Analysis Of The Mechanical Response Of Impact Loaded Composite Sandwich Structures With Focus On Foam Core Shear Failure
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Analysis of the mechanical response of impact loaded composite sandwich structures with focus on foam core shear failure
Author: Tim Berend Block
language: en
Publisher: Logos Verlag Berlin GmbH
Release Date: 2014
Sandwich structures are an economically and structurally efficient way of designing large integral composite parts. In the aerospace industry pre-impregnated face sheets and honeycomb core structures can be considered as industry standard while e.g. naval structures and wind turbine blades typically use vacuum infusion technology with polymer foam cores. Application of the less costly infusion technology in the aeronautical industry requires a thorough understanding of the damage tolerance including low velocity impact as a frequent source of damaging events. At low impact energies damage in composite foam core sandwich structures is limited to core crushing and local face sheet delaminations. Higher impact energies may initiate the competing failure modes face sheet rupture and core shear failure depending on impact, geometric and material parameters. Face sheet rupture leads to severe local damage with typically good visibility, while core shear failure leads to cracks and rear face sheet debonding of the foam core with less visibility. This work investigates the low velocity impact response of sandwich structures with carbon fiber reinforced plastic (CFRP) face sheets and a polymeric foam core using experiments at room temperature and at -55° Celsius. An analytically derived failure mode map is presented as a simple tool for design guidelines while the explicit finite element method is applied for a more detailed description of the sandwich impact process. Both models are used to analyze the impact response and describe relevant sensitivity parameters of sandwich structures.
Analysis of the mechanical performance of pin-reinforced sandwich structures
Author: Mohamed Adli Dimassi
language: en
Publisher: Logos Verlag Berlin GmbH
Release Date: 2019-11-15
The rising demand to reduce fuel consumption and the continuous increase of materials and manufacturing costs has obliged aircraft manufacturers to boost the use of composite materials and to optimise the manufacturing methods. Foam core sandwich structures combine the advantages of high bending properties with low manufacturing costs when liquid composite processes are used. However, the use of foam core sandwich structures is not widespread in aircraft applications due to the better weight-specific performance of honeycomb cores and the susceptibility to impact loading. In this context, pin reinforcements are added to the foam core to improve its mechanical properties and its damage tolerance. This work contributes to the understanding of the mechanical behaviour of pin-reinforced foam core sandwich structures under static and impact loading. Ultrasonic scan and micro-computed tomography are used to identify the different damage modes. The effect of very low temperature on the damage behaviour under impact loading is investigated. An explicit simulation model to predict the impact response of pin-reinforced foam core sandwich structures is also proposed.
A rapid virtual autoclave for carbon fiber reinforced plastics
Author: Junhong Zhu
language: en
Publisher: Logos Verlag Berlin GmbH
Release Date: 2023-01-26
Structural carbon fiber reinforced plastic parts are usually manufactured through autoclave processing for high-performance aerospace applications. Today’s aerospace composite manufacturing techniques require high quality with robust manufacturing processes. Manufacturing process simulation enables the investigations of physical effects and manufacturing process mechanisms. This approach has been increasingly used to predict and optimize the manufacturing process for high part quality at low manufacturing costs. Owing to a complicated manufacturing environment involving multi-physics characteristics, there is a critical need to develop an efficient and cost-effective numerical methodology with a systematic study. This thesis contributes to the systematic investigations of the process modeling, simulation, thermal measurement, and optimization in composite manufacturing of autoclave processing. The method provides a correct and efficient thermal analysis and optimization in autoclave processing to achieve better process control and ensure the quality of composite parts. The presented framework can be applied directly in autoclave production with larger dimensions and full-scale tools for aerospace structures. The developed methodology allows quick delivery guidelines of production plans and optimization strategies for composite manufacturing in a highly useful and cost-effective way, thereby reducing the cost in the design and manufacturing phase. Since July 2017, Mr. Junhong Zhu has been working as a research assistant in the department of modeling and simulation at the FIBRE (Faserinstitut Bremen e.V.) at the University of Bremen. He deals with the process modeling and simulation in composite manufacturing of autoclave processing. His research focuses on numerical methods, such as computational fluid dynamics and finite element methods, muti-physics coupling schemes, and process optimization. He is also interested in the use of artificial intelligence in the manufacturing process.