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

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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Energy release rates of degrading composite structures

10.2514/6.2001-1641 ◽

2001 ◽

Author(s):

Levon Minnetyan ◽

Christos Chamis

Keyword(s):

Energy Release ◽

Composite Structures ◽

Release Rates ◽

Energy Release Rates

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

Journal of Engineering Materials and Technology ◽

10.1115/1.2203100 ◽

2005 ◽

Vol 128 (3) ◽

pp. 383-392 ◽

Cited By ~ 14

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.

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Potential Benefits of the New Westinghouse LOCA Mass and Energy Release Methodology: Estimated Reduction in the Initial Ice Mass Required for an Ice Condenser Containment

Volume 3: Thermal Hydraulics; Instrumentation and Controls ◽

10.1115/icone16-48621 ◽

2008 ◽

Author(s):

Richard P. Ofstun ◽

Thomas F. Antolic

Keyword(s):

Energy Release ◽

Steam Generator ◽

Release Rates ◽

Loss Of Coolant Accident ◽

Loss Of Coolant ◽

Energy Release Rates ◽

Potential Benefits ◽

Computer Codes ◽

The Impact ◽

Containment Pressure

Westinghouse has developed a new loss of coolant accident (LOCA) mass and energy (M&E) release methodology using the WCOBRA/TRAC (WC/T) and GOTHIC computer codes. The new method replaces the deterministic post-blowdown steam generator and metal energy release models with a mechanistic calculation that results in significantly lower steam generator and metal energy release rates. As shown in Reference 1, these lower energy release rates result in a significantly lower post-blowdown containment pressure and temperature for the large dry containment design. This paper estimates the impact of the lower calculated post-blowdown energy release rates on the initial ice mass required to be loaded into an ice condenser containment.

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