Dynamic Mechanical Characterization of Fiber Filled Unsaturated Polyester Composites

Relationship Between Powder Surface Characteristics and Viscoelastic Properties of Powder-Filled Semisolids

We investigate the response of the two-dimensional (2D) continuous non-particulate film of surfactant sorbitan tristearate confined at the air-water interface under oscillatory shear deformation. The time dependence of various rheological parameters show critical-like behavior at a value of strain amplitude close to the crossover point of elastic () and viscous () shear moduli. Imposing oscillatory shear of different strain amplitudes () above and below the crossover strain amplitude () over a large number of cycles, we quantify the temporal dependence of interfacial viscous modulus, phase angle () as well as higher harmonic components of stress. The number of shear cycles () required for these quantities to reach the steady state value diverges near . The steady state values of the third harmonic () show order parameter like behavior indicating the importance of higher order harmonics near the nonequilibrium transition. We further show that the energy dissipation per cycle per unit volume has a marked change near , consistent with continuum level nonequilibrium shear-transformation-zone model of amorphous viscoplasticity.

the determination of the surface shear properties of adsorbed protein layers

<div class="htmlview paragraph">The use of low-profile sheet molding compound (SMC) resins for automotive body panels is growing rapidly. Surface appearance and bonding capabilities are two major performance considerations for these body panel applications. The Owens/Corning Fibergias Atryl resin was developed specifically to meet these criteria. As with all SMC resin systems, specific formulations need to be developed for individual applications, therefore the effect of styrene, unsaturated polyester resin, and thermoplastic quantities are of major importance in formulations development. Prior to introducing this new resin system, these three parameters were varied as part of a designed experiment and studied as a function of both surface aesthetics and adhesive bonding.</div> <div class="htmlview paragraph">From a computer generated result, the Atryl resin system was optimized to provide both smooth surface and strong bondabillty. This optimized system was then compared to other automotive SMC Class A resin systems to confirm not only that the surface was improved but also adhesive, paint primer, and in-mold coating bondabillty were maintained. From this work, the Atryl resin system, based on Owens/Corning's unsaturated polyester and thermoplastic resins, was found to meet or exceed critical performance criteria as specified by the automotive original equipment manufacturers. Based on results achieved with the recommended sheet molding compound formulation, the Owens/Corning Atryl resin system has been given a generic approval by the CPC Group of General Motors Corporation.</div>

The term Sheet Molding Compound (SMC) is applied to composites formulated with unsaturated polyester resin (UPE), glass fibers as reinforcement and other additives: thickening agent, low profile agent, inorganic filler (CaCO3), etc. The understanding of the hydrothermal ageing effects of this material is an important factor for its improvement, because this heterogeneous material very easily deteriorates in the presence of humidity. The effect of this kind of ageing is analysed using dynamic mechanical thermal analysis. Our mechanical spectrometry results, show that the hydrothermal ageing produces two types of effects in our model class A SMC samples: firstly, some partially reversible physical effects associated, on the one hand, with the hydrophilisation of the UPE network and, on the other, with the thickening phenomenon (formation of coordinative bonds between the carboxyl groups of the ester linkages and the unsaturated Mg ions). Secondly, some non-reversible chemical modifications due to the partial hydrolysis of the low profile agent (a small amount of PVAc is transformed to PVA and to acetic acid).

This paper describes a laboratory experiment involving polyester composites, and especially sheet molding compounds (SMC), to investigate several aspects of composite science. The SMC contain an unsaturated polyester resin (blended with styrene monomer), fillers (calcium carbonate), and glass-fiber reinforcement. The mix also contains a peroxide catalyst and other additives. During the practical work, the reticulation reaction of SMC is studied by differential scanning calorimetry to optimize the conditions (temperature and time) of the molding process. The SMC are then molded by compression under a heating press. SMC composite appears to be a choice material for laboratory study because both chemistry and the molding process can be investigated.

Polymer/expanded graphite (EG) nanocomposites have great importance in many industrial applications mainly due to their high electrical/thermal conductivity or flame retardancy. However, to fully employ the benefits of polymer/EG nanocomposites one must consider the high degree of porosity of EG. The high degree of porosity of EG can deteriorate the composites’ mechanical properties if the polymer chains cannot diffuse completely into the EG pores. In this article, an insight is given into the diffusion of unsaturated isophthalic polyester (UP) resin, consisting of a combination of maleic anhydride and isophthalic anhydride in the resin backbone, with two viscosities, into the pores of the EG particles of various degrees of porosity. The diffusion experiments were carried out on compressed EG tablets with the same density but different porosity due to the different porosity of the EG particles. The results showed that the diffusion rate of the UP resin with higher viscosity slightly decreased when the EG porosity decreased but, in the opposite way, it strongly increased for the low viscosity UP resin. The EG nanocomposites samples were molded at varying pressures. The micrographs of the fractured surfaces of the EG nanocomposites showed that the EG pores were not filled with resin, thus the EG nanocomposites had residual pores. It was found that composites containing EGs with higher expansion ratio and larger particles and pores showed larger residual pores. Furthermore, the composites prepared with the more viscous UP resin showed more residual pores. By applying a pressure of 10 bar instead of 1 bar, a reduction of 7–20% in the residual pores of the nanocomposites was observed which led to improved mechanical properties by up to 20% in flexural strength for the EG with the highest expansion ratio.

