scholarly journals Resistance of Polymeric Laminates Reinforced with Fabrics against the Growth of Delaminations

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7367
Author(s):  
Piotr Czarnocki
Keyword(s):  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Mode I ◽  
Element Analysis ◽  
Loading Mode ◽  
Hybrid Beam ◽  
The One ◽  
Loading Modes ◽  
Delamination Front

Dependence of the initiation values of the Strain Energy Release Rate, GCi, on the orientation of the reinforcement direction α relative to the delamination front was investigated for two laminates of different interfacial ply arrangements. In the case of the first laminate, the delamination was located at the interface of the layers reinforced with symmetric fabric and unidirectional fabric. In the case of the second laminate, the delamination was located at the interface of layers reinforced with symmetric fabric. In both laminates, the orientation of fibers in the layers separated by the delamination differed by 45° regarding the warp directions. The investigations were carried out for Mode I, Mode II, and Mixed-Mode I/II (GII/GI = 1 and GII/GI = 1.7) loadings using hybrid beam specimens. The major problem appearing in the intended tests was the inevitable lack of symmetry in the xz and xy planes of the specimens and the resulting deformation and stress–strain couplings, causing undesired loading modes. To decrease these couplings, especially designed hybrid beam specimens were used. An auxiliary finite element analysis was performed to assess the remaining effects of the reduced couplings. To ascertain whether statistically significant differences between Gci values for different α occurred, the one-way analysis of variance supplemented by Levene’s test was carried out. The dependence of Gci on α was found out for both laminates. However, it was not equally strong, and it turned out that the loading mode and the interfacial ply were arrangement sensitive.

The Edge Delamination Test: Measuring the Critical Adhesion Energy of Thin-Film Coatings, Part II: Mode Mixity & Application

1994 ◽  
Vol 338 ◽  
Author(s):  
Edward O. Shaffer ◽  
Scott A. Sikorski ◽  
Frederick J. McGarry
Keyword(s):  
Thin Film ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Mode I ◽  
Rigid Substrate ◽  
Edge Delamination

ABSTRACTThe edge delamination test (EDT) is being developed to measure the critical energy required to cause a thin film, under biaxial tensile stress, to debond from a rigid substrate[1]. The test uses circular features etched through biaxially stressed films adhered to a rigid substrate. If the stress is large enough, a stable debond ring grows radially about the feature. We use a finite element analysis to model the test, solving for the applied strain energy release rate as a function of crack length, feature hole radius and other geometrical parameters. The model identifies both mode I and mode II components of the strain energy release rate, and agrees with previous analytical solutions for the total debond energy. However, the model predicts, with a very refined mesh at the crack tip, the fracture process is pure mode I. To explore this result, critical strain energy release rates from the EDT and the island blister test (IBT) are compared. This agreement supports the model prediction that the failure process in the EDT is modeI peeling.

Determination of cohesive laws in wood bonded joints under mode I loading using the DCB test

Holzforschung ◽  
2013 ◽  
Vol 67 (8) ◽  
pp. 913-922 ◽  
Author(s):  
Filipe G.A. Silva ◽  
Jose Xavier ◽  
Fábio A.M. Pereira ◽  
José J.L. Morais ◽  
Nuno Dourado ◽  
...  
Keyword(s):  
Strain Energy ◽  
Inverse Method ◽  
Strain Energy Release Rate ◽  
Direct Method ◽  
Crack Opening ◽  
Strain Energy Release ◽  
Mode I ◽  
Bonded Joints ◽  
Opening Displacement ◽  
Cohesive Laws

Abstract The cohesive laws (CLs) have been investigated by means of direct and inverse methods concerning wood bonded joints under pure mode I. The experimental results were obtained by tests with double cantilever beam. The direct method is based on the differentiation of the relation between strain energy release rate and crack opening displacement at the crack tip. An equivalent crack method was used to evaluate the strain energy release rate in the course of the test without monitoring the crack length, which is difficult to observe exactly. The crack opening displacement was determined by postprocessing local displacements measured by digital image correlation. The inverse method requires a previous assumption of the CL shape, and as such, a trilinear law with bilinear softening relationship was selected. The cohesive parameters were identified by an optimization procedure involving a developed genetic algorithm. The idea is to minimize an objective function that quantifies the difference between the experimental and the numerical load-displacement curves resulting from the application of a given law. A validation procedure was performed based on a numerical analysis with finite elements. Both methods in focus provided good agreement with the experimental data. It was observed that CLs adopted by the inverse method are consistent with the ones obtained with the direct method.

scholarly journals Fracture Behavior of Carbon-Epoxy under Different Loading

2020 ◽  
Vol 9 (3) ◽  
pp. 1145-1149
Keyword(s):  
Fracture Surface ◽  
Strain Energy ◽  
Fracture Behavior ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Mode I ◽  
Mode Ii ◽  
New Materials ◽  
The Common ◽  
Mode Ii Loading

Delamination is the common failures of composite material attributed to various reasons, most importantly the potential stiffness degradation leading to small flaws and subsequently theypropagate, and it becomes essential to characterize the new materials for interlaminar fracture. For the present study Carbon /epoxy system of IM7/8552 was investigated under mode I and mode II loading. Material was formed into unidirectional laminates with Teflon inserts at its mid length. The specimens were machined according to ASTM standards, Tests were executed on a quasi-static Intron 8225, with load control at 5 mm/ min and 2 m/min for the mode -I and mode-II respectively. The strain energy release rate was found to be GIC=0.266 kJ/m2 and GIIC=0.687 kJ/m2 . Fiberbridging was prominently absent in the DCB samples Examination of the fracture surface by SEM at SAIF, in IIT{M) and the nature of the fracture surface revealed the typical failure mechanism pertaining to mode-I and mode-II failuremechanisms

scholarly journals Interlaminar Fatigue Crack Propagation in Mode I of Carbon Fiber/PEEK Composites

1993 ◽  
Vol 2 (1) ◽  
pp. 096369359300200
Author(s):  
G C Christopoulos ◽  
S A Paipetis
Keyword(s):  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Double Cantilever Beam ◽  
Cyclic Strain ◽  
Strain Energy Release ◽  
Mode I ◽  
Interlaminar Fracture Toughness ◽  
Fatigue Cycle ◽  
Delamination Growth ◽  
Thermoplastic Matrix

A study of the mode I interlaminar fracture toughness of a unidirectional carbon fibre reinforced thermoplastic matrix composite has been made using Double Cantilever Beam, DCB, specimens. Delamination growth per fatigue cycle, da/dN, was related with the maximum applied cyclic strain energy release rate, GIMAX, using a power law.

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