Advanced Bio-based Composite Panels for Building Facades

Traditional exterior walls are heavy, offer insufficient insulation, and have poor durability, making it challenging to meet the combined requirements of energy efficiency and structural enclosure performance. To address the issues of excessive weight and inadequate insulation in conventional concrete exterior wall panels, alternative materials and designs are being adopted. A novel double-layer composite wall panel structure is proposed, arranging normal concrete (NC) on the exterior side to ensure the panel’s durability and ceramsite foam concrete (CFC) on the interior side to enhance thermal insulation and reduce thermal bridging effects. To address the scenario where the wall panel is subjected to out-of-plane loads during service, causing stress in the CFC layer, bending performance tests were conducted on CFC-NC double-layer composite panels under load applied on the CFC side. Research shows that CFC-NC double-layer composite wall panels exhibit bending performance under four-point bending conditions that is basically consistent with that of monolithic wall panels. As the thickness of the CFC layer increases, cracks may appear near the interface in the CFC layer that do not extend from NC cracking, and may even occur earlier than NC cracking. As the density grade of CFC decreases, the compressive deformation of CFC becomes more pronounced; however, no crushing of the CFC occurs at the ultimate bearing capacity stage. Under four-point bending conditions, the strain at the mid-span section of the composite wall panel along the thickness direction is basically linearly distributed. Under the same conditions of wall panel thickness, reinforcement ratio, and shear span ratio, the flexural bearing capacity of CFC-NC double-layer composite wall panels with CFC density grades A8, A6, and A4 is approximately 12.5%, 25.03%, and 18.29% lower, respectively, compared to C30 cast-in-place wall panels. The flexural bearing capacity of the composite panels increases correspondingly with the increase in CFC layer thickness and reinforcement ratio. Specimens with smaller shear span ratios exhibit more pronounced shear effects. Based on the stress–strain relationship of CFC, a modified calculation method for the flexural capacity of ordinary concrete sections is presented. Referring to the ACI 318-14 code, a calculation method for the bending deformation of composite wall panels is provided. The research results can offer a theoretical basis for the design and application of CFC-NC double-layer composite wall panels.

Composite Biomarker Panel in Prediction of Severity and Diagnosis of Acute GvHD with T- Depleted Allogeneic Stem Cell Transplants- Single Centre Pilot Study

The non-linear stability analysis of composite cylindrical panel subjected to concentrated in-plane mechanical and localized thermal loadings are reported here. The buckling of composite panel subjected to concentrated in-plane mechanical loading/ localized thermal loading is solved in two steps as the prebuckling stress distribution within the panel is not known a priori. In the first step, the semi-analytical expressions for the pre-buckling stresses within the composite cylindrical panel under in-plane mechanical/ thermal loadings are developed by solving in-plane elasticity/thermoelasticity problem. Subsequently, using these in-plane stresses within the cylindrical panel, the governing equations for nonlinear stability of layered composite panel are formulated using variational principle. The cylindrical panel is modeled based on Donnell’s shallow shell theory considering higher order shear deformation theory and incorporating von-Karman geometric nonlinearity. The Galerkin’s method is used to solve the non-linear governing partial differential equations. The influence of different types of mechanical and thermal loadings, initial geometric imperfections, and radius of curvature on the postbuckling equilibrium paths is investigated.

*† ‡ Prediction of the transmission loss of singly curved sandwich composite panels is presented for a special class of symmetric construction. Measurements of the transmission loss for such a panel are presented and compared to the predictions. Additional results for the panel covered with acoustic absorbing foams are presented and compared to predictions. The foam addition increases the panel apparent damping, and results in a larger increase of transmission loss than can be attributable to the added mass. It is concluded that the model accurately predicts the transmission loss and other acoustic properties. It can be employed for the acoustic design of such panels. Sandwich composite panels and cylinders are extensively employed in the aerospace industry. Their applications are commonly found in aircraft, helicopters, launch vehicles, and engine cowlings. Ironically, the light weight advantage of the composite sandwich construction could lead to higher interior noise levels. The prediction of the sound transmission into such structures requires the analysis of acoustic wave propagation in curved composite sandwich panels. Moreover, control of the interior cavity noise almost always requires the introduction of acoustic treatments such as sound absorbing foam or fiberglass. This paper presents an abridged version of a wave approach analytical treatment for predicting the transmission loss of curved composite sandwich panels. Moreover, a test panel was constructed and employed in a transmission loss test for the bare panel and the panel covered with acoustic foam. Description of the test and representative results for the bare and covered panel are given. The transmission loss prediction for orthotropic and multi-layered infinite cylinders was investigated in a series of papers by Blaise et al. 1-3 They first presented a displacement field which neglected the transverse shear and rotary inertia, and followed it by a more general model referred to as the 3-D model. Modal based finite element and boundary element methods were employed for predictions of sound transmission through a curved honeycomb composite panel, and were verified in transmission loss tests.