Acute and chronic effects of static stretching of different target muscles on shear elastic modulus: A narrative review

The objective of this study is to improve the adhesion between SMC and EPDM Rubber without the application of a solvent-based adhesive. The influence of the addition of different percentages of phenolic resin, as an adhesion promoter, in the SMC, has been studied. The SMC was prepared in a conventional continuous SMC machine. The EPDM rubber was over-injected on the SMC part, and then vulcanized. The chemical bonding between both materials was produced during the rubber vulcanization step. The SMC-EPDM bond quality was characterized in different ways: 1) mechanically, determining the adhesion strength, 2) optically, comparing the surfaces of the SMC and the rubber after separating them, and 3) chemically, analyzing by DSC the heat of reaction of mixtures of rubber with the different resins used. It has been concluded 1) that SMC-EPDM adhesion is achieved with polyester resins but not with vinyl ester resins, 2) that the addition of phenolic resin promotes the chemical adhesion between SMC and EPDM rubber and 3) that the chemical bonding between both materials occurs because of the double bonds of residual maleic units of the polyester, which are more abundant when phenolic resin is added.

Lightweight sheet molding compound (SMC) composites containing cellulose nanocrystals

Muscle shear elastic modulus is linearly related to muscle torque over the entire range of isometric contraction intensity

This study presents a comprehensive non-destructive evaluation of a broad range of construction materials using the impulse excitation of vibration (IEV) technique. Tested specimens included low- and normal-strength concrete, fiber-reinforced concrete (with basalt, polypropylene, and glass fibers), lime mortars (NHL-2 and -3.5), plaster, and clay bricks (light and dark). Compressive and flexural strength tests complemented dynamic resonance testing on the same samples to ensure full mechanical characterization. Flexural and torsional resonance frequencies were used to calculate dynamic elastic modulus, shear modulus, and Poisson’s ratio. Strong correlations were observed between dynamic elastic modulus and shear modulus, supporting the compatibility of dynamic results with the classical elasticity theory. Flexural frequencies were more sensitive to material differences than torsional ones. Fiber additives, particularly basalt and polypropylene, significantly improved dynamic stiffness, increasing the dynamic elastic modulus/compressive strength ratio by up to 23%. In contrast, normal-strength concrete exhibited limited stiffness improvement despite higher strength. These findings highlight the reliability of IEV in mechanical properties across diverse material types and provide comparative reference data for concrete and masonry applications.

Experimental and numerical analyses of the tensile strength and mixed-mode fracture behavior of sheet molding compound plates

The waste produced by bamboo stick production processing was collected from a Vietnamese craft village and used as a source of microfibril cellulose (MFC) for a filler of unsaturated polyester (UP) resin based composites in this study. A mixture of MFC in UP was obtained by directly introducing the bamboo pulp into UP resin followed by a grinding process using a ball-grinding machine. A master batch method was also adopted for composite preparation, in which a high-content solution of MFC in UP resin was first fabricated and then diluted to prepare another solution with the desired content. Morphology and mechanical characteristics of UP resin based composites were investigated. Effect of different methods of preparation, such as hand lay-up and vacuum bagging methods, on the mechanical properties of glass fiber reinforced UP resin composites was also examined, showing that the tensile strength of composite materials with 0.3 wt% MFC was increased by 10.24% (for the hand lay-up method) and 19.62% (for the vacuum bagging method) when compared with the pristine composite material. The flexural strength increased from 192.40 MPa to 208.63 MPa and the impact strength increased by 19.6% from 158.28 kJ/m2 to 186.84 kJ/m2 for the hand lay-up method.

The use of fiber reinforced unsaturated polyester resin composites in the form of sheet molding compound (SMC), bulk molding compound (BMC) and preform molding exceeded 475 000 tons (approximately one billion pounds) in North America and Europe in 1995. Many applications were in the transportation industry such as automotive body panels, truck components and semi-structural parts (Table 1). Other applications are in sanitary ware (bathtubs, showers, sinks), applicances, business machines and electrical components.