Method of Experimental Research of New Construction of Beams from Glued Wood with Combined Reinforcement

Structures of glued wood have significant advantages in comparison with structures made of metal or reinforced concrete (less mass, better resistance to the action of chemically aggressive environments, high fire resistance, aesthetic attractiveness, eco-friendliness). However, at the same time, scientists are looking for new ways to improve the characteristics of such wood. We also proposed a new construction of combined reinforcement of glued beams in which the steel bar reinforcement of the periodic profile was arranged in the grooves of the compressed zone, and in the stretched zone reinforcement was carried out with the external composite tape made of carbon fiber. This combination increases both rigidity and bearing capacity of the elements that we are testing from glued wood for work on transverse bending. The method of experimental research on the transverse bend of a new construction of glued beam beams with combined reinforcement was developed. The proposed method fully allows us to examine and experimentally investigate the stress-strain state under load of glued beams from combined reinforcement at different stages of their work.

Structures Technology for Component Damage and Failure Prediction

Advanced structural analysis methods, known as progressive damage and failure analysis tools, are being developed to predict initiation and propagation of damage under repeated loading based on capturing individual and interacting damage modes. This work shows the ability of the progressive damage and failure analysis method implemented in CDMat software developed at the University of Texas Arlington Advanced Materials and Structures Lab to predict strength and fatigue failure of an advanced mechanically fastened aerospace structural joint, the common feature test component (CFTC)—representative of flight-critical structural attributes and failure modes—without a priori knowledge of the test result. The CFTC structural features include a composite tape skin, a composite fabric stiffener, and an aluminum rib applying pull-through load through multiple countersunk bolts combined with the axial compression of skin and stiffener. Failure and damage predictions under static and constant-amplitude cyclic loading are compared with tests. Developed by Boeing under the Air Force Research Laboratory Composite Airframe Life Extension Program, the CFTC has been the most complex progressive damage and failure analysis validation article to date.

Multiresponse Parameter Optimization for the Composite Tape Winding Process Based on GRA and RSM

Composite tape winding is an important forming process of composite materials, which can ensure good performance of composite products. Selection and control of key process parameters in the winding process have a great influence on the properties of products, such as void content and residual stress of products. Through experimental analysis, the residual stress and void content of the composite products are not the minimum when the prepreg winding process is carried out by using the empirical process parameters. To solve this multiobjective optimization problem, experiments were conducted using the Box–Behnken design. The multiobjective optimization problem is converted to a single-objective problem using grey relational analysis (GRA). Principal component analysis (PCA) is used to quantify the relative contributions of residual stress and void content. Regression analysis of grey relational grade (GRG) based on the experimental data was used to develop a second-order GRG prediction model. The winding process parameters were optimized with response surface methodology (RSM), and the winding experiments were carried out with these parameters. The experimental results show that the best combination of process parameters yields the best GRG results with better void content and residual stress.