Prototyping of petalets for the Phase-II Upgrade of the silicon strip tracking detector of the ATLAS Experiment

In the high luminosity era of the Large Hadron Collider, the HL-LHC, the instantaneous luminosity is expected to reach unprecedented values, resulting in about 200 proton-proton interactions in a typical bunch crossing. To cope with the resultant increase in occupancy, bandwidth and radiation damage, the ATLAS Inner Detector will be replaced by an all-silicon system, the Inner Tracker (ITk). The ITk consists of a silicon pixel and a strip detector and exploits the concept of modularity. Prototyping and testing of various strip detector components has been carried out. This paper presents the developments and results obtained with reduced-size structures equivalent to those foreseen to be used in the forward region of the silicon strip detector. Referred to as petalets, these structures are built around a composite sandwich with embedded cooling pipes and electrical tapes for routing the signals and power. Detector modules built using electronic flex boards and silicon strip sensors are glued on both the front and back side surfaces of the carbon structure. Details are given on the assembly, testing and evaluation of several petalets. Measurement results of both mechanical and electrical quantities are shown. Moreover, an outlook is given for improved prototyping plans for large structures.Comment: 22 pages for submission for Journal of Instrumentatio

Mechanical Behaviour of a Metal-CFRP-Hybrid Structure and Its Components under Quasi-Static and Dynamic Load at Elevated Temperature

Hybrid materials containing a light metal and CFRP are capable to make a relevant contribution in lightweight design and thereby in reducing greenhouse gases causing global warming. An aluminium CFRP-hybrid specimen with a thermoplastic interlayer that is suitable for application for the A-, B-, or C-pillar in a car is investigated in this work regarding the mechanical behaviour due to temperature variation. For this purpose, quasi-static as well as dynamic tensile tests are carried out not only for those hybrid specimens but also for their respective single-material components. Those are supported by various non-destructive testing (NDT) techniques such as thermography and CT-scans of X-ray tomography. The examination of the single materials as well as the hybrid specimens gives us the possibility to understand if a change in the damage process of the hybrid is caused by one of the single materials or the interaction of them. The use of the NDT techniques in combination with the mechanical experiments allows us to obtain a deeper look at the mechanisms causing the respective damage. It stands out that temperature changes affect the damage mechanisms in the hybrid significantly without having great influence on the single materials. In quasistatic testing, the maximum displacement of the hybrid specimens rises at elevated temperature, and in dynamic testing the initial stiffness and the sustained cycles decline significantly. It therefore can be concluded that the interfaces inside the hybrids are affected by temperature changes and play a major role concerning the damage mechanisms. The pure knowledge about the temperature behaviour of single materials is not sufficient for anticipating the behaviour of hybrid specimens under these restrictions

Development Trend of Adhesive Joining of Aluminium Foams

Aluminium foams structures, due to its impact absorbing properties could be considered as passive safety systems in transportations which still have a great potential for development as a way to reduce deaths and injuries, which is also associated to the economic costs and social impacts associated with this problem. On the other hand, from an environmental standpoint, the use of advanced composite materials to this end can also represent an optimized level of energy efficiency. The impact energy absorption, with the use of a well-designed lightweight protection system, is directly related to the thermal efficiency and consumption of the engines, thus leading to a lower level of greenhouse gases sent to the atmosphere. Without developing manufacturing technologies, it can not be possible, that is why the joint technology should adapt to the recent, combinations of materials. The connection between aluminium foam to aluminium foam design is one way for the bonding established by adhesives. In this paper adhesive joining of aluminium foams were investigated for the base of a further research project

Investigation of asymmetrical fiber metal hybrids used as load introduction element for thin-walled CFRP structures

Due to the industrial success of fiber reinforced plastic (FRP) light-weight components, the demand for joining methods suitable for FRP increases as well. Conventional joining elements like rivets and screws or simple clamping are designed for an application in conventional isotropic materials such as steel or aluminum. Therefore, by design these joining elements do not consider characteristic FRP properties such as the orthotropic (fiber) or the setting behavior of matrix materials that are subjected to a constant load. Thus, without any FRP specific adjustments, conventional joining elements will, in most cases, lead to poor results and an inferior joint. Hence, this investigation presents the concept of a layered local metal-hybrid area that can be used as a load introduction element, the "Multilayer-Insert". The design aspects of the hybrid area are discussed for several stacking options. Furthermore, the sensitivity to geometrical design variables and asymmetrical stackings are investigated by a simplified two-dimensional finite element model. The deduced parameter relations are discussed in the context of an application in an automated fiber placement process in order to formulate recommendations for the geometrical parameters

Load-specific variant generation of bead cross sections in sheet metal components by unidirectional carbon fibre reinforcement

Beads are widely used to stiffen sheet metal components subjected to bending loads. Often, these bead-stiffened parts are used in product variants that differ significantly in the amount of acting loads. Lamination of unidirectional carbon fibre reinforced plastic (UD-CFRP) on the top flange area of individual beads represents a method for further increasing weight- specific stiffness: By varying the number of plies, a specifically configured component is obtained for each of the load cases. As a result, no changes to the forming tools are necessary and a minimum amount of the UD-CFRP material is required. In this work, a complete manufacturing process for a fibre reinforced bead was developed: First, a bead cross section geometry with an adapted top flange area to accommodate the UD-CFRP plies was designed and stamped into pre-stretched sheet samples of DX56 steel. Subsequently, the suitability of several surface pre-treatment processes to achieve sufficient bond strength of the composite bead was experimentally investigated and the UD-CFRP plies were applied by lamination. Final bending tests quantified the achievable stiffening effect of the investigated bead variants, showing a significant increase of the maximum supportable load compared to the standard non- reinforced cross-section

Combination of Carbon Fibre Sheet Moulding Compound and Prepreg Compression Moulding in Aerospace Industry

AbstractThe demand for fuel efficient aircraft led to the development of innovative lightweight constructions and the use of lightweight materials, such as carbon fibre reinforced plastics. In the same manner competences in new production technologies have been built up in the aerospace industry. However, current processes for producing lightweight composites with an excellent mechanical performance cause high costs and long process cycles in comparison with approved metal processes. Furthermore the used raw materials, such as carbon fibres and resin, are very expensive. In contrast to these technologies Sheet Moulding Compound is characterised by a very high productivity, excellent part reproducibility, cost efficiency and the possibility to realise parts with complex geometries and integrated functions, e.g. inserts or colouring. The biggest disadvantage of Sheet Moulding Compound parts is a low level of stiffness and strength because of a low fibre-volume fraction, a short fibre length and isotropic fibre distribution. In this context the combination of Sheet Moulding Compound and Prepreg compression moulding in an one-shot compression moulding and curing process merges the advantages of both materials to create load-bearing and autoclave-quality parts without an autoclave. In the following article, this new technology and its potential will be presented. This paper will also deal with the resulting material characteristics

Life Cycle Energy Assesment of Advanced Fiber Reinforced Composite Design and Manufacturing Methodologies

Automotive industry at large is focused on vehicle light-weighting since a 6%-8% increase in fuel efficiency can be achieved with a 10% reduction in vehicle weight [1]. With the growing demand for cost-effective and sustainable light weighting of automobile structures, interest has increased in the application of fiber reinforced plastic (FRP) composites for use in the Body-in-White (BiW), which can account for up to 40% of the total vehicle weight. Traditional FRP composite manufacturing processes like vacuum assisted resin transfer molding, autoclave consolidation or use of automated fiber placement have been successