Experimental Study on Statistic Failure Properties of Composite Considering Temperature Effect

Advanced composite has been widely used in many fields with high mechanical performance requirements. Aim to characterize the reliability of composite, a statistic failure model was established based on Weibull distribution. Strength tests at various temperatures were conducted under tensile, compressive and in-plane shear loading conditions. As the temperature rises from 25 °C to 180°C, the strengths at different loading conditions reduces by nearly 60% except that the longitudinal tensile one reduces by only 16%. Equivalent strength at reference temperature was obtained based on time-temperature superposition principle. Then, the model parameters were determined with transferred test data using the median rank method, and statistic characterizations of different strength properties were further studied. Results show that the failure probability of composite is independent of temperature. Among all the strengths, the longitudinal compressive strength possesses the smallest shape parameter and correlation coefficient R of the fitting result, which means the strongest randomness of failure.

Method of Equivalent Strength Conditions in Composite Structures Evaluations

It is important to know the error or the approximate solution when calculating the strength of elastic composite structures (bodies) using the finite element method (FEM). To construct a sequence of solutions according to the FEM is necessary for the evaluation of the approximation error. It involves the grinding procedure for discrete models. The implementation of the grinding procedure for basic models that take into account the inhomogeneous, micro-homogeneous structures of bodies within the microapproach requires ample computer resources. This paper proposes a method of equivalent strength conditions (MESC) to calculate the static strength of elastic bodies with a non-uniform, microuniform regular structure. The calculation of composite bodies strength according to the MESC is reduced to the calculation of isotropic homogeneous bodies strength using equivalent strength conditions. Adjusted equivalent strength conditions are used in the numerical implementation of the MESC. They take into account the error of the approximate solutions. If a set of loads is specified for a composite body, then generalized equivalent strength conditions are applied. The FEM-based calculation of composite bodies strength that follows the MESC using multigrid finite elements requires 103 ÷ 105 times less computer memory than a similar calculation using ground basic models of composite bodies. The provided example of strength calculation for a beam with an inhomogeneous regular fiber structure using the MESC shows its high efficiency. The main MESC implementation procedures are outlined.

Cradle-to-Gate Life Cycle and Economic Assessment of Sustainable Concrete Mixes—Alkali-Activated Concrete (AAC) and Bacterial Concrete (BC)

The negative environmental impacts associated with the usage of Portland cement (PC) in concrete induced intensive research into finding sustainable alternative concrete mixes to obtain “green concrete”. Since the principal aim of developing such mixes is to reduce the environmental impact, it is imperative to conduct a comprehensive life cycle assessment (LCA). This paper examines three different types of sustainable concrete mixes, viz., alkali-activated concrete (AAC) with natural coarse aggregates, AAC with recycled coarse aggregates (RCA), and bacterial concrete (BC). A detailed environmental impact assessment of AAC with natural coarse aggregates, AAC with RCA, and BC is performed through a cradle-to-gate LCA using openLCA v.1.10.3 and compared versus PC concrete (PCC) of equivalent strength. The results show that transportation and sodium silicate in AAC mixes and PC in BC mixes contribute the most to the environmental impact. The global warming potential (GWP) of PCC is 1.4–2 times higher than other mixes. Bacterial concrete without nutrients had the lowest environmental impact of all the evaluated mixes on all damage categories, both at the midpoint (except GWP) and endpoint assessment levels. AAC and BC mixes are more expensive than PCC by 98.8–159.1% and 21.8–54.3%, respectively.

Investigation of Mechanical Properties of Silk and Epoxy Composite Materials

This research Investigates the new composite materials are fabricated of two or more materials raised. The fibers material from the sources of natural recycled materials provides certain benefits above synthetic strengthening material given that very less cost, equivalent strength, less density, and the slightest discarded difficulties. In the current experiments, silk and fiber-reinforced epoxy composite material is fabricated and the mechanical properties for the composite materials are assessed. New composite materials samples with the dissimilar fiber weight ratio were made utilizing the compression Molding processes with the pressure of 150 pa at a temperature of 80 °C. All samples were exposed to the mechanical test like a tensile test, impact loading, flexural hardness, and microscopy. The performing results are the maximum stress is 33.4MPa, elastic modulus for the new composite material is 1380 MPa, and hardness value is 20.64 Hv for the material resistance to scratch, SEM analysis of the microstructure of new composite materials with different angles of layers that are more strength use in industrial applications.

Co-ground mineral/microfibrillated cellulose composite materials: Recycled fibers, engineered minerals, and new product forms

When pulp and minerals are co-processed in suspension, the mineral acts as a grinding aid, allowing cost-effective production of mineral/microfibrillated cellulose (MFC) composite materials. This processing uses robust milling equipment and is practiced at industrial scale. The resulting products can be used in many applications, including as wet- and dry-strength aids in paper and board production. Previously, we have reported that use of these MFC composite materials in fiber-based applications allow generally improved wet and dry mechanical properties with concomitant opportunities for cost savings, property improvements, or grade developments. Mineral/MFC composites made with recycled pulp feedstocks were shown to offer at least equivalent strength aid performance to composites made using virgin fibers. Selection of mineral and fiber allows preparation of mineral/MFC composites with a range of properties. For example, the viscosity of such formulations was shown to be controlled by the shape factor of the mineral chosen, effective barrier formulations were prepared, and mineral/MFC composites with graphite as the mineral were prepared. High-solids mineral/MFC composites were prepared at 75% total solids (37% fibril solids). When resuspended and used for papermaking, these high-solids products gave equivalent performance to never-dried controls.

Experimental Study on Equivalent Strength of Induced Joints with consideration to Influence of Concrete Strength, Inducer Spacing, and Concrete Age

To prevent the occurrence of temperature cracking, the induced joints of dams are typically arranged to reduce the tensile strength and orderly guide the crack to form at an induced joint, which can protect the dam structure. The state of the joint surface and the equivalent strength and arrangement of the induced joints have important practical significance for preventing the disorderly cracking of the dam. In this study, the concrete strength, inducer spacing, and concrete age were considered as variable conditions to perform axial tension tests on roller compacted concrete (RCC) bidirectional induced joints. A finite element software was used for numerical simulation, and the simulation results were compared with the experimental results. The equivalent strength of the RCC induced joints increased with the spacing of the induced joints, but the rate of increase gradually declined. The equivalent strength of the RCC induced joints rapidly increased in the early stage, but the strength weakening degree was different at different concrete ages. The strength weakening degree of the induced joint section decreased as the concrete strength increased. These results provide a reference for the setting of induced joints in practical engineering.

The use of hollow sphere pigments as strength additives in paper and paperboard coatings—Part 2: Optimization in paperboard formulations for opacity and strength

This report aims to summarize the efforts in testing the properties of coatings for paperboard utilizing hollow sphere pigments (HSPs). HSPs are known to effectively scatter light and replace titanium dioxide (TiO2) in architectural coating formulations. The effect of the particle size and void fraction was evaluated, along with many coating parameters, including level of addition, binder chemistry, and blends of two HSPs. The small HSPs that have optimized voids for scattering light showed equivalent strength to the TiO2-containing control. The strength data was surprising, particularly the improvement in strength for coatings containing large particle size HSPs. Because of this increase in strength, four parts of binder could be removed, which allowed for higher brightness while not compromising other properties, including hot melt glueability. These trends held true using different binder chemistries (styrene acrylic, vinyl acrylic, and styrene butadiene). Upon refining the formulations further, blends of two HSPs showed further benefit.