Effect of Material Anisotropy and Curing Stresses on Interface Delamination Propagation Characteristics in Multiply Laminated FRP Composites

2005 ◽  
Vol 128 (3) ◽  
pp. 383-392 ◽  
Author(s):  
Brajabandhu Pradhan ◽  
Saroja Kanta Panda
Keyword(s):  
Energy Release ◽  
Composite Structures ◽  
Material Anisotropy ◽  
Interlaminar Stresses ◽  
Release Rates ◽  
Frp Composites ◽  
Energy Release Rates ◽  
The Individual ◽  
Delamination Front ◽  
Delamination Propagation

The present study encompasses the thermoelastic effect of material anisotropy and curing stresses on interlaminar embedded elliptical delamination fracture characteristics in multiply laminated fiber-reinforced polymeric (FRP) composites. Two sets of full three-dimensional finite element analyses have been performed to calculate the displacements and interlaminar stresses along the delaminated interface responsible for the delamination onset and propagation. Modified crack closure integral methods based on the concepts of linear elastic fracture mechanics have been followed to evaluate the individual modes of strain energy release rates along the delamination front. It is shown that the individual modes of energy release rates vary along the delamination front depending on the ply sequence, orientation, and thermoelastic material anisotropy of the constituting laminae. This causes the anisotropic and non-self similar delamination propagation along the interface. The asymmetric and nonuniform variations in the nature of energy release rate plots obtained in a thermomechanical loading environment are significant when curing stress effects are included in the numerical analysis and hence should be taken into account in the designs of laminated FRP composite structures.

Research of Underfill Delamination in Flip Chip by the J-Integral Method

2004 ◽  
Vol 126 (1) ◽  
pp. 94-99 ◽  
Author(s):  
Bulu Xu ◽  
Xia Cai ◽  
Weidong Huang ◽  
Zhaonian Cheng
Keyword(s):  
Energy Release ◽  
Thermal Cycle ◽  
Flip Chip ◽  
Electronic Packages ◽  
J Integral ◽  
Release Rates ◽  
Energy Release Rates ◽  
Cycle Loading ◽  
Scanning Acoustic Microscope ◽  
Delamination Propagation

Fracture mechanics approaches have been used to study reliability problems in electronic packages, in particular, adhesion related failure in flip chip assembly. It was verified in this work that the J-integral with a special flat rectangular contour near the crack tip can be used as energy release rate at the interface between chip and underfill. Meanwhile, the delamination propagation rates at the interface was measured by using C-mode scanning acoustic microscope (C-SAM) inspection for two types of flip chip packages under thermal cycle loading. Finally, the half-empirical Paris equation, which can be used as a design base of delamination reliability in flip chip package, has been determined from the crack propagation rates measured and the energy release rates simulated.

scholarly journals Delamination Behaviour of Embedded Polymeric Sensor and Actuator Carrier Layers in Epoxy Based CFRP Laminates—A Study of Energy Release Rates

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3926
Author(s):  
Andreas Hornig ◽  
Anja Winkler ◽  
Eric Bauerfeind ◽  
Maik Gude ◽  
Niels Modler
Keyword(s):  
Mechanical Properties ◽  
Carbon Fibre ◽  
Energy Release ◽  
Composite Structures ◽  
Critical Conditions ◽  
Fibre Reinforcement ◽  
Release Rates ◽  
Composite Layers ◽  
Energy Release Rates ◽  
The Impact

Fiber reinforced composites combine low density with high specific mechanical properties and thus became indispensable for today’s lightweight applications. In particular, carbon fibre reinforced plastic (CFRP) is broadly used for aerospace components. However, damage and failure behaviour, especially for complex fibre reinforcement set-ups and under impact loading conditions, are still not fully understood yet. Therefore, relatively large margins of safety are currently used for designing high-performance materials and structures. Technologies to functionalise the materials enabling the monitoring of the structures and thus avoiding critical conditions are considered to be key to overcoming these drawbacks. For this, sensors and actuators are bonded to the surface of the composite structures or are integrated into the composite lay-up. In case of integration, the impact on the mechanical properties of the composite materials needs to be understood in detail. Additional elements may disturb the composite structure, impeding the direct connection of the composite layers and implying the risk of reducing the interlaminar integrity by means of a lower delamination resistance. In the presented study, the possibility of adjusting the interface between the integrated actuator and sensor layers to the composite layers is investigated. Different polymer layer combinations integrated into carbon fibre reinforced composite layups are compared with respect to their interlaminar critical energy release rates GIc and GIIc. A standard aerospace unidirectionally reinforced (UD) CFRP prepreg material was used as reference material configuration. The investigations show that it is possible to enhance the mechanical properties, especially the interlaminar energy release rate by using multilayered sensor–actuator layers with Polyimide (PI) outer layers and layers with low shear stiffness in between.

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