Papers by Keyword: Thermoset

Abstract: Thermosets play an important role in composite processing, adhesive bonding and coating. In all these applications, shrinkage my cause a significant amount of residual stress, leading to distortion, reduced load carrying capacity and cracking. The chemical curing reaction is accompanied by a reduction in volume called “chemical shrinkage”. If curing is performed at elevated temperature, cooling to ambient conditions afterwards is accompanied by “thermal shrinkage” and further shrinkage due to so-called “physical ageing”. A skillful combination of available methods makes it possible to separate chemical shrinkage in the viscous state from shrinkage in the gelled and vitrified state. Modeling of the time-and temperature-dependent properties is the prerequisite for the prediction and control of residual stresses caused by shrinkage in thermoset polymers.

Abstract: The shift towards electric mobility needs extensive research into battery modules, particularly in relation to safety due to the high energy density of Li-ion batteries. Battery casings must be able to protect the module from external impacts while also containing any potential danger in the event of internal failure. This study presents a comprehensive qualitative screening of thermoset and thermoplastic carbon fiber-reinforced polymers (FRP) used in automotive and aerospace applications under thermal runaway (TR) conditions, to identify suitable materials for battery enclosures. The test setup is an adaptation of the UL 2596 standard with a hexagonal array of seven 21700-format cells. The results indicate that CF-PEEK, CF-PPS, and an aerospace-grade epoxy, CF-EP_str (primary structural material) effectively contain the TR with low damage using the current setup. Medium damage was observed in CF-PC, CF-bio-based phenolic, while non-structural CF-epoxy and CF-PA6 failed to contain the TR. This qualitative study serves as an initial screening process to narrow down materials for further in-depth analysis, emphasizing the need for reproducible TR events for accurate assessment.

Abstract: Piezo-chromic oxides are able to mark pressure or strain by a drastic color change. In this paper, CoMoO4 molybdate compound and related thermoset composites were prepared in lab. The distribution of CoMoO4 oxide in the thermoset matrix was first investigated via SEM. Moreover, the effects on the thermal and mechanical properties with the addition of CoMoO4 oxide were further analyzed. The piezo-chromic characteristic for CoMoO4 incorporated thermoset composites were verified with compression test. The color change can be clear visualized at a strain level close to the yield point of the composite blends. This study has the potential to open new directions to piezo-chromic polymeric materials as early damage detector.

Abstract: In this study, a renewable phenolic component was synthesized using empty fruit bunch fibers via microwave-assisted liquefaction known as Liquefied Empty Fruit Bunch (L_EFB). L_EFB can be used as phenolic derivative to replace petroleum-based phenol as it contains aromatic group in lignin that can be used as starting materials to synthesis polybenzoxazine resins. A Lignin-based benzoxazine (L-PBz) has been synthesized using a solventless approach from the reaction of L_EFB, furfurylamine as the amine component and paraformaldehyde via Mannich condensation reaction. Two different ratios of L_EFB:furfurylamine:paraformaldehyde which are 1:1:1 and 1:1:2 were investigated. The thermal properties and polymerization behavior of the L-PBz were analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. In addition, cured-polybenzoxazine composites were also prepared by hot-pressing the uncured L-PBz at 250 °C for 4 hours, and the mechanical properties of the composites were assessed through Izod impact strength test. TGA analysis showed that, L-PBz with ratio of 1:1:1 exhibit a high char yield compared to 1:1:2 which is 47% vs 43%, respectively, after being heated until 900 °C. However, L-PBz with ratio of 1:1:2 showed good polymerization behavior compared to 1:1:1 which indicated by the curing temperature 215 °C vs 238 °C. L-PBz composites, which added with cellulose nanocrystal (CNC) fillers have better strength compared with the absence of fillers. As a conclusion, the aromatic structure of lignin in empty fruit bunch fibers has presented a promising alternative to replace petroleum-based phenol in polybenzoxazine synthesis.

Abstract: New bio-based thermoset resin was synthesized by blending unsaturated polyester (UPE) and epoxidized palm oil (EPO) together with layered silicate nanoclay (MMT). The biobased polyester resin was processed by 1.5phr benzoyl peroxide initiator. In this study, EPO was added at 10 wt%, while the layered silicate added at 1, 1.5 and 2 phr. The MMT nanoclay was sonicated with acetone for two hours and followed by adding UPE. The MMT, acetone and UPE solution were then dried on a hot plate for 24 hours and followed by vacuum oven for 30 minutes. Then, the EPO and styrene were added to the solution. The sample was cured in an oven at 100 °C (2 hours) and followed by post curing at 160 °C (2 hours). Flexural properties of the UPE/EPO bioresin were experimentally characterized. It was found that, addition of nanoclay improved the flexural modulus of UPE resin. However, the dropped modulus of the resulted bioresin was not recovered by the addition of up to 2 phr MMT. Addition of low percentage MMT nanoclay, which was 1 phr gave a very significant improvements on the dropped flexural strength of UPE/EPO bioresin. The distribution of the MMT nanoclay in the UPE/EPO bioresin sytem was further analysed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) images.

