Quickstep Processing Research Articles

Aerospace composite cured by quickstep and autoclave processing techniques: Evaluation and comparison of reaction progress

Quickstep is relatively a new technique for aerospace composite processing. Thermoset resins (prepregs) have been frequently designed by autoclave method requiring low ramp rate curing of 2–3 K min−1. However, ramp rate up to 15 K min−1 has been achieved via Quickstep processing. This technique allows alteration in chemo-rheology of resin system and so influences the reaction progress. In this attempt, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA) were used to monitor the cure progress of 977-2A epoxy resin and carbon fiber reinforced composite. The curing reaction progress of 977-2A epoxy/carbon fiber was considered for the first time by comparing Quickstep processing and autoclave method. According to DSC results, the reaction progress in Quickstep technique was comparable to that of autoclave curing. Moreover, DMTA of Quickstep cured samples showed increase in glass transition temperature (Tg) due to increased cross-linking density at greater hold time (upper cure temperature). FTIR was used to monitor the conversion of representative functional groups versus applied Quickstep and autoclave curing steps. The structural analysis depicted that the Quickstep curing path for 977-2A resin was different than the autoclave curing; however the final cross-linked structure was similar to that of autoclave cured samples.

Cure characterization of Cycom 977‐2A carbon/epoxy composites for quickstep processing

In this effort, Quickstep, a relatively a new technique, have been employed for manufacturing of composite materials. The cure schedule provided by a prepreg manufacturer is usually designed for autoclave or other traditional processing techniques and thermosetting resin systems are formulated for ramp rate curing 2–3 K min−1. While in case of Quickstep processing, ramp rates of 15 K min−1 can be achieved, thus changing the chemorheology of resin. The cure process of 977‐2A carbon/epoxy composites was evaluated for Quickstep processing using differential scanning calorimetry (DSC), dynamic mechanical and thermal analysis, and Fourier transformed infrared and results were compared with cure cycle employed for autoclave curing. Optimum hold time for Quickstep processing at upper curing temperature (180°C) was determined using DSC. The hold time of 120 min at 180°C was found to be suitable for Quickstep cure cycle, producing a panel of similar degree of cure to that achieved through autoclave processing schedule. Final degree of cure was dependent on time spent at upper cure temperature and slightly on initial steps of the cure cycle which was used to control the resin flow, fiber wetting, and void removal. Quickstep processed samples exhibited higher Tg and crosslink density and similar molecular network structure to the autoclave cured samples. POLYM. ENG. SCI., 54:887–898, 2014. © 2013 Society of Plastics Engineers

Effect of double vacuum bagging (DVB) in quickstep processing on the properties of 977‐2A carbon/epoxy composites

An aerospace grade prepreg 977‐2A carbon/epoxy composite was processed using traditional oven/autoclave and relatively new technique, Quickstep (QS). The manufacturer's recommended autoclave cure cycle was employed for oven/autoclave processing while due to greater flexibility to control the cure cycle temperature in order to manipulate the resin viscosity, several cure cycles were employed for Quickstep processing. Optimization methodology and effect of these cure schedules and their comparison with traditional oven/autoclave curing is presented in previously published article. However, in order to reduce the total cycle time of QSAD (QS‐60) cure schedule, an attempt was made to facilitate the excess resin to squeeze out during QS‐35 and QS‐45 cure. This attempt was based on the incorporation of double vacuum bagging (DVB) technique into Quickstep processing. Statistical analysis was performed to investigate any effect of DVB in Quickstep processing and it was observed that incorporation of DVB in Quickstep processing is not found to be significantly effective, however, it is believed that small resin rich patches of QS‐45 cured panels can be removed with controlled application of external pressure using DVB. POLYM. COMPOS., 34:942–952, 2013. © 2013 Society of Plastics Engineers

Determination of optimum cure parameters of 977‐2A carbon/epoxy composites for quickstep processing

