Applied Composite Materials最新文献

This work explored a machine learning (ML) algorithm as a fast data reduction method for translaminar fracture energy in composite laminates. The method was validated with translaminar fracture tests on compact tension (CT) specimens on AS4/8552 and IM7/8552 cross-ply lay-ups. Experimental fracture energy and R-curves for both materials were determined using the most common data reduction methods, such as the compliance calibration (CC), the area (AM) and the Irwin relationship (IM). Our new data reduction method uses a surrogate model based on an artificial neural network (ANN) trained with synthetic data generated with the cohesive crack finite element model. Such a surrogate model maps the cohesive properties with the corresponding load–displacement, crack-displacement and energy-displacement curves with interrogation times in the order of 20 ms and relative errors in the load–displacement and crack growth less than 2%. Such performance enabled its encapsulation to approximate the inverse problem to infer the cohesive parameters with the maximum likelihood estimator (MLE) directly from the experimental load–displacement and crack-displacement curves. The results demonstrated the ability of the model to deliver cohesive parameter inference directly from the macroscopic tests carried out at the laboratory level.

Composite structures are extensively used in several industries such as aerospace, automotive, sports, and construction due to their many advantages, including tailorable mechanical properties, high strength-to-weight ratios, and high specific stiffness. However, due to their low interlaminar tensile and shear strength, composites are prone to delaminations, which can degrade the overall mechanical performance of the structure. Through-thickness stitching provides a third-direction reinforcement to enhance the interlaminar tensile and shear strengths. In this study, quasi-isotropic composite test specimens were manufactured with a novel through-thickness robotic chain stitching with different patterns and tested under uniaxial tensile and three-point bend loadings. A design of experiments (DoE) approach was used to investigate the influence of stitch parameters (stitch density, stitch angle, and linear thread density) on the tensile strength, tensile modulus, and flexural strength of stitched composites. Experimental results are then used to develop a statistically informed response surface model (RSM) to find optimal stitching parameters based on a maximum predicted tensile strength, tensile modulus, and flexural strength. This study reveals and discusses the optimum selection of stitch processing parameters to improve the in-plane and out-of-plane mechanical properties.

We report on the development of phenoxy-graphene nano-composite fibres for improving the toughness of thermoset composites. In this paper, a systematic experimental investigation into the underlying mechanisms of graphene nanoplatelets (GNP) reinforcement of phenoxy nanocomposite fibres prepared via melt spinning is provided. The analysis reveals a tangential orientation of GNP in the outer layer of the fibres, while such orientation is absent in the fibre core region. We show that the relative size of the fibre sheath depends on process variables and exhibits a linear relationship with the modulus of GNP obtained via theoretical analysis using simple rule of mixtures. This is because the area ratio (AR) is proportional to the orientation degree of GNP. This indicates that the enhancement of the Young’s modulus of fibres mainly originates from the increased AR of the fibre sheath layer where the orientation of GNP is more regular.

In this study, an in-depth analysis is carried out to simulate the failure mechanism of T700 carbon fiber-reinforced polymer composite (CFRP) joints with a layup sequence of [45/-45/0/90]_3 s when subjected to tensile loading, both experimentally and numerically. We compared the mechanical performance of three different edge-to-bolt diameter ratios (E/d) of bonded, bolted, and hybrid single lap joints subjected to tensile loading. A finite element-based progressive damage method (PDM) along with the bilinear triangular cohesive zone model (BTCZM) is developed to predict the damage evolution and failure mechanism for all joint configurations. By juxtaposing the simulation outcomes and the experimental data, we observed the failure morphology and assessed the bearing capacity of the joint under tensile loading. The comparison results revealed a minor discrepancy of merely 5.5% in terms of joint load capacity between simulations and experiments, which indicates the high accuracy of our model. The strength of the adhesive and mechanical joints increases with E/d from 3 to 5; however, the strength of the hybrid joints decreases. At E/d = 3, hybrid joints performed significantly better than bonded ones, with a remarkable enhancement of 41.53%. However, for E/d ratios of 4 and 5, both simulation results and test data showed that hybrid joints were inferior to bolted joints. The analytical methodology presented in this paper offers a valuable reference for future analysis and design of composite joints.

This paper presents the theoretical investigations on the free and forced vibration behaviours of carbon/glass hybrid composite laminated plates with arbitrary boundary conditions. The unknown allowable displacement functions of the physical middle surface are expressed in terms of standard cosine Fourier series and sinusoidal auxiliary functions to ensure the continuity of the displacement functions and their derivatives at the structural boundaries. Arbitrary boundary conditions are achieved through the introduction of an artificial spring technique. The first shear deformation theory and Lagrange equations are utilized to derive the energy expression, and the eigenvalue equations associated with free and forced vibration are obtained by Rayleigh-Ritz variational operations. Subsequently, these equations are then solved to determine the natural frequency, mode of vibration, and the steady-state displacement response under forced excitation. The new results are compared with those from references and finite element methods to verify the convergence, accuracy and efficiency of the analytical method. The effects of hybrid ratios, stacking sequences, lamination schemes, fibre orientation, boundary conditions and excitation force on the free and forced vibration behaviours of the carbon/glass hybrid composite laminated plates are analyzed in detail.