On the Relationship between Engineering Properties and Delamination of Composite Materials

1981 ◽  
Vol 15 (4) ◽  
pp. 336-348 ◽  
Author(s):  
Carl T. Herakovich
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Composite Laminates ◽  
Strong Influence ◽  
Mutual Influence ◽  
Engineering Properties ◽  
Moisture Expansion ◽  
Interlaminar Shear Stress ◽  
Interlaminar Shear ◽  
The Relationship

The influence of the coefficient of mutual influence, poisson's ratio and coefficients of thermal and moisture expansion on delamination is studied. Engineering theories are compared to finite element and experimental results. It is shown that the mismatch in coefficient of mutual influence can have a strong influence on delamination with fiber angles in the 10°—15° range being critical for adjacent (±θ) layer combinations. The mismatch in coefficient of mutual influence is reduced by a factor of two and the interlaminar shear stress τzx is reduced significantly when the ±θ layers are interspersed between 0° and 90° layers. It is shown how the results can be used for design of composite laminates.

An Interlaminar Shear Stress Continuity Theory for Both Thin and Thick Composite Laminates

1992 ◽  
Vol 59 (3) ◽  
pp. 502-509 ◽  
Author(s):  
Xianqiang Lu ◽  
Dahsin Liu
Keyword(s):  
Shear Stress ◽  
Composite Laminates ◽  
Present Theory ◽  
Transverse Shear Deformation ◽  
Elasticity Analysis ◽  
Equilibrium Equations ◽  
Composite Interface ◽  
Laminate Theory ◽  
Interlaminar Shear Stress ◽  
Interlaminar Shear

The interlaminar shear stress plays a very important role in the damage of composite laminates. With higher interlaminar shear stress, delamination can easily occur on the composite interface. In order to calculate the interlaminar shear stress, a laminate theory, which accounts for both the interlaminar shear stress continuity and the transverse shear deformation, was presented in this study. Verification of the theory was performed by comparing the present theory with Pagano’s elasticity analysis. It was found that the present theory was able to give excellent results for both stresses and displacements. More importantly, the interlaminar shear stress can be presented directly from the constitutive equations instead of being recovered from the equilibrium equations.

Numerical Analysis of Interlaminar Stress Distributions around Hole in Thermoplastic Laminate

2011 ◽  
Vol 368-373 ◽  
pp. 1543-1546
Author(s):  
Guo Hua Zhao ◽  
Qing Lian Shu ◽  
Bo Sheng Huang
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Stress Concentration ◽  
Numerical Models ◽  
Finite Element Code ◽  
Stress Distributions ◽  
Interlaminar Stress ◽  
Hole Edge ◽  
Interlaminar Shear Stress ◽  
Interlaminar Shear

This paper investigates the interlaminar stress distributions at hole edge of notched thermoplastic laminates. Two numerical models of AS4/PEEK laminates with configuration of [±25]S4 and [0/±45/90]2S were built and studied by finite element code ANSYS. The results show: (1) The angle-ply configuration ([±25]S4) may cause more severe concentration of interlaminar shear stress at hole edge; (2) the quasi-isotropic configuration ([0/±45/90]2S) can lessen the stress concentration at hole edge.

Finite Element Aided Design Evolution of Composite Leaf Spring

2006 ◽  
Vol 3-4 ◽  
pp. 429-434 ◽  
Author(s):  
J. Hou ◽  
George Jeronimidis
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Maximum Shear Stress ◽  
Leaf Spring ◽  
Original Design ◽  
Virtual Production ◽  
Glass Fibre Reinforced ◽  
Spring System ◽  
Interlaminar Shear ◽  
Aided Design

This paper shows the process of the virtual production development of the mechanical connection between the top leaf of a dual composite leaf spring system to a shackle using finite element methods. The commercial FEA package MSC/MARC has been used for the analysis. In the original design the joint was based on a closed eye-end. Full scale testing results showed that this configuration achieved the vertical proof load of 150 kN and 1 million cycles of fatigue load. However, a problem with delamination occurred at the interface between the fibres going around the eye and the main leaf body. To overcome this problem, a second design was tried using transverse bandages of woven glass fibre reinforced tape to wrap the section that is prone to delaminate. In this case, the maximum interlaminar shear stress was reduced by a certain amount but it was still higher than the material’s shear strength. Based on the fact that, even with delamination, the top leaf spring still sustained the maximum static and fatigue loads required, the third design was proposed with an open eye-end, eliminating altogether the interface where the maximum shear stress occurs. The maximum shear stress predicted by FEA is reduced significantly and a safety factor of around 2 has been obtained. Thus, a successful and safe design has been achieved.

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