Abstract: In this paper, conducting polymer composites were prepared by adding different percentage of carbon black (2, 4, 6 and 8)% to unsaturated polyester resin. Hence, this project focuses on two types of carbon black which is commercially available that is activated carbon black and carbon black produced internally from water hyacinth. Their effect on the electrical properties of the polyester compositewas analyzed. The A.C. electrical conductivity of the polyester composite was studied using Precision LCR meter. The A.C. electrical conductivity of polyester-carbon black composite has been investigated at a frequency ranging from 50 Hz to 1 MHz. The result showed that the electrical conductivity ofthe composite was changing with different concentration of carbon black. It has been observed that the electrical conductivity of the composite is frequency dependent and increases with increasing percentage of carbon black fillers in the polyester composite.

Abstract: In this paper a new variable forming tool concept and associated numerical methods for calculating optimal actuator layout and estimating CFRP part quality are presented. The concept of the tool features a modular design and active control of the forming process to achieve the desired geometry. Initially the laminate is placed on the flat top layer of the forming tool. There it is fixed and compacted using vacuum bagging. After compacting, it is heated up to increase the performance of the forming process using water based tempering of the forming tools top layer. The heated laminate is then formed, pulling the tools top layer into the desired geometry using the actuators. Finally, the formed laminate is cooled and transferred into a mold for curing. The position of the forming tools actuators on the base plates is variable. Numerical optimization in combination with finite element (FE) technologies is utilized, to approximate the tool surface within given error margins, with as few actuators as possible. In addition, results of a numerical method for part quality estimation are shown. The influence of the forming process on mechanical properties due to fiber waviness is taking into account using a self-developed method that includes manufacturing characteristics in FE modeling of the part. The method is based on mathematical descriptions of fiber waviness, which are implemented into a FE model. Therefore a structure discretization assuming perfect fiber orientations is realized and the expected fiber waviness induced by the forming process is applied element-wise.

Abstract: New bio-based thermosetting resin was synthesized from palm oil. In this study the epoxy groups presented on the epoxidized palm oil (EPO) were first acrylated and then further maleinized. The acrylation reaction was done by introducing acrylic acid into epoxy group of the epoxidized palm oil. Hydroquinone and triethylamine were used as inhibitor and catalyst, respectively. This reaction was confirmed by Fourier Transform Infrared Spectroscopy (FTIR). To render acid groups on the resulting monomer, the acrylated epoxidized palm oil (AEPO) was further reacted with maleic anhydride. The resulting maleinated acrylated epoxidized palm oil (MAEPO) was characterized by FTIR and Nuclear Magnetic Resonance Spectroscopy (¹H NMR).

Abstract: Effects of the incorporation of untreated and treated hybrid kenaf/carbon fibre reinforced epoxy composites on the impact properties were studied. Hybrid kenaf/carbon fibres and thermoset matrices were hand-laid up and characterized in terms of its mechanical properties. The kenaf fibres were alkali treated whilst the carbon fibres were gamma radiation treated before use as reinforcement in the epoxy resin matrix. The reinforcing effects of kenaf hybridized with carbon fibre in epoxy composites were evaluated at various fibre loadings with overall fibre contents 20 wt%. Hybrid composites with different ratios of kenaf fibre : carbon fibre ; 0.9:0.1, 0.8:0.2, 0.7:0.3 and 0.6:0.4 were prepared. Impact tests of untreated and treated hybrid kenaf/carbon fibres were performed. The fractured surfaces of these composites were investigated by using scanning electron microscopic technique (SEM) to determine the interfacial bonding between the matrix and the fibre reinforcement. It was found that the treated hybrid composites increased the impact strength by 26% compared to the untreated ones.

Abstract: Technique of including an amorphous thermoplastic film as the outermost layer of thermoset composites have been developed to join the thermoset composites using fusion bonding methods. Based on a WLF temperature dependence and a time dependence of t^1/4, isothermal and non-isothermal models were developed to relate the recovery of bonding strength to welding temperature and time. The isothermal model failed to take into account the time taken for the bonding interface to reach the glass transition temperature and final desired bonding temperature and lacked predictive power for experiments with short bonding times and low shear strength recovery. The non-isothermal model provided an excellent fit to the experimental date, showing a significant improvement over the isothermal model.