AbstractIn this study polymer‐matrix composite has been processed using autoclave and Quickstep techniques. A phenomenological approach was adopted for the optimization of cure cycle for Quickstep of an aerospace grade epoxy composite (Cycom 977‐2A carbon/epoxy prepregs). Though there are reports concerning the processing and properties of materials using Quickstep technique, little work has been reported on the design of optimized cure cycle for Quickstep processing based on rheology, ultrasonic testing, and mechanical characterization. A step by step account is provided in this study, describing the introduction, balancing and combination of isothermal dwell periods and temperature ramps in order to control the resin viscosity. All the panels manufactured were qualitatively assessed using ultrasonic C‐scan and afterwards fiber and void content, panel thickness, flexural strength, and interlaminar shear strength (ILSS) were assessed and compared with those obtained from traditional autoclave‐ and oven‐cured laminates. The Quickstep panel properties produced from optimized cure cycle was superior to oven curing and was comparable with autoclave. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effect of manufacturing process on the flexural, fracture toughness, and thermo-mechanical properties of bio-composites

This study evaluated the performance of jute reinforced polyester bio-composites cured with an out-of-autoclave curing process, Quickstep™. The mode I fracture toughness (GIc), flexural, and thermo-mechanical properties of the composites were measured for cure cycle times of 5, 30, 60 and 90 min at an optimum cure temperature of 95 °C, and were compared to a reference composite laminate cured at room temperature. Generally, the Quickstep process was found to improve the degree of cure by up to 55% and the resistance to crack propagation of the resulting composites was found to be more stable. A balance in properties was obtained after 30 min of cure where an improvement in thermo-mechanical and fracture properties was observed, but on the other hand, was accompanied by a decrease in flexural strength and modulus compared to the reference sample. Shorter (i.e. 5 min) and longer cure cycle times (above 30 min) used by the Quickstep were found to be detrimental to the properties of the resulting composites.

Hygrothermal degradation of 977-2A carbon/epoxy composite laminates cured in autoclave and Quickstep

While there are reports concerning the processing and properties of materials using Quickstep technique, little attention has been paid to the hygrothermal degradation of the flexural, interfacial and glass transition behaviours of polymeric composites cured at a relatively high ramp rate of 10 K min −1 (typical of Quickstep processing). Composite laminates were manufactured in an autoclave and using Quickstep and then conditioned in a climatic chamber at 70 °C and 85% RH until reaching the limit of saturation. The interfacial (interlaminar shear strength (ILSS)), flexural (flexural strength) and glass transition ( T g ) properties of the conditioned and unconditioned panels were evaluated. The results demonstrated that the moisture absorption caused the deleterious effect on the properties and that the reduction in the flexural, interfacial and glass transition properties of Quickstep panels was comparable to that observed in autoclave cured panels. Thermal stability, reversible and irreversible effects of hygrothermal conditioning using TGA, DMTA and FT-IR spectroscopy was also investigated and discussed.

Quickstep processing to control exothermic reaction during the manufacture of thick laminates

The present research is based on the manufacturing of thick laminates using qualified, aerospace grade prepreg and liquid resin material. After optimising the cure cycle including control over the exothermic reaction, 30 and 50 mm thick laminates were manufactured from both the selected materials and analysed for manufacturability, exothermic reaction and laminate quality. During the curing cycle, temperature was monitored at different sections of the laminate, namely, top, middle and bottom. From the results obtained, it can be confirmed that, curing under the Quickstep processing conditions enables manufacturing thick laminates very rapidly and without the exothermic reaction. This saves tremendous amount of time and avoid wastage of large and costly components.

Manufacturing Influence on the Delamination Fracture Behavior of the T800H/3900-2 Carbon Fiber Reinforced Polymer Composites

‘Torayca’ T800H/3900-2 is the first material qualified on Boeing Material Specification (BMS 8-276) which utilizes the thermoplastic-particulate interlayer toughening technology. Two manufacturing processes, the autoclave process and the fast heating rated Quickstep™ process, were employed to cure this material. The Quickstep process is a unique composite production technology which utilizes the fast heat transfer rate of fluid to heat and cure polymer composite components. The manufacturing influence on the mode I delamination fracture toughness of laminates was investigated by performing double cantilever beam tests. The composite specimens fabricated by two processes exhibited dissimilar delamination resistance curves (R-curves) under mode I loading. The initial value of fracture toughness G IC–INIT was 564 J/m2 for the autoclave specimens and 527 J/m2 for the Quickstep specimens. However, the average propagation fracture toughness G IC–PROP was 783 J/m2 for the Quickstep specimens, which was 2.6 times of that for the autoclave specimens. The mechanism of fracture occurred during delamination was studied under scanning electron microscope (SEM). Three types of fracture were observed: the interlayer fracture, the interface fracture, and the intralaminar fracture. These three types of fracture played different roles in affecting the delamination resistance curves during the crack growth. More fiber bridging was found in the process of delamination for the Quickstep specimens. Better fiber/matrix adhesion was found in the Quickstep specimens by conducting indentation-debond tests.

