Analytical Method to Obtain Ply Specific Engineering Constants from Simple Material Tests of NCF Composite Parts

This presentation was made at the 2019 NAFEMS World Congress in Quebec Canada

Resource Abstract

The work presented in this paper introduces a new concept that aims to capture the inaccuracy in the elastic mechanical properties of fibre reinforced plastics (FRPs) related to the underlying heterogeneity and manufacturing defects. This novel approach introduces a new concept that uses the raw surface deformation and load information from simple mechanical tests of laminates with multidirectional lay-up and returns the engineering constants of the layers. It is based on the backward use of the Classical Laminate Theory (CLT) thus, it has been named after it as CLT-1. Based on the stiffness formulation used in CLT, all relevant in-plane engineering constants like moduli and in-plane Poisson’s ratio may be evaluated in one step for every ply. In order to take into account the variations in material properties, the elaborated algorithm has also been equipped with a built-in AI module which enables the system to operate as a “self-learning” algorithm while processing the individual test data. Therefore, the output is a probability distribution for each engineering constant rather than a single value. The relevance of this approach is especially high for Non-Crimped Fabric (NCF) composites as the material of the future “morphing” composite structures.

Conventionally, the ply specific engineering constants are estimated from simple tension, compression, bending and shear tests of unidirectional (UD) laminates. Each constant comes from different test type that always raises a statistical concern about the conformity of the derived parameters. Moreover, the implementation of engineering constants derived from UD tests is always an extrapolation of data when it is applied on multidirectional laminates.

However, when the ply stack-up is selected wisely for the above mentioned simple material tests, the new method returns all stiffness parameters in one go in a vector form. Hence the previously mentioned statistical non-conformity is handled. In addition, the system is easy to use due to its compactness and it surely gives the experimental strains and displacements since the procedure is initiated from the deformation of the target multidirectional laminate.

Document Details

AuthorKovacs. L
Date 18th June 2019
OrganisationeCon Engineering Kft.


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