Characterization of mixed-mode I/II fracture properties of adhesively bonded yellow-poplar by a dual actuator test frame instrument

Holzforschung ◽  
2012 ◽  
Vol 66 (5) ◽  
pp. 623-631 ◽  
Author(s):  
Edoardo Nicoli ◽  
David A. Dillard ◽  
Charles E. Frazier ◽  
Audrey Zink-Sharp
Keyword(s):  
Layer Thickness ◽  
Mixed Mode ◽  
Fracture Behavior ◽  
Adhesive Layer ◽  
Mode I ◽  
Pure Mode ◽  
Adhesively Bonded ◽  
Yellow Poplar ◽  
Material Systems ◽  
Test Frame

Abstract Experimental results for the fracture behavior under mixed-mode in-plane loading conditions of adhesively bonded wood specimens are reported. The material systems considered involved yellow-poplar (Liriodendron tulipifera), a hardwood of the Magnoliaceae family, as adherends bonded with two different adhesives, a moisture-cure polyurethane (PU) and a phenol/resorcinol/formaldehyde (PRF) resin. A dual actuator test frame permitted fine scanning of fracture behavior over a full range of mixed-mode I/II levels for double cantilever beam (DCB) geometry specimens. These tests showed that, in the considered material systems, the critical strain energy release rate, c, tends to increase as the mode-mixity of the loading increases. In particular, the increase is steeper in proximity to pure mode II loading for the PRF bonded specimens. The experimental values of c obtained were fairly scattered, as is common when testing wood systems. This variability is due in part to the natural variability of wood but also to other factors such as the orientation of the grain in the bonded beams and variations of bondline thickness. In particular, measurements of adhesive layer thickness were performed. This analysis was implemented with microscopic examination of samples cut from untested DCB specimens, where the bondline had not been disrupted by the test. Although the wood parts were power planed prior to bonding, rather large variations of the adhesive layer thickness were observed: on the order of 1–100 μm for specimens bonded with the PU resin and 10–50 μm for specimens bonded with the PRF resin, which showed somewhat more consistent fracture behavior.

A New Idea of Pure Mode-I Fracture Test of Bonded Bi-Materials

2010 ◽  
Author(s):  
Zhenyu Ouyang ◽  
Gefu Ji ◽  
Guoqiang Li ◽  
Su-Seng Pang ◽  
Samuel Ibekwe
Keyword(s):  
Mixed Mode ◽  
Dissimilar Materials ◽  
Test Method ◽  
Interface Fracture ◽  
Mode I ◽  
Mixed Mode Fracture ◽  
Pure Mode ◽  
Fracture Test ◽  
Engineering Structures ◽  
Material Systems

Bi-material systems in which two dissimilar materials are adhesively joined by a thin adhesive interlayer have been widely used in a variety of modern industries and engineering structures. There are two fundamental issues that need to be adequately addressed: (1) Fracture of bonded bi-materials is mixed mode: Mode-I (pure peel) and Mode-II (pure shear). Fracture test implementation of bi-material systems with the traditional Mode-I methods will induce a noticeable mixed mode fracture due to the disrupted symmetry by the bi-material configuration; (2) The popular cohesive zone models (CZMs) for accurate fracture simulations require more than a single parameter (toughness) as is the case in the traditional linear elastic fracture mechanics (LEFM). Thus, J-integral is highly preferred. It can not only capture more accurate toughness value by considering the root rotation effect, but also facilitate the experimental characterizations of the interfacial cohesive laws, which naturally include all required parameters by CZMs. Motivated by these two important issues, a novel idea is proposed in the present work to realize and characterize the pure Mode-I nonlinear interface fracture between bonded dissimilar materials: Despite the approximation with the elementary beam theories, the accuracy is validated by numerical simulations. The proposed approach may be considered as a promising candidate for the future standard Mode-I test method of adhesively bonded dissimilar materials due to its obvious simplicity and accuracy.

Mixed-Mode I/II fracture behavior of asymmetric adhesively-bonded pultruded composite joints

2014 ◽  
Vol 115 ◽  
pp. 43-59 ◽  
Author(s):  
Moslem Shahverdi ◽  
Anastasios P. Vassilopoulos ◽  
Thomas Keller
Keyword(s):  
Mixed Mode ◽  
Fracture Behavior ◽  
Mode I ◽  
Composite Joints ◽  
Adhesively Bonded

Effect of Crack Length on Mixed-Mode Cohesive Fracture of the Adhesively Bonded Joints

2013 ◽  
Vol 748 ◽  
pp. 231-234
Author(s):  
Reza Bakhtiari ◽  
Ehsan Darabi ◽  
Ali Ravaee
Keyword(s):  
Mixed Mode ◽  
Fracture Behavior ◽  
Test Method ◽  
Mixed Mode Fracture ◽  
Pure Mode ◽  
Bonded Joints ◽  
Loading Conditions ◽  
Adhesively Bonded ◽  
Cohesive Fracture ◽  
Adhesively Bonded Joints

In this paper, the mixed-mode cohesive fracture behavior of adhesively bonded joints was investigated based on numerical analysis. A modified version of Arcan specimen was employed to conduct a mixed-mode fracture test using a special loading device. A full range of mixed-mode loading conditions including pure mode-I and pure mode-II loading were created by ABAQUS software. This test method is a simple procedure, clamping/unclamping the specimens is easy to achieve and only one type of specimen is required to generate all loading conditions. Finite element analyses were carried out on specimens with different adherends in order to investigate deeply about cohesive fracture behavior of adhesively bonded joints.

scholarly journals A Direct Method for the Assessment of Cohesive Zone Models for Thin Adhesive Layers Loaded in Mode I, Mode II, and Mixed-Mode I/II

