Materials Science Forum Vol. 813

Abstract: Shape memory polymers (SMPs) have drawn wide attention of many researchers for its potential applications to shipping industry, aerospace, bionics engineering and mechanical engineering. Shape memory polymers composites (SMPCs) have ability to improve the properties and obtain attain new functions of shape memory polymers. In this paper, trans-1, 4-polyisoprene reinforced by carbon fiber is developed to improve the mechanical weakness of trans-1, 4-polyisoprene bulk. Composites with carbon fiber weight fraction of 5%, 10%, and 15% are fabricated by casting samples with an average length of 2 mm. The mechanical property of the trans-1, 4-polyisoprene reinforced by short carbon fiber is evaluated and the effects of short carbon fiber on shape memory behavior are investigated. The results indicate that there is an optimum fiber weight fraction between 5 and 15 wt% where exists an extremely low recovery ratio, re-crystallizing temperatures (T_c) and an extremely high tensile stress.

Abstract: A fatal disadvantage of continuously reinforced thermoplastic composites is the high melt viscosity of the matrix which hampers impregnation. However, the melt viscosity of low molecular weight CBT resin can reach extremely low value, which simplifies impregnation and enables the use of thermoset production methods. The thermal analysis, rheological analysis and mechanical property on the polymerization and crystallization of CBT into poly (cyclic butylene terephthalate) (PCBT) at different ratios of catalyst were investigated in this paper. The continuous glass fiber (GF) reinforced PCBT composite with over 70% fiber volume content was prepared via in situ polymerization, and the mechanical property of the PCBT was studied. The best impregnation time was decreased and the degree of crystallinity was increased respectively with catalyst fraction increasing. The tensile/flexural strength and modulus of PCBT resin and GF/PCBT composites were enhanced when the catalyst fraction increased from 0.3% to 0.6%.

Abstract: This work is part of an ambitious project aiming to manufacture epoxy-glass leaf spring by microwave processing. Physical properties of final products to be manufactured, in particular the mechanical properties, are directly dependent on uniform repartition of microwave source heating during the treatment. The major problem in microwave processing, however, is attenuation of microwave source. We propose Dielectric Effect of Attenuation Inversion of the Electromagnetic Waves (DEAI) as a new way for uniform treatment of epoxy glassmicrowave energy. This solution utilizes dielectric properties of the mold to control the microwave heat source attenuation into the composite to be treated. Electromagnetic modelling of microwave process was carried out and validated by experimental results. The results show that microwave source heating attenuation can be controlled and inversed. We demonstrated uniform treatment on epoxy-glass parts ca. 100 cm long by means of compensation of microwave source attenuation.

Abstract: For the purpose of preparing stern bearings adapted to water-lubricating environment to replace natural lignumvitae, preparing bearings with solid lubricant of electromechanical equipment applied in some industries such as textile, food and healthcare to replace sintered bronze, and preparing advanced automotive upholstery, appliance and artware to replace natural rosewood and ox bone, three published patents including “a preparation method of artificial lignumvitae” were used to prepare artificial lignumvitae with a better wear resistance than natural lignumvitae. As the materials for sliding bearing, the main performance of artificial lignumvitae meets the requirement for sintered bronze FZ2365. It explores a new way to develop functional biomass materials with wood waste in urban and rural area while ensure its high quality and cleanness.

Abstract: Polymerized cyclic butylene terephthalate (pCBT) resin casts filled with short carbon fibers were prepared by the melt-mixing approach. The electrical conductivity of short-carbon-fiber (SCF) reinforced thermoplastic pCBT resin casts were investigated with a special attention paid to the properties in the percolation threshold region and the mechanical properties of the composites were also studied. The percolation threshold value of the novel material system was determined which was also verified by SEM images and the thermoelectric behavior of the specimens. Even though the electrical properties of SCF/pCBT composites enhanced significantly, the material becomes more brittle than neat pCBT and all the specimens appear brittle fracture during the mechanical test. Moreover, fiber pull-out is the main damage form in three-point-bending test.

Abstract: Surface mechanical attrition treatment (SMAT) is an excellent method to get nanocrystalline and nanotwinned ultrafine crystalline steels from coarse-grained AISI 304 stainless steel. Due to their outstanding mechanical properties, they both appear to be relevant candidates for ballistic protection of marine engineering. Comparing their ballistic performance against coarse-grained steel, as well as identifying the effect of the hybridization with a carbon fiber–epoxy composite layer have been done by Jaime Frontan et al. Hybridization is proposed as a way to improve the nanocrystalline brittle properties in a similar way as is done with ceramics in other protection systems. Dur to the limit of experimental equipment, there are many results which are hardly got. In this paper, a numerical method with Johnson–Cook flow stress model, user material subroutine VUMAT and surface-based cohesive behaviour is presented.

Abstract: Strength and ductility are very important to marine engineering. Because of their remarkable mechanical properties, nanocrystalline metals have been the focus of much research in recent years. Based on surface mechanical attrition treatment (SMAT) and warm co-rolling technologies, the resulting material performances amazingly exhibit high strength and exceptional ductility. Therefore, this method is a promising avenue for advanced materials for marine engineering. Cohesive finite element method (CFEM) is employed to investigate the tensile performance of multi-layer SMATed alloys. With the results of simulation and experiment compared, simulation parameters have been studied . According to comparing different simulation results, the model parameters, normal direction strength and tangential direction strength in CFEM are studied.

Abstract: In order to improve the interfacial properties in carbon fiber (CF) reinforced epoxy (EP) composites, we directly introduced amidized carbon nanotubes (CNTs) dispersed in the fiber sizing onto the fiber surface. Morphology and surface energy of CFs were examined by scanning electron microscopy (SEM) and dynamic contact angle analysis test (DCAT). Tensile strength (TS) was investigated in accordance with ASTM standards. Mechanical properties of the composites were investigated by interlaminar shear strength (ILSS) and impact toughness. Test results indicate that TS, ILSS and impact toughness were enhanced simultaneously.

Abstract: Surface Mechanical Attrition Treatment (SMAT) process, as one of the typical severe plastic deformation technologies, can be utilized to generate layup structure with finer size of grains and large residual stresses at the near treated surface area on the alloys. Such technology not only improves the mechanical behaviors but also keeps neatness of alloys without inducing extra compositions. In this paper, four major controllable parameters of SMAT process are investigated to demonstrate their influence on ball-impacting intensity of the treatment, which the improvement of mechanical behaviors are greatly dependent on. The high speed camera is employed to capture the motion of the balls and measure the impact velocities by counting the number of frames. The compared results indicate that the amount of balls not only varies the average velocities during SMAT process, but also offsets the effect of distance between treated surface and source of balls. In addition, the influence of ball sizes, the mentioned distance and power of excitation exhibits apparently on intensity of SMAT process when limited amount of balls are used.

Abstract: The effects of fiber orientation and volume fraction on electrical conductivity of unidirectional carbon fiber reinforced polymer (CFRP) were investigated. The unidirectional CFRP shows strong anisotropy in electrical properties. Composites with higher fiber volume fraction possess higher electrical conductivity, since the fibers are the only current path in the composites. Additionally, carbon nanotubes (CNTs) were mixed into the resin by high-pressure microfluidizer to improve the electrical properties of the composites. Results show that the electrical conductivity of the polymer matrix has been dramatically improved. The conductivity of CNTs modified CFRP composites is improved along fiber direction, while it remains at the same level in the transverse to fiber direction.