Effects of variation in autoclave pressure, temperature, and vacuum-application time on porosity and mechanical properties of a carbon fiber/epoxy composite

Abstract

This article presents results from investigation of the effects of variation in autoclave pressure, temperature, and vacuumapplication time on porosity, hot/wet (H/W) and room temperature/dry (RT/D) short beam shear (SBS) strength, and failure mechanism of a commercial carbon fiber/epoxy prepreg, Cycom IM7/977-2 unidirectional tape. Fourteen cure cycles were designed to study a wide range of curing pressures, curing temperatures, and two different vacuumapplication durations, including vacuum vented at recommended pressure and vacuum held throughout the cure cycle. The results showed that the SBS strength did not vary significantly over a relatively wide range of curing temperatures and pressures if vacuum was vented at recommended curing pressure; however, after a certain point, a decreasing trend in the SBS strength was observed by reducing the curing temperature and pressure. The C-scan images of panels cured with the vacuum held throughout the cure cycles revealed presence of a high-porosity crossshaped defect at the center of the panels. The observed defect became larger as the curing pressure decreased. The correlation between the SBS strength and the void content was studied using theoretical models and experimental data. The investigation of the failure modes for each panel showed a change in both the H/W and the RT/D failure mechanism as a result of variation in curing temperature and pressure.

A qualitative, process-parameter-based model for the release agent transfer during CFRP-part production: an approach to increase the initial bondability

“…autoclave process) are chosen to achieve a high interlaminar quality [13] or to reach a fast part production [14]. Unfortunately, the correlation of specific process parameters on the release agent transfer has not been investigated so far and is therefore subsequently discussed.…”

“…This is mainly done, to increase the interlaminar quality of the parts [13,26] (e.g. to reduce the amount of voids inside of the part [27]).…”

“…Nevertheless, even if the vapor pressure is reached during the production cycle, the volatile components of the release agent are mainly sucked outside of the laminate by the applied vacuum system within the experimental set-up (e.g. by the application of [24] vacuum bags [27,33]), proven by the reduction of voids after the application of an higher vacuum [13].…”

Influence of Curing Conditions on the Mechanical Properties of Silica-Phenolic Composites: A Comprehensive Study

“…Thus, several methods have been developed to establish optimum cure cycle to reach the desired structural performance [6][7][8][9][10][11]. Mechanical testing, is based on measurement of variations in a specific mechanical property by applying different cure regimes, is one of the most common and conventional methods used in the optimization of curing parameters [12][13][14][15].…”

“…Liu et al [21] revealed the changes in the tensile and interlaminar shear strengths of the carbon-epoxy laminates produced at different curing pressures. Despite this considerable effort devoted to assessing the relationship between curing parameters and mechanical properties of different types of thermoset matrix composites [12][13][14][15][16][17][18][19][20][21][22][23][24][25], there has yet to be any comprehensive study related the effect of curing processes on mechanical properties of silica phenolic composites. The aim of this study is to determine the effect of variations in the curing parameters on the mechanical properties of silica-phenolic composites.…”