TY - THES

T1 - Influence of cure-induced shrinkage of pre-impregnated woven glass fiber fabrics on the temperature- and direction-dependent deformation of composites measured by digital image correlation

AU - Sagerer, Maike

N1 - embargoed until 31-08-2027

PY - 2022

Y1 - 2022

N2 - In the state-of-the-art printed circuit board (PCB) industry, one of the main PCB base materials which is used is epoxy resin in combination with woven glass fiber cloths. During processing, irreversible curing shrinkage occurs. The curing shrinkage of pure thermosets has already been sufficiently characterized, but measurements of thermoset/fiber composites are significantly more difficult and not possible using the standardized measurement set-ups. In previous experiments, a method combining measurements and finite element simulation for determining a shrinkage coefficient was determined, which is based on the curing of a strip of bi-material and measuring its deformation via digital image correlation. The aim of this thesis was now to characterize a whole family of materials comprising the same resin but different fiber fabrics in order to find a possible link between fiber fabric type, resin content and fabric count. comprising other resin types. To ensure this the measurement set-up had to be optimised because previous measurements showed significant variations between measurements. This optimisation included a temperature calibration of the measuring environment, which was determined batch- and position-dependent for all samples.By identifying correlations between those factors, it is then possible to make predictions about the deformation behavior of material families In addition, the curing behavior of the material family was determined with the help of model-free kinetics. By combining both approaches, a position- and temperature-dependent curing curve could be generated for each sample, which allows to compare the measured deformations of all samples in a normalised way. Furthermore, the evaluation of the measurement data showed an influence of the production process of the fiber fabrics, resulting in a direction-dependent deformation behavior even when measuring samples with symmetric fabric types.

AB - In the state-of-the-art printed circuit board (PCB) industry, one of the main PCB base materials which is used is epoxy resin in combination with woven glass fiber cloths. During processing, irreversible curing shrinkage occurs. The curing shrinkage of pure thermosets has already been sufficiently characterized, but measurements of thermoset/fiber composites are significantly more difficult and not possible using the standardized measurement set-ups. In previous experiments, a method combining measurements and finite element simulation for determining a shrinkage coefficient was determined, which is based on the curing of a strip of bi-material and measuring its deformation via digital image correlation. The aim of this thesis was now to characterize a whole family of materials comprising the same resin but different fiber fabrics in order to find a possible link between fiber fabric type, resin content and fabric count. comprising other resin types. To ensure this the measurement set-up had to be optimised because previous measurements showed significant variations between measurements. This optimisation included a temperature calibration of the measuring environment, which was determined batch- and position-dependent for all samples.By identifying correlations between those factors, it is then possible to make predictions about the deformation behavior of material families In addition, the curing behavior of the material family was determined with the help of model-free kinetics. By combining both approaches, a position- and temperature-dependent curing curve could be generated for each sample, which allows to compare the measured deformations of all samples in a normalised way. Furthermore, the evaluation of the measurement data showed an influence of the production process of the fiber fabrics, resulting in a direction-dependent deformation behavior even when measuring samples with symmetric fabric types.

KW - Aushärte Schrumpf

KW - Prepreg

KW - Verbundwerkstoff

KW - Duromer

KW - Matrix

KW - Messtechnik

KW - Glasfasergewebe

KW - Glasfasern

KW - Curing Shrinkage

KW - Prepreg

KW - PCB

KW - glasfiber

KW - shrinkage

KW - warp

KW - weft

M3 - Master's Thesis

ER -