Next Article in Journal
Effect of Silane Coupling Agent on Tribological Properties of Hemp Fiber-Reinforced Plant-Derived Polyamide 1010 Biomass Composites
Next Article in Special Issue
Anisotropic Failure Strength of Shale with Increasing Confinement: Behaviors, Factors and Mechanism
Previous Article in Journal
Metamaterial Waveguide Devices for Integrated Optics
Previous Article in Special Issue
Grafting Modification of the Reactive Core-Shell Particles to Enhance the Toughening Ability of Polylactide
Open AccessArticle

Compression Fracture of CFRP Laminates Containing Stress Intensifications

Institute of Polymer and Composites, Hamburg University of Technology (TUHH), Denickestrasse 15, D-21073 Hamburg, Germany
CompriseTec GmbH, Steinhöft 5, D-20459 Hamburg, Germany
Institute of Vehicle System Technology, Karlsruhe Institute of Technology (KIT), Rintheimer Querallee 2, D-76131 Karlsruhe, Germany
Author to whom correspondence should be addressed.
Materials 2017, 10(9), 1039;
Received: 30 June 2017 / Revised: 25 August 2017 / Accepted: 31 August 2017 / Published: 5 September 2017
(This article belongs to the Special Issue The Brittle Failure of Different Materials)
For brittle fracture behaviour of carbon fibre reinforced plastics (CFRP) under compression, several approaches exist, which describe different mechanisms during failure, especially at stress intensifications. The failure process is not only initiated by the buckling fibres, but a shear driven fibre compressive failure beneficiaries or initiates the formation of fibres into a kink-band. Starting from this kink-band further damage can be detected, which leads to the final failure. The subject of this work is an experimental investigation on the influence of ply thickness and stacking sequence in quasi-isotropic CFRP laminates containing stress intensifications under compression loading. Different effects that influence the compression failure and the role the stacking sequence has on damage development and the resulting compressive strength are identified and discussed. The influence of stress intensifications is investigated in detail at a hole in open hole compression (OHC) tests. A proposed interrupted test approach allows identifying the mechanisms of damage initiation and propagation from the free edge of the hole by causing a distinct damage state and examine it at a precise instant of time during fracture process. Compression after impact (CAI) tests are executed in order to compare the OHC results to a different type of stress intensifications. Unnotched compression tests are carried out for comparison as a reference. With this approach, a more detailed description of the failure mechanisms during the sudden compression failure of CFRP is achieved. By microscopic examination of single plies from various specimens, the different effects that influence the compression failure are identified. First damage of fibres occurs always in 0°-ply. Fibre shear failure leads to local microbuckling and the formation and growth of a kink-band as final failure mechanisms. The formation of a kink-band and finally steady state kinking is shifted to higher compressive strains with decreasing ply thickness. Final failure mode in laminates with stress intensification depends on ply thickness. In thick or inner plies, damage initiates as shear failure and fibre buckling into the drilled hole. The kink-band orientation angle is changing with increasing strain. In outer or thin plies shear failure of single fibres is observed as first damage and the kink-band orientation angle is constant until final failure. Decreasing ply thickness increases the unnotched compressive strength. When stress intensifications are present, the position of the 0°-layer is critical for stability under compression and is thus more important than the ply thickness. Central 0°-layers show best results for OHC and CAI strength due to higher bending stiffness and better supporting effect of the adjacent layers. View Full-Text
Keywords: stacking sequence; scaling; free-edge; open-hole; compression after impact (CAI); fractography; scanning electron microscopy (SEM); kink-band stacking sequence; scaling; free-edge; open-hole; compression after impact (CAI); fractography; scanning electron microscopy (SEM); kink-band
Show Figures

Figure 1

MDPI and ACS Style

Leopold, C.; Schütt, M.; Liebig, W.V.; Philipkowski, T.; Kürten, J.; Schulte, K.; Fiedler, B. Compression Fracture of CFRP Laminates Containing Stress Intensifications. Materials 2017, 10, 1039.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

Back to TopTop