Investigation of Interlaminar Defects and their Influence on Interlaminar Strength

In this paper, we directed our attention to the interlaminar defects and their influence on the interlaminar strengths. With the aid of a S-570 scanning electron microscope, the morphology and distribution of interlaminar defects were inspected and documented. According to their shape, size and cause of formation, the defects were classified into five types: flakiness void, irregular shaped debond, local imperfectly cured resin, debond in two multi-directional plies, and inhomogeneous fibers and the large scale debond by these fibers. The cause of defects formation was discussed by analyzing the manufacturing process of composites. The influence of defects on the interlaminar strength and its mechanism was analyzed experimentally and theoretically. The results indicate that these defects, with different effects, decrease the interlaminar strength because they form interlaminar cracks, and the interlaminar shear strength is less affected than interlaminar tensile strength, which is measured according to GB4944 test method. To comprehend defects distribution effect, a four-point-bending test method was introduced to measure the interlaminar peel strength, and a discussion was made on the correlation between the interlaminar tensile strength, interlaminar peel strength and in-plane transverse tensile strength. Finally the concept of interlaminar defect coefficient, which can be used to characterize the defects, was set up and the formula to calculate it was proposed.

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Experimental reexamination of transverse tensile strength for IM7/8552 tape-laminate composites

Journal of Composite Materials ◽

10.1177/0021998320914065 ◽

2020 ◽

Vol 54 (23) ◽

pp. 3297-3312

Author(s):

Caitlin M Arndt ◽

Nelson V de Carvalho ◽

Michael W Czabaj

Keyword(s):

Tensile Strength ◽

Weak Link ◽

Surface Preparation ◽

Test Method ◽

Transverse Fracture ◽

Laminate Composites ◽

Transverse Tensile ◽

Specimen Volume ◽

Transverse Tensile Strength

Due to the observed dependence of transverse-tensile strength, Y T, on test geometry and specimen size, there is no consensus regarding a test method that can uniquely measure Y T. This study reexamines the characterization of Y T by comparing results from established flexure tests with results from a new tensile test that exhibits consistent failure in the gage region. Additionally, the effects of surface preparation and direction of transverse fracture are investigated. Results show that Y T is inversely proportional to specimen volume and surface roughness and is insensitive to direction of transverse fracture. The relationship between specimen volume and Y T is adequately captured by Weibull strength-scaling theory, except at the tails of the Y T distributions. However, specimens exhibited microcracking prior to failure, which violates the “weak-link” assumption of the Weibull theory. These findings highlight the challenges of using deterministic Y T values in progressive damage analysis.

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Transverse stresses and modes of failure in tree branches and other beams

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2009.2093 ◽

2009 ◽

Vol 277 (1685) ◽

pp. 1253-1258 ◽

Cited By ~ 30

Author(s):

A. R. Ennos ◽

A. van Casteren

Keyword(s):

Tensile Strength ◽

Fracture Behaviour ◽

Bending Moment ◽

Transverse Tensile ◽

Modes Of Failure ◽

Reinforced Composite ◽

Transverse Tensile Strength ◽

Set Up ◽

Transverse Stresses ◽

Greenstick Fracture

The longitudinal stresses in beams subjected to bending also set up transverse stresses within them; they compress the cross section when the beam's curvature is being increased and stretch it when its curvature is being reduced. Analysis shows that transverse stresses rise to a maximum at the neutral axis and increase with both the bending moment applied and the curvature of the beam. These stresses can qualitatively explain the fracture behaviour of tree branches. Curved ‘hazard beams’ that are being straightened split down the middle because of the low transverse tensile strength of wood. By contrast, straight branches of light wood buckle when they are bent because of its low transverse compressive strength. Branches of denser wood break, but the low transverse tensile strength diverts the crack longitudinally when the fracture has only run half-way across the beam, to produce their characteristic ‘greenstick fracture’. The bones of young mammals and uniaxially reinforced composite beams may also be prone to greenstick fracture because of their lower transverse tensile strength.

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On the Longitudinal and Transverse Tensile Strength and Work of Fracture of a Continuous Fiber Metal Matrix Composite Subjected to Thermal Exposure

Testing Technology of Metal Matrix Composites ◽

10.1520/stp25968s ◽

2009 ◽

pp. 409-409-23

Author(s):

T Kyono ◽

IW Hall ◽

M Taya

Keyword(s):

Tensile Strength ◽

Metal Matrix Composite ◽

Matrix Composite ◽

Metal Matrix ◽

Thermal Exposure ◽

Continuous Fiber ◽

Transverse Tensile ◽

Fiber Metal ◽

Transverse Tensile Strength ◽

Work Of Fracture

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Study on the Creep Properties of Resin Concrete

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.472.649 ◽

2014 ◽

Vol 472 ◽

pp. 649-653

Author(s):

Hui Cun Shen ◽

Kui Tian ◽

Yan Hua Hu

Keyword(s):

Dynamic Stiffness ◽

Structure Design ◽

Test Method ◽

Bending Test ◽

Creep Properties ◽

Four Point Bending ◽

Long Term Effect ◽

Urgent Task ◽

Machined Parts ◽

New Material

Resin concrete is a new material which can be made into machine bed instead of the traditional pieces of gray cast iron as the machine base, it can improve the dynamic stiffness of machine tools and the quality of machined parts, and extend the campaign life, reduce noise and improve efficiency. However, due to the long-term effect of load of the resin concrete, the elastic deformation occurs in its component, and the strain will increase over time. Thus it can affect the resin concretes service life, and the calculation of creep has become an urgent task in structure design and use, which should be taken seriously. In this paper, the bending creep properties of resin concrete beam were studied and analyzed by using four-point bending test method. The creep curve under different load levels were obtained, and the viscoelastic properties were analyzed.

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Sensitivity Analysis of Semi-Circular Bending Test using Plackett–Burman Matrix

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120907587 ◽

2020 ◽

Vol 2674 (2) ◽

pp. 302-312

Author(s):

Shadi Saadeh ◽

Yazan Al-Zubi ◽

Enad Mahmoud ◽

David Renteria ◽

Louay Mohammad

Keyword(s):

Test Method ◽

Bending Test ◽

Test Results ◽

Notch Depth ◽

Air Voids ◽

Scb Test ◽

Negative Effect ◽

American Society ◽

Set Up ◽

Positive Effect

The semi-circular bending (SCB) test is a recently developed test method, adopted by the American Society of Testing and Material (ASTM) as ASTM D8044, to evaluate the cracking resistance of asphalt mixtures. To measure the robustness of the SCB test, a ruggedness test is needed. In this study, the effect of small changes in the key parameters of the test method on the results of the test were numerically investigated. The test method has many variables and set up conditions. Examining all of these parameters would be cumbersome using traditional testing and statistical techniques, as they require a significantly high number of samples. The Plackett–Burman (PB) technique was used to conduct the ruggedness test while reducing the number of tests required. Seven parameters have been examined: notch location, notch depth (low, intermediate and high), air voids, loading rate, and span length. Even using the PB technique, 16 scenarios need to be tested, and each scenario requires three specimens, one for each of the three notch depths. Hence the process requires plenty of time and material. In this study, the SCB test was modeled using a discrete element method (DEM) approach to analyze the fracture behavior of the samples. DEM was used to develop a model that reduced the time and materials required for the SCB test. Results showed that the parameters with most positive effect were intermediate notch depth and notch location, while those with the most negative effect were loading rates and air voids.

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