2020 ◽  
Vol 8 (2) ◽  
pp. S1-S31 ◽  
Author(s):  
E. Paroissien ◽  
F. Lachaud ◽  
J. Morlier ◽  
S. Schwartz
Keyword(s):  
Cohesive Zone ◽  
Mixed Mode ◽  
Direct Method ◽  
Mode Interaction ◽  
Mode I ◽  
Mode Ii ◽  
Pure Mode ◽  
Adhesively Bonded ◽  
Cohesive Zone Models ◽  
A Direct Method

In the context of increasing the strength-to-mass ratio of lightweight structures, the adhesively bonded joining technology appears to be an attractive solution. Nevertheless, the adhesive bonding method is important when the structural integrity of joints has to be ensured. In the literature, the cohesive zone models (CZMs) are shown to be able to predict both the static and fatigue strengths of adhesively bonded joints. The strength prediction is dependent on material laws and associated material parameters, characterizing the bondline behaviour mainly under pure mode I, mode II and mixed-mode I/II. The characterization methods are thus crucial. This paper aims at assessing the capabilities to identify the parameters of a particular CZM for both the inverse method, based on the energy balance associated with the path independent J-integral, and of a direct method described in this present work. The particular CZM has a classical shape based on the definition of a bilinear law for each of both pure modes, associated with pure mode interaction energy laws for initiation and propagation under mixed-mode I/II. The methodology used in this paper is based on a numerical test campaign only, involving the macro-element (ME) technique. A new approach for the fast formulation and implementation of ME modelling of two bonded beams is described.

Mixed mode fracture testing of adhesively bonded wood specimens using a dual actuator load frame

Holzforschung ◽  
2010 ◽  
Vol 64 (3) ◽  
Author(s):  
Hitendra K. Singh ◽  
Abhijit Chakraborty ◽  
Charles E. Frazier ◽  
David A. Dillard
Keyword(s):  
Fracture Energy ◽  
Mixed Mode ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Pure Mode ◽  
Mixed Mode Loading ◽  
Mode Mixity ◽  
Adhesively Bonded ◽  
Phase Angles

Abstract An experimental evaluation of mixed mode fracture tests conducted on adhesively bonded wood specimens using a dual actuator load frame is presented. This unit allows the fracture mode mixity to be easily varied during testing of a given specimen, providing improved consistency, accuracy, and ease of testing over a range of loading modes. Double cantilever beam (DCB) type specimens made of southern yellow pine (Pinus spp.) wood substrates bonded with a commercially available one part polyurethane adhesive were tested over a wide range of mode mixities from pure mode I to pure mode II. The critical strain energy release rate (SERR) values were calculated from the measured load, displacement, and crack length data, in combination with material properties and specimen geometric parameters, and compared on a versus fracture envelope plot. Mean quasi-static fracture energy values were calculated to be 390 J m-2 and 420 J m-2 for mode I and mode II fracture, respectively. For various mixed mode phase angles, the critical SERR values were partitioned into mode I and mode II components. In mixed mode loading conditions the cracks were typically driven along the interface, which resulted in lower total fracture energy values when compared with those measured under pure mode I loading conditions. A drop in measured fracture energy of approximately 45% was observed with mode mixity phase angles as small as 16°, implying that engineering designs based on results from the popular mode I DCB test could be nonconservative in some situations. Fracture surfaces obtained at different mode mixities are also discussed. An improved understanding of fracture behavior of adhesively bonded wood joints under mixed mode loading through generation of fracture envelopes could lead to improved designs of bonded wood structures.

Towards pure mode I loading in dissimilar adhesively bonded double cantilever beams

2021 ◽  
Vol 107 ◽  
pp. 102826
Author(s):  
M. Moazzami ◽  
M.R. Ayatollahi ◽  
S. Teixeira de Freitas ◽  
L.F.M. da Silva
Keyword(s):  
Mode I ◽  
Pure Mode ◽  
Cantilever Beams ◽  
Adhesively Bonded ◽  
Mode I Loading ◽  
Double Cantilever Beams

scholarly journals Mixed-Mode Interlaminar Fracture Toughness of Glass and Carbon Fibre Powder Epoxy Composites—For Design of Wind and Tidal Turbine Blades

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2103
Author(s):  
Christophe Floreani ◽  
Colin Robert ◽  
Parvez Alam ◽  
Peter Davies ◽  
Conchúr M. Ó. Brádaigh
Keyword(s):  
Fracture Toughness ◽  
Carbon Fibre ◽  
Composite Structures ◽  
Mixed Mode ◽  
Epoxy Composites ◽  
Mode I ◽  
Mode Ii ◽  
Pure Mode ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture

Powder epoxy composites have several advantages for the processing of large composite structures, including low exotherm, viscosity and material cost, as well as the ability to carry out separate melting and curing operations. This work studies the mode I and mixed-mode toughness, as well as the in-plane mechanical properties of unidirectional stitched glass and carbon fibre reinforced powder epoxy composites. The interlaminar fracture toughness is studied in pure mode I by performing Double Cantilever Beam tests and at 25% mode II, 50% mode II and 75% mode II by performing Mixed Mode Bending testing according to the ASTM D5528-13 test standard. The tensile and compressive properties are comparable to that of standard epoxy composites but both the mode I and mixed-mode toughness are shown to be significantly higher than that of other epoxy composites, even when comparing to toughened epoxies. The mixed-mode critical strain energy release rate as a function of the delamination mode ratio is also provided. This paper highlights the potential for powder epoxy composites in the manufacturing of structures where there is a risk of delamination.

Sign in / Sign up

Export Citation Format

Share Document