Failure Strength Of Composites Research Articles

Probability embedded failure prediction of unidirectional composites under biaxial loadings combining machine learning and micromechanical modelling

This study presents a data-driven, probability embedded approach for the failure prediction of IM7/8552 unidirectional carbon fibre reinforced polymer (CFRP) composite materials under biaxial stress states based on micromechanical modelling and artificial neural networks (ANNs). High-fidelity 3D representative volume element (RVE) finite element models were used for the generation of failure points. Fibre failure and the friction between fibres and matrix after fibre/matrix debonding were taken into consideration and implemented as VUMAT subroutines, respectively. Uncertainty quantification was conducted based on a coupled experimental–numerical approach and failure probabilities were inserted into the failure points to generate the database for the training of ANNs. A total of 15 biaxial stress combinations were considered for the generation of datasets. Two strategies were considered for the construction of form-free failure criteria based on the ANNs for regression and classification problems. It is found that for the regression problems, an ANN model with 2 hidden layers and 64 neurons can achieve a mean square error (MSE) of 0.027% and a mean absolute error (MAE) of 0.78%. For the classification problems, an ANN model with 3 hidden layers and 32 neurons, presents an excellent performance in the prediction with a probability of 98.1%. A good agreement was observed between the failure strength of composites under transverse and in-plane shear predicted by these ANNs and failure envelopes theoretically predicted by Tsai–Wu and Hashin failure criteria.

Effects of Fiber Layer on Failure Strength Properties of Adhesive - Joined Natural Fiber Reinforced Composites

This research was concerned with study of fracture strength of adhesive-lap-joined composites. The tensile and peel tests were carried out with specimens manufactured hybrid stacked composites, because the orientation of fiber and the interfacial fracture between the matrix and the reinforcement had influence on failure strength of composites. Bamboo natural fiber layer was located between polyester layers. The objective of this study was to evaluate the effect of fiber orientation on failure strength properties of composites. The test results were presented by load-displacement graph and finite element analysis. As a result, the load-directional orientation and the thinner thickness of bamboo natural fiber layer have a good effect on peel and tensile-shear strength and failure shape of adhesive-joined hybrid stacked composite.

Effect of a machining-induced defect on the tensile strength of a 3D composite material

This paper investigates the effect of finite specimen size upon the tensile failure of a tridirectional carbon-carbon composite along each reinforcement axis. Asymmetry in the position of load-bearing axial yarns across the cross-section is generated randomly by machining. This yields parasitic bending of the specimen, and thereby premature failure of the yarns subjected to the maximum bending stress. However, bending effects become negligible at final failure. Additionally, the composite failure strength σ F is determined from the cross-sectional area of the actually load-bearing axial yarns, using both symmetrical and asymmetrical specimens. Results are in good agreement with previous work, and we show that the variability of σ F is small.

Effect of changes in elastic constants on the strength of composites

Tensor polynomial, maximum stress, and maximum strain criteria are considered in an investigation of the effect of varying elastic constants on the failure strength of composites. By expressing each criterion in the alternative stress or strain space they are made explicitly dependent on elastic constants as well as strength parameters. The significance of this result is highlighted by an example of the variation in failure envelope produced by altering the Poisson's ratio of the composite material. In particular the failure envelopes for a high strength graphite/epoxy resin (SP-286/T300) composite lamina are examined as a function of variations in the material's Poisson's ratio. The limits in the variation of the Poisson's ratio for this composite lamina are identified.