Effect of Cure Cycle Heat Transfer Rates on the Physical Properties of an Epoxy Matrix Composite

Although the autoclave technique produces composite parts of high quality, the process is time consuming and has intrinsically high capital and operating costs. QuickstepTM is a novel polymer composite manufacturing technique designed for the out-of-autoclave processing of highquality, low-cost components with a reduction in cure-cycle times. This paper assesses the use of the Quickstep method for the processing of an epoxy-carbon fibre aerospace composite material. The Quickstep process is compared both to a thermal vacuum-bag only process and the manufacturer’s specifications for autoclave cured panels. Higher process ramp rates, achievable by using Quickstep, have been shown to reduce resin viscosity and facilitate void removal. Through manipulation of the Quickstep cure cycle while the resin is at low viscosity, significant effects on the mechanical properties of the product are demonstrated. Using Quickstep curing it has been found that better interlaminar properties than the manufacturers autoclave data could be obtained while the flexural strength was a little lower. The work identifies key parameters associated with the Quickstep process giving an insight into how it can be optimised further in an attempt to produce panel properties that rival those produced by autoclave methods.

Effect of cure cycle heat transfer rates on the physical and mechanical properties of an epoxy matrix composite

Although the autoclave technique produces composite parts of high-quality, the process is time consuming and has intrinsically high-capital and operating costs. Quickstep™ is a novel polymer composite manufacturing technique designed for the out-of-autoclave processing of high-quality, low-cost components with a reduction in cure cycle times. This paper assesses the use of the Quickstep method for the processing of an epoxy/carbon fibre aerospace material and compares this to equivalent composites produced using an autoclave process. Higher process ramp rates, achievable using Quickstep, have been shown to reduce resin viscosity thus facilitating void removal. Manipulation of the Quickstep cure cycle, while the resin is at low-viscosity, has significant effects on the mechanical properties of the product whilst simultaneously reducing the cure cycle time. Using Quickstep curing, samples were produced exhibiting comparable interlaminar properties but lower flexural strength as compared to those produced using the autoclave. However, normalisation of the data to a common fibre volume fraction showed that better interlaminar shear strengths could be obtained using Quickstep. This improvement in specific interlaminar shear strength was postulated to be due to the lowering of the resin viscosity over the duration of the cure, resulting in better wet through of fibres by resin and improved interfacial adhesion between fibre and matrix. This study identifies key parameters associated with the Quickstep process, providing a basis for further optimisation.

Characterization and Analysis of Delamination Fracture and Nanocreep Properties in Carbon Epoxy Composites Manufactured by Different Processes

Delamination resistance and nanocreep properties of 2/2 twill weave carbon epoxy composites manufactured by hot press, autoclave, and Quickstep™process are characterized and analyzed. Quickstep is a fluid filled, balanced pressure heated floating mold technology, which is recently developed in Perth, Western Australia for the manufacture of advanced composite components. Mode I and Mode II interlaminar fracture toughness tests, and nanoindentation creep tests on matrix materials show that the fast ramp rate of the Quickstep process provides mechanical properties comparable to that of autoclave at a lower cost for composite manufacturing. Low viscosity during ramping process and good fiber wetting are believed to be the reasons that this process produces composites with high delamination and creep-resistant properties. Nanocreep properties are analyzed using a Kelvin–Voigt model.

University/industry partnership in transferring continuous process improvement technology

This case study describes a university's cooperation with a manufacturer in implementing a continuous process improvement program. Included in the case study are a description of the NIST Manufacturing Extension Program, the manufacturer, the QUICK STEP* methodology of continuous process improvement, a QUICK STEP case study, and the manufacturer's results from using QUICK STEP. The basic foundation of the QUICK STEP continuous improvement process is the compression of time in all ways possible from the receipt of an order through the receipt of payment. The university participated in the manufacturer's improvement process by assisting in the focus groups to conduct critical assessments, documenting the QUICK STEP process and providing real world learning experiences to students.