Application of Failure Criteria on Plywood under Bending

In composite materials, the use of failure criteria is necessary to determine the failure forces. Various failure criteria are known, from the simplest ones that compare individual stresses with the corresponding strength, to more complex ones that take into account the sign and direction of the stress, as well as mutual interactions of the acting stresses. This study investigates the application of the maximum stress, Tsai-Hill, Tsai-Wu, Puck, Hoffman and Hashin criteria to beech plywood made from a series of plies of differently oriented beech veneers. Specimens were cut from the manufactured boards at various angles and loaded by bending to failure. The mechanical properties of the beech veneer were also determined. The specimens were modelled using the finite element method with a composite modulus and considering the different failure criteria where the failure forces were calculated and compared with the measured values. It was found that the calculated forces based on all failure criteria were lower than those measured experimentally. The forces determined using the maximum stress criterion showed the best agreement between the calculated and measured forces.

RP-181: Formulation of Standard Quadratic Congruence of Even Composite Modulus modulo an Even Prime Raised to the Power n

The paper presented here, is a standard quadratic congruence of composite modulus, studied rigorously and found the formulation incomplete. It was partially formulated by the earlier mathematicians. The present authors realised that the earlier formulation need a completion and a reformulation of the solutions is done along with two more results. The author considered the problem for reformulation, studied and reformulated the solutions completely. A partial formulation is found in a books of Number Theory by Zuckerman at el. There the formulation is only for an odd positive integer but nothing is said about even positive integer. The authors have provided a complete formulation of the said quadratic congruence and presented here. Keywords: Composite Modulus, Quadratic Congruence, Reformulation.

RP-179: Formulation of Solutions of Standard Bi-Quadratic Congruence Modulo a POSITIVE INTEGER MULTIPLE to nth Power of Four

In this paper, the author has formulated the solutions of the standard bi-quadratic congruence of an even composite modulus modulo a positive integer multiple to nth power of four. First time a formula is established for the solutions. No literature is available for the current congruence. The author analysed the formulation of solutions in two different cases. In the first case of analysis, the congruence has the formulation which gives exactly eight incongruence solutions while in the second case of the analysis, the congruence has a different formulation of solutions and gives thirty-two incongruent solutions. A very simple and easy formulation to find all the solutions is presented here. Formulation is the merit of the paper.

Effect of Ultraviolet Aging on Composition, Structure and Properties of Asphalt

Asphalt aging is a pivotal factor affecting the service performance of asphalt pavement. Previous studies often ignored the influence of ultraviolet radiation on asphalt aging. Coincidentally, there is no standard test method of photooxidation aging that can be applied to guide engineering practice. In this paper, the influence of ultraviolet aging on the composition, structure and properties of asphalt was studied by adopting Bert four-component method, Fourier transform infrared spectroscopy aned dynamic shear rheometer. Bert four-component method elaborates that the content of asphaltene increases and the content of aromatic component decreases after UV aging. Fourier transform infrared spectroscopy indicates that there are obvious peaks of carbonyl and sulfoxide groups after aging, the penetration of asphalt decreases while the softening point and viscosity increase. Moreover, the composite modulus of asphalt increases obviously at low temperature, but has little effect on the composite modulus at high temperature.

Pile-Soil Stress Ratio and Settlement of Composite Foundation Bidirectionally Reinforced by Piles and Geosynthetics under Embankment Load

The settlement calculation of composite foundation bidirectionally reinforced by piles and geosynthetics is always a difficult problem. The key to its accuracy lies in the determination of pile-soil stress ratio. Based on the theory of double parameters of the elastic foundation plate, the horizontal geosynthetics of composite foundation are regarded as the elastic thin plate, and the vertical piles and surrounding soil are regarded as a series of springs with different stiffness. The deflection equation of horizontal geosynthetics considering its bending and pulling action is obtained according to the static equilibrium conditions. The equation is solved by using Bessel function of complex variable, and the corresponding deflection function of horizontal geosynthetics is deduced. Then, the calculation formula of pile-soil stress ratio and settlement of composite foundation is derived by considering the deformation coordination of pile and soil. The results of engineering case analysis show that the theoretical calculation results are in good agreement with the measured values, which indicates that the proposed method is feasible and the calculation accuracy is good. Finally, the influence of composite modulus of horizontal geosynthetics, tensile force of geosynthetics, and pile-soil stiffness ratio on pile-soil stress ratio and settlement is further analyzed. The results show that the pile-soil stress ratio increases with the increase of the composite modulus of the horizontal geosynthetics, the tensile force of geosynthetics, and the pile-soil stiffness ratio, and the settlement decreases with the increase of the composite modulus of the horizontal geosynthetics, the tensile force of geosynthetics, and the pile-soil stiffness ratio. When the flexural stiffness of the horizontal geosynthetics is small, the influence of the tensile action of the geosynthetics on the pile-soil stress ratio and settlement of the composite foundation cannot be ignored.

An Optimized Statistical Model for Predicting Composite Modulus of Elasticity

Composites are the revolutionary materials that were developed for the ease of the technology. Similar to all families of materials, composites are being extensively studied nowadays. One of the composites ‘main studies is the homogenization study to determine composites modulus of elasticity function of multiple variables based on differentiating several inclusions’ geometries, or quantities or orientations. However, homogenization studies require extensive numerical and analytical work. This work uses a statistical optimized tool TSREG (tabu search combined with statistical regression proven to achieve models with the highest R-squared and lowest p-values for each variable in addition to the lowest MAPE (mean absolute percentage error)) to predict a model relating composite modulus of elasticity to inclusions shape (as aspect ratio), volume fraction, and orientation (0-30-60-90°). Experimental data of modulus of elasticity compressed 3D printed ABS plastics cubes of 16 × 16 × 16 mm3 size having one inclusion (as empty spheres or ellipsoids with zero Young’s modulus) were utilized. For the voids, their geometries were varied to cover spherical and elliptical shapes with several aspect ratios (0.2-0.4-0.65-0.75-0.9-1), volume fractions (0-0.1-0.2-0.3-0.35-0.4-0.5-1), and orientations (0-30-60-90°). This model helps researchers to determine the composite modulus of elasticity using one significant and accurate expression without using numerical analysis.