Microwave curing of multidirectional carbon fiber reinforced polymer composites

Microwave curing technologies have many advantages in manufacturing fiber reinforced polymer composite materials used in aerospace products, compared with traditional autoclave curing technologies. However, multidirectional carbon fiber reinforced polymer composites can hardly be penetrated and heated by microwave directly, which has become a major obstacle in industrial application worldwide. In this paper, an indirect microwave curing method was proposed to solve this problem. The microwave absorption performance of the indirect microwave heating medium was systematically optimized by evaluating its dielectric properties and reflection loss according to the transmission line theory. On this basis, the microwave susceptive mold was carefully designed and manufactured. Subsequently, the multidirectional carbon fiber/epoxy composite was successfully cured with indirect microwave heating, which was demonstrated by the observation of the curing process with infrared thermal imager and differential scanning calorimetry analysis of the final products. Compared with the traditional thermal curing method, the curing cycle and energy consumption were reduced by 42.1% and 75.9% respectively. Results of further characterization experiments indicated that the mechanical properties of indirect microwave cured specimens were slightly higher than those of the thermally cured counterparts.

Curing multidirectional carbon fiber reinforced polymer composites with indirect microwave heating

Recent development of microwave applications for concrete treatment

Carbon fiber reinforced plastic self-resistance electric (SRE) heating has been conceived as an alternative to out-of-autoclave technology due to its characteristics of uniform heating, fast heating/cooling, low energy consumption, and low equipment investment. In this work, a series of SRE heating experiments were conducted, in which the temperature distribution field, energy consumption, and curing time of SRE curing process were characterized. Comprehensive mechanical tests and microscopic characterization were carried out. The experimental results exhibit that the rapid heating rate of SRE curing process resulted in a weaker matrix performance because of the insufficient time of void elimination, which finally leads to an inferior compression and flexural strength for the composite part, while the fiber preferential heating effect can significantly improve the fiber-resin interfacial strength, because the naturally formed temperature difference along the interfacial area enhanced the adhesive strength of the resin around the interface, which improved the macroscopic tension and interlaminar shear strength.

Mechanical performance of carbon fiber/epoxy composites cured by self-resistance electric heating method

Search for novel energy-efficient, eco-friendly, and time-saving manufacturing techniques has gained momentum in the recent times. Polymer composites have been increasingly adapted for variety of industrial applications, however, their efficient processing remains challenging. Microwave curing technique has been employed to process thermoset-based composites since 1980, however, processing of thermoplastic-based composites with natural-fibers as reinforcement, calls for additional data and hence investigations. The current work presents an overview of the basics of microwave heating and the physics behind the microwave processing of polymer composites. A state-of-the-art on microwave processing of thermoset and thermoplastic-based composites and developments in microwave joining has been reviewed. The major constraints in adopting microwave technology for curing composites at the industry scale are highlighted. The article also highlights the challenges during microwave processing of sustainable thermoplastic-based polymer composites. Future scope of work to 3D print the polymer matrix composite parts, through microwave scanning route has been indicated. 

Processing of polymer matrix composites using microwave energy: A review

Microwave curing technologies have many advantages in manufacturing fiber reinforced polymer composite materials used in aerospace products, compared with traditional autoclave curing technologies. However, the uneven electromagnetic field of microwave in the cavity of the curing chamber results in uneven temperature on the surface of composite laminates during curing, which has been a major obstacle in industrial applications worldwide. Existing methods attempted to solve the problem by the random superposition of uneven electromagnetic fields, but the results were still not satisfactory to meet the high quality requirements of aerospace parts. This paper reveals the one-to-one correspondence between heating patterns of composite parts and microwave curing system settings, and reports a new concept to solve this problem by continuously monitoring and compensating the uneven temperature distribution in real-time. Experimental results from both fiber optical fluorescence sensors and infrared thermal imagers showed significant improvement in temperature uniformity compared with existing methods.

/pdf/a-multi-pattern-compensation-method-to-ensure-even-4eyt1wtfe1.pdf

A multi-pattern compensation method to ensure even temperature in composite materials during microwave curing process

Zone-regulated microwave heating of CFRP laminates via ultrathin and flexible resonance structures with different working frequencies

The present invention provides a microwave heating temperature uniformity active control method based on heating mode complementation on the basis of discovering that different microwave system arrangements (comprising the number, the positions and the frequencies of microwave sources, the shape, the size and filling dielectric of a microwave cavity body, materials, shapes and sizes of parts, and the positions of the parts in the microwave cavity body, etc.). The method performs preheating of parts to be heated to obtain heating modes through arrangement of different microwave systems, can monitor temperature distribution in the microwave heating system in real time, perform automatic matching complementation heating modes for non-uniform temperature distribution to regulate arrangement of the microwave systems in real time and perform active compensation for the non-uniform temperature distribution. The microwave heating temperature uniformity active control method based on the heating mode complementation breaks through the difficulty in non-uniform heating of microwave in principle so as to greatly improve the temperature uniformity of parts in the microwave heating process.

Microwave heating temperature uniformity active control method based on heating mode complementation

A method for active control of microwave heating temperature uniformity based on heating mode complementarity. The method comprises: preheating a component to be heated in order to acquire the heating mode of the component under different microwave system setup parameters; during the microwave heating process, monitoring in real-time the temperature distribution of the same layer of material of the component; for uneven temperature distribution, automatically matching complementary heating modes and adjusting in real-time the microwave system setup parameters; and thereby performing active compensation of the uneven temperature distribution. The present invention in principle overcomes the problem of uneven microwave heating, and greatly improves the temperature uniformity of a component during a microwave heating process.

Shaochun Sui

Papers

A multi-pattern compensation method to ensure even temperature in composite materials during microwave curing process

Zone-regulated microwave heating of CFRP laminates via ultrathin and flexible resonance structures with different working frequencies

Microwave heating temperature uniformity active control method based on heating mode complementation

Method for active control of microwave heating temperature uniformity based on heating mode complementarity