Prediction of tensile strength of fused deposition modeling (FDM) printed PLA using classic laminate theory

The application of Fused Deposition Modeling (FDM) is restricted due to limited information about the mechanical properties of printed parts. Therefore, it is required to determine the mechanical properties of the FDM properties to avail the full benefit of the FDM process. In the present study, Classic Laminate Theory (CLT) has been employed at the different configurations of layer thickness and raster width. The required elastic constant of material for CLT has been experimentally obtained through FDM printed Polylactic Acid (PLA) unidirectional specimens at 0°, 45° and 90° for different combinations of layer height and raster width. For these different combinations of layer height and raster width, constitutive models were developed to predict the tensile properties of the PLA parts. Tensile strength of the FDM printed bi-directional specimens has been experimentally obtained to validate the proposed CLT model results. The experimental tensile strength data is in good agreement with the data predicted by the proposed CLT model. Higher tensile strength and modulus were achieved with 0° raster angle compared to 90° raster angle. In the case of a bi-directional printed specimen, higher tensile strength was obtained with 45°/-45° raster angle followed by 30°/-60° and 0°/90° raster angle.

Theoretical Analysis of Structural I-beams Using Various Types of Transparent Wood

In this article, a numerical analysis of various types of I-beam with web from transparent wood was performed and compared with standard OSB board and glass web. Properties of transparent plywood which have not yet been produced from new kinds of transparent wood samples were calculated using laminate theory. Results of analysis show, that the transparent wood composites prove to be very promising structural material for future use within the load-bearing structures of buildings. The best properties showed the transparent wood composites infiltrated by cellulose nanofibers (CNF) and polyvinyl alcohol (PVA).

Design and Analysis of a Laminated Composite Tube

Piping is an important material for fluid transportation in modern industry, and well-structured piping can reduce losses due to maintenance and replacement downtime. Therefore it is necessary to design and analyze the pipes in order to optimize their structure. This paper focuses on composite laminated pipes. In this design case, the structural analysis of this pipe will be carried out by applying the laminate theory, and the structural analysis model will be established by using Mathcad software. The stress and strain of each laminate will be calculated by entering the winding angle and the corresponding equations in this software. The final optimal winding Angle can be determined by verifying the winding angles that can be maintained under maximum stress failure criteria using Mathcad contours and detailed tables of winding and torsion angles.

INDUCTION HEATING OF CF/PEKK LAMINATES USING HOMOGENIZATION TECHNIQUES

The primary heat generation mechanisms of carbon fiber reinforced thermoplastic laminates during induction heating are joule losses, junction heating with contact resistance and dielectric hysteresis. In relation, these mechanisms are highly affected by the laminate’s architecture and the anisotropic properties of each ply. A finite element model of the Joule heating process is studied to compare modeling the electrical and thermal properties of each individual ply with a laminate theory homogenization of the thermal and electrical properties. Three different homogenization techniques are compared, and limitations of the approaches are discussed. Experimental induction heating of CF/PEKK panels analogous to the finite element model is performed and quantitative (infrared camera) temperature measurements are compared to the finite element simulations

A Decommissioned Wind Blade as a Second-Life Construction Material for a Transmission Pole

This paper demonstrates the concept of adaptive repurposing of a portion of a decommissioned Clipper C96 wind turbine blade as a pole in a power transmission line application. The current research program is aimed at creating a path towards sustainable repurposing of wind turbine blades after they are removed from service. The present work includes modelling and analysis of expected load cases as prescribed in ASCE 74 and NESC using simplified boundary conditions for tangent pole applications. Load cases involving extreme wind, concurrent ice and wind, extreme ice, differential ice, broken conductor, and broken shield have been analyzed and governing load cases for bending, shear, and torsion have been examined. Relative stiffnesses of different parts forming the wind blade’s cross section (i.e., shell, web, and spar cap) are determined. The corresponding stresses associated with each part under the governing loads are compared to allowable strength values which are determined from composite laminate theory and modelling of the known laminate structure of the E-Glass FRP material. Stresses and deflections obtained are compared with governing reliability-based design criteria and code requirements. The results of the structural analysis indicate that the wind blade can resist the expected loads with reasonable safety factors and that the expected deflections are within permissible limits. Recommendations are provided for detailing and modification of the wind blade for a power pole application in which crossarm and davit connections are highlighted, and foundation details are emphasized.

A CLT based constitutive model to predict distortions and residual stresses in semi-crystalline thermoplastic composites

This paper describes a classical laminate theory-based constitutive model for portraying thermoplastic composites’ mechanical properties and the development of residual stresses during consolidation. The extended Hillier model is applied to describe the material’s crystallisation and as such is able to provide final part quality as a function of the process cooling history while taking into account the first and second crystallisation mechanisms occurring concurrently. With the developed model, a parametric study was performed taking into account layups that are commonly used in the aerospace industry, where general design guidelines are suggested. Some of the advantages of using cross-ply and quasi-isotropic laminates became clear as no shear residual stresses were predicted for those laminates. However, highly anysotropic laminates may also offer structural advantages. Numerical simulations indicate that the crystallisation residual strains can be, although smaller than thermal residual strains, relevant to final part quality. The combination of both effects may result in high residual stresses at ply level which in turn can compromise the ultimate strength of the laminates and make it difficult to attain the desired part’s geometrical tolerances.

Residual stresses developed in thermoplastic composites during laser-assisted tape laying

The main focus of the study is the determination of residual stresses developed in thermoplastic composites during tape placement. An experimental characterization of the residual stresses is carried out and based on the measurement of the curvature variation with temperature for unsymmetrical laminates. The tested plates are made of APC-2 and processed on the SPIDE-TP, a filament winding machine based in Cetim, France. A thermo-mechanical model based on the modified laminate theory is used in this work. Heat transfer and crystallization are taken into account in the model, allowing the description of the evolution of the mechanical properties of the composite during the whole process. The model is able to predict the residual stresses present at the end of the process. The results showed stress gradients through the thickness of the laminates where the transverse residual stresses can reach up to 20 MPa. In addition, the results showed that increasing the mandrel temperature reduces the crystallization and thermal gradients in the laminate thickness.

Anticipating the induced delamination formation in composite laminates subjected to bending loads

In this research, the effects of induced delamination on the variation of the mechanical properties of composite laminates subjected to bending loads are investigated using a micromechanical model. For this purpose, the variation of the mechanical properties of delaminated laminates is determined using stress analysis of damaged ply and classical laminate theory (CLT) relationships. Using the proposed model and CLT, the fracture toughness due to induced delamination formation is presented in cross-ply laminates. Subsequently, the variation of strain energy release rate (SERR) is calculated in terms of crack density using analytical and finite element models to detect dominant failure modes in different crack densities. The results are compared with those of matrix cracking propagation. The results obtained by the proposed analytical model are in good agreement with those obtained by existing numerical and experimental approaches. The proposed model can be utilized to predict induced delamination formation in composite laminates subjected to bending loads.