanical properties of the nano-composite thermoset. Different dispersion methods were taken into account in order to produce stable long-lasting dispersion of the GRMs, that can withstand a commercial shelf life. Addition of the GRMs improves the glass transition temperature of the nanocomposite up to 20 °C with respect to the plain commercial formulation, and both stress and elongation at break increase up to almost 4 times the original values. Moreover, the industrial curing of some of the more promising modified resins was computer-simulated when the two-components resins are used to produce a carbon-fibre reinforced thick composite beam. Simulation results show that some of the applied GRMs helps reducing or even completely preventing the overheat phenomena that are well renown to induce significant thermal stresses negatively affecting the final object performances. These interesting effects would contribute reducing the time required for a single industrial production cycle, since no time for overheat dispersion is required, thus helping increasing the production rate

Direct Resistive Heating Simulation Tool for the Repair of Aerospace Structures through Composite Patches

Bonded composite patches are very appropriate for aircraft structural repair, showing very good properties when compared with traditional mechanical fastening of metal sheets. The curing process of the composite patch must be done “onsite” and a direct resistive heating method has been proposed. The heat produced by the electric current through the Joule effect when crossing the patch carbon fibre bundles has been modelled with a Finite Element Program code, developed for the electric current equation. The heat conduction equation has also been modelled in the program, as well as the kinetics of the curing reaction of the composite resin. The electric resistivity of the materials is function of the temperature, so a nonlinear coupled system has been developed. Therefore, a complete simulation tool able to study different configurations, current intensities, materials, etc. for the composite patches is presented. A study case has been run with the developed code and results have been compared with experimental values. Good agreement is found.This work was developed under the European Seventh FrameworkProgram, Theme7Transport, Project IAPETUS [GrantAgreementno.ACP7-GA-2008-234333]