Numerical and experimental investigation of out-of-plane fiber waviness on the mechanical properties of composite materials

M Thor,M G R Sause,M Nagler,F Maier,U Mandel,R M Hinterhölzl,J Tauchner

doi:10.1007/s12289-020-01540-5

Abstract

The limited capability to predict material failure in composite materials and specifically in wavy composite layers has led to high margins of safety for the design of composite structures. Thus, the full lightweight potential of this class of materials is left unused. To understand the complex failure behavior of composite materials containing out-of-plane fiber waviness under compressive and tensile loading, a non-linear 2D material model was implemented in ABAQUS and validated with extensive experimental test data from compression and tensile tests. Each test was recorded by a stereo camera system for digital image correlation to resolve damage initiation and propagation in detail. This study has shown excellent agreement of numerical simulations with experimental data. In a virtual testing approach various parameters, i.e. amplitude, wavelength and laminate thickness, have been studied. It was found that the failure mode changed from delamination to kink shear band formation with increasing laminate thickness. The wavelength has shown minor influences compared to amplitude and laminate thickness.

Highlights

Fiber-reinforced composite materials allow for a significant reduction in weight due to the comparably low density (c.f. 4–5 times less than steel) and, in addition, fibers can be aligned in accordance with to the load paths
The compression properties were assumed to be more affected by fiber waviness compared to tensile loading [43, 44], results from mechanical tests on wave 1 show a drop of 70% in tensile strength for first ply failure, where mode I delamination occur due to positive stresses in thickness direction σz (Fig. 13c)
The understanding of intrinsic material behavior of fiber reinforced composite materials on microscopic level up to macroscopic or structural level is of crucial importance for the development of suitable material laws for numerical modeling and for a deeper understanding of deformation and damage mechanisms

Summary

Introduction

Fiber-reinforced composite materials allow for a significant reduction in weight due to the comparably low density (c.f. 4–5 times less than steel) and, in addition, fibers can be aligned in accordance with to the load paths This possibility of alignment allows to place the fibers exactly at the position where they are needed to provide the component with its needed stiffness and strength. The placement of the fibers or semi-finished textile products is still often carried out by hand, especially in the aviation industry This allows diverse draping of the unidirectional (UD) layers, woven textiles or non-crimped fabrics (NCF) into the production tool. The increased demand for composite parts for the aviation and automotive industries requires a transition to (partially) automated manufacturing processes Those systems come with a higher deposition rate and ensure reproducible quality, and imply production effects, e.g

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