Design of composite insulation panels containing 100% recycled cotton fibers and polyethylene/polypropylene packaging wastes

Elaboration of X-ray shielding of highly barite-loaded polyester concrete: structure, mechanical properties, and MCNP simulation

A novel higher-order coupled finite-boundary element scheme is presented for the computation of the thermoacoustic responses of the layered panel structure under the harmonic excitation. The thermally pre-stressed vibrating composite panel model is derived mathematically using the higher-order shear deformation mid-plane kinematics. The eigen frequencies and the corresponding vibrational mode shapes are computed via the finite element method using Hamilton’s principle. Similarly, the surrounding medium is modeled via Helmholtz wave equations and solved numerically using the boundary element steps for the computation of the acoustic responses. The frequency and sound radiation output are computed numerically by means of an own computer code prepared in MATLAB environment. To avoid excess thermal loading during analysis, the critical buckling temperature of the composite panel structure is obtained and the range of thermal loading is selected accordingly. The model accuracy is demonstrated through the proper comparison studies of different structural responses (critical buckling temperature, natural frequency and radiated sound power level) of the curved composite panel with the available benchmark solutions. The reliability and the usefulness of the proposed novel scheme have been revealed by solving several numerical illustrations for different lamination schemes, panel geometries including the geometrical parameters.

Aircraft structures must be capable of performing their function throughout their design life while meeting safety objectives. Such structures may contain defects and/or damages that can occur for several reasons. Therefore, aircraft structures are inspected regularly and repaired if necessary. The concept of combining an inspection plan with knowledge of damage threats, damage growth rates, and residual strength is referred to as “damage-tolerant design” in the field of aircraft design. In the present study, we fabricated a composite panel with a cutout (which is generally found in the bottom skin of the wing) using a resin infusion process and studied the damage tolerance of a co-cured skin-stringer composite panel. The composite panel was subjected to low-velocity impact damage, and the extent of damage was studied based on non-destructive inspection techniques such as ultrasonic inspection. Fixtures were designed and fabricated to load the composite panel under static and fatigue loads. Finally, the panel was tested under tensile and fatigue loads (mini TWIST). Deformations and strains obtained from FE simulations were compared and verified against test data. Results show that the impact damages considered in this study did not alter the load path in the composite panel. Damage did not occur under the application of one block (10% life) of spectrum fatigue loads. The damage tolerance of the stiffened skin composite panel was demonstrated through test and analysis.

This paper presents imaging results from measurements of an industrially manufactured composite test panel, utilizing two introduced algorithms for data postprocessing. The system employs a planar near-field scanning setup for characterizing defects in composite panels in the 50-67-GHz band, and can be considered as a complementary diagnostic tool for nondestructive testing purposes. The introduced algorithms are based on the reconstruction of the illuminating source at the transmitter, enabling a separation of the sampled signal with respect to the location of its potential sources, the scatterers within the device under test or the transmitter. For the second algorithm, an L1-minimization problem formulation is introduced that enables compressive sensing techniques to be adapted for image retrieval. The algorithms are benchmarked against a more conventional imaging technique, based on the Fourier transform, and it is seen that the complete imaging system provides increased dynamic range, improved resolution, and reduced measurement time by removal of a reference measurement. Moreover, the system provides stable image quality over a range of frequencies.

Buckling analysis of piezoelectric cylindrical composite panels reinforced with carbon nanotubes

Aims of research. Polymer unidirectional composite laminate panel behavior with interlaminate defects under action of different dynamic loads is consider. Methods. Normal modes and eigenvalues of rectangular composite panels in the presence multiple delamination different sizes ellipsoidal form are calculated. The dependences of the maximum deflections from the frequency of the stationary pressure field action are constructed. Distribution field of panels plies failure index under action of nonstationary pressure field by using different failure criteria for composites is determined. Results. Modeling methodology composite panels behavior in the presence multiple interlaminar defects under action of different dynamic loads is developed. Analysis of failure panel with the use of different failure criteria for composites is carried out.

