Controlled composite processing based on off‐stoichiometric thiol‐epoxy dual‐curing systems with sequential heat release (SHR)

Abstract

Control of curing rate and exothermicity during processing of thermosetting composite materials is essential in order to minimize the formation of internal stresses leading to mechanical and dimensional defects in the samples, especially in thick composite samples. It was recently proposed that sequential heat release, an approach based on the kinetic control of the curing sequence of dual-curing thermosets, would enable a step-wise release of the reaction heat and therefore a better control of conversion and temperature profiles during the crosslinking stage. In this article, it is shown experimental proof of this concept obtained by means of an instrumented mold that can be used for the processing of small samples with and without carbon fiber reinforcement. Safe processing scenarios have been defined by numerical simulation using a simplified two-dimensional heat transfer model and validated experimentally.

Influence of variable‐stiffness layup configuration on curing deformation of curved‐surface structures

“…The curing deformation model, includes two Static General analysis steps, one is for the modeling of curing process, and the other is for the state after demolding. The following two jobs have been finished in this model: (1) Viscoelastic constitutive model of composite materials should be provided; (2) The curing deformation of composite structures should be calculated. To get the former job done, the subroutine UMAT is developed according to Formulas (5)-( 13).…”

“…Among the internal factors, geometric characteristics of structures and thermal properties of composite materials play an important role. Configurations about the mold and the curing cycle are the main external factors, 1 and they all have a great influence on the development of residual stress in composite structures.…”

In-Line Monitoring of a Curing Process With a Multisensor Concept

“…Since temperature measurement is also very important, three different temperature sensors, Pt1000, NTC10k and an I2C digital sensor, have been tested to suitability and are compared under the same measuring conditions. Both, in-line pressure and temperature information, provide improved monitoring of the curing process [8][9][10], thus serving as a basis for creating a digital twin using finite element (FE) simulation.…”