Rapidly cured out-of-autoclave laminates: Understanding and controlling the effect of voids on laminate fracture toughness

Agius, Steven; Fox, Bronwyn

doi:10.1016/j.compositesa.2015.02.023

Cited by 17 publications

(16 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These voids are mostly observed in the resin-rich regions of the material. The presence of large voids is expected to be detrimental to the mechanical properties due to their deleterious effects on the crack propagation in the resin-rich, inter-tow regions [44,45,46,47]. Voids are also one of the concerns for long-term durability of composites as they accelerate moisture uptake [48].…”

Section: Resultsmentioning

confidence: 99%

Fabrication of High Quality, Large Wet Lay-Up/Vacuum Bag Laminates by Sliding a Magnetic Tool

et al. 2018

View full text Add to dashboard Cite

This study presents a novel method to fabricate high-quality, large composite parts which can be used in a wet lay-up/vacuum bag (WLVB) process. The new method utilizes a commercial lifting magnet, which is commonly used for transporting ferrous plates, to apply a magnetic consolidation pressure on the WLVB composite lay-up. The pressure is applied on a large area of the laminate by slowly sliding the magnet over the vacuum bag surface, which leads to an improved laminate quality. When further improvement is desirable, multiple passes of the magnet can be performed, where each pass successively compacts the lay-up. To explore the feasibility of implementing this technique, random mat and plain weave glass/epoxy laminates were fabricated, and their properties compared to conventional WLVB laminates. The effects of the number of moving passes of the lifting magnet on the laminate microstructure and properties are also investigated. As a result of multiple passes, the fiber volume fraction in random mat and plain weave laminates increases to 34% and 53%, representing 80% and 16% improvements, respectively. In addition, the void volume fraction reduces almost by 60% to a very low level of 0.7% and 1.1%, respectively. Consequently, the flexural properties considerably enhance by 20–81%, which demonstrates the potential of the proposed method to produce WLVB parts with substantially higher quality. It is also shown that there exists an optimal number of passes, depending on the fabric type where additional passes induce new voids as a result of excessive resin removal.

show abstract

Section: Resultsmentioning

confidence: 99%

Fabrication of High Quality, Large Wet Lay-Up/Vacuum Bag Laminates by Sliding a Magnetic Tool

et al. 2018

View full text Add to dashboard Cite

show abstract

“…Voids are formed primarily due to entrapped air within carbon fibre/epoxy prepreg prior to lay-up and aqueous volatiles emitted from the resin during the cure stage. 27,28 According to the TGA-based methodology, the void content can be obtained by equation (2). Figure 4(d) presents the relationship between the different curing processes and void content of composite laminates.…”

Section: Resultsmentioning

confidence: 99%

Evaluating random vibration assisted vacuum processing of carbon/epoxy composites in terms of interlaminar shear strength and porosity

Yang

Zhan

Jiang

et al. 2019

Journal of Composite Materials

View full text Add to dashboard Cite

In the manufacturing process of carbon fiber-reinforced plastics composites, if the cure pressure that can form the hydrostatic pressure of resin is transferred inhomogeneously to the interior of composite structures, the critical imperfections such as voids and delamination which damage the mechanical properties and restrict subsequent use will be formed. Therefore, the present work reports the experimental research and analysis on the effect of random vibration applied to the curing system of carbon fiber-reinforced plastic laminates, mainly aiming at the reduction of the void content and improvement of mechanical performance under the vacuum pressure. The range of acceleration of vibrations was covered from 5 g to 15 g, for different periods of random vibration. Conducting a facile thermogravimetric analysis-based methodology, the influence of random vibration on the composite density, fiber volume fraction and void content of carbon fiber reinforced plastic laminates was analyzed. And the influence of voids on the interlaminar shear strength of materials was compared in terms of the initiation and propagation of interlaminar failure. In addition, the scanning electron microscopy was employed to observe the fracture surfaces of the composite specimens, which confirmed the different behaviors of fiber–matrix interface of various curing processes. The major benefits of the current research are that, the application of random vibration during the curing process can better wet through fibers by resin and increase the fiber volume fraction while reducing the bubbles and volatile gas of composite laminates at the same time.

show abstract

“…The methodology highlighted in Refs. 23,24 was adopted in order to investigate the effect of random vibration on the development and morphology of voids at four pre-defined points in time within the cure cycle, as shown in Figure 2(b). Laminates were labeled L 1 , L 2 , L 3 , and L 4 , which corresponded to the end of the first ramp, 15 min into the 80°C hold, 30 min into the 80°C hold, and the end of the second ramp, respectively.…”

Section: Methodsmentioning

confidence: 99%

Effect of random vibration-assisted vacuum processing on void development and interfacial properties in composites

Yang

Zhan

Jiang

et al. 2019

Journal of Reinforced Plastics and Composites

View full text Add to dashboard Cite

Voids and delamination are viewed as significant defects in the manufacturing process of carbon fiber-reinforced plastics structures and have been demonstrated to reduce the final performance of composites. Vibration is increasingly applied in new processing technologies for reducing void content and improving performance under low cure pressures. Therefore, this study investigates the effect of random vibration on the formation of voids during the curing process and the final interfacial properties of composite laminates. A 10 g random vibration was applied in the curing cycle, and a no-vibration cure cycle was designed as the experimental control group. The cure cycles were interrupted at pre-defined stages for each process to enable the in situ behavior of void content and growth of voids to be studied. Then the short-beam three-point bending test was employed to determine the interlaminar shear strength of composite samples. And the interlaminar cracks and fracture surfaces of tested specimens were captured by scanning electron microscopy. Besides, the interfacial shear strength of composite samples was measured by single-fiber push-in test. Compared with static group, the major benefits of the current research are that the growth of voids was impeded and void content was decreased obviously at each stage in composite samples produced by random vibration-assisted vacuum processing. In addition, the final interfacial properties were improved at the macro and micro levels due to adequate adhesion of the fiber–matrix interface when random vibration was introduced into the curing cycle.

show abstract

Rapidly cured out-of-autoclave laminates: Understanding and controlling the effect of voids on laminate fracture toughness

Cited by 17 publications

References 23 publications

Fabrication of High Quality, Large Wet Lay-Up/Vacuum Bag Laminates by Sliding a Magnetic Tool

Fabrication of High Quality, Large Wet Lay-Up/Vacuum Bag Laminates by Sliding a Magnetic Tool

Evaluating random vibration assisted vacuum processing of carbon/epoxy composites in terms of interlaminar shear strength and porosity

Effect of random vibration-assisted vacuum processing on void development and interfacial properties in composites

Contact Info

Product

Resources

About