Improved longitudinal magnetic shielding by an amorphous FeSi steel composite panel

The effect of in-plane stresses on the stability behaviors of constant stiffness and variable stiffness composite panels, exposed to aerodynamic pressure, is studied using the finite element method. The dynamic pressure from the high velocity airflow is evaluated from the first-order piston theory, and the eigenvalue analysis is performed to investigate the flutter or divergence type of instabilities in such composite panels under combined mechanical and aerodynamic loads. Attempt is made to understand the effect of the lamination parameter on the stability characteristics of edge-supported and cantilever composite trapezoidal panels. Finally, the limit cycle oscillation of variable stiffness plates subjected to aerodynamic pressure is investigated.

Thin walled stiffened composite panels are among the most utilized structural elements in ship structures. The composite layered panels with fibers are the most usually used in shipbuilding, aerospace industry and in engineering constructions as well. These structures possess the unfortunate property of being highly sensitive to geometrical and mechanical imperfections. These panels, unfortunately, have one important characteristic connected to big sensitivity on geometrical imperfections (different dimensions comparative with the design ones). The defects are of following types: different directions of fibers design, variations in thickness, inclusions, delaminations or initial transversal deformations. Ship structure plates are subjected to any combination of in plane, out of plane and shear loads during application. Due to the geometry and general load of the ship hull, buckling is one of the most important failure criteria of these structures. This is why it is necessary to develop the appropriate methodologies able to correctly predict the behavior of a laminated composite plate in the deep postbuckling region, at the collapse load, which is characterized by separation between the skin and the stiffeners, delaminations, crack propagations and matrix failure, as well as to understand its behavior under repeated buckling. During its normal service life, a ship hull, which is composed of many curved laminated composite stringer stiffened panels, may experience a few hundreds of bucklingpostbuckling cycles. Although it is well recognized that CFRP stiffened structures are capable of withstanding very deep post-buckling, yielding collapse loads equal to three four times their buckling load (Bisagni & Cordisco, 2004, Knight & Starnes, 1988), there exists scarce knowledge in the literature about the effects of repeated buckling on the global behavior of the laminated composite panels under combined loading influences. According to the studies, it is possible to predict on how far into the post-buckling region it is possible to increase loading without loosing structural safety. Buckling failure mode of a stiffened plate can further be subdivided into global buckling, local skin buckling and stiffener crippling. Global buckling is collapse of the whole structure, i.e. collapse of the stiffeners and the shell as one unit. Local plate buckling and stiffeners crippling on the other hand are localized failure modes involving local failure of only the skin in the first case and the stiffener in the second case. A grid stiffened panel will fail in any of these failure modes depending on the stiffener configuration, plate thickness, shell winding angle and type of applied load.

Pendry et al. [J. B. Pendry, A. J. Holden, D. J. Robbins, and W. J. Stewart, IEEE Trans. Microwave Theory Tech. 47, 2075 (1999)] and Smith et al. [D. R. Smith, W. J. Padilla, D. C. Vier, S. C. Nemat-Nasser, and S. Schultz, Phys. Rev. Lett. 84, 4184 (2000)] have shown that the effective magnetic permeability, μ, of free space can be rendered negative over a certain frequency range by a periodic arrangement of very thin conductors with suitable magnetic resonance properties, the so-called split-ring resonators. Because of its rather bulky architecture, this structure does not lend itself to a proper integration into a reasonably thin real composite structural panel. To remedy this fundamental barrier, we invented a new magnetic resonator consisting of very thin folded plates that are suitably nested within one another to form folded-doubled resonators (FDRs) that can be integrated into an actual composite panel. Measurements, using a focused beam electromagnetic characterization system combined with time-domain numerical simulations of the reflection and transmission coefficients of such a composite slab have revealed that indeed the composite has a negative μ over a frequency range of about 9.1–9.35 GHz [S. Nemat-Nasser, S. C. Nemat-Nasser, T. A. Plaisted, A. Starr, and A. Vakil Amirkhizi, in Biomimetics: Biologically Inspired Technologies, edited by Y. Bar Cohen (CRC Press, Boca Raton, FL, 2006)]. Thus, it has become possible to construct a structural composite panel with negative index of refraction by simultaneously creating negative effective ε and μ [V. G. Veselago, Sov. Phys. Usp. 10, 509 (1968); R. A. Shelby, D. R. Smith, and S. Schultz, Science 292, 77 (2001); A. F. Starr, P. M. Rye, D. R. Smith, and S. Nemat-Nasser, Phys. Rev. B 70, 113102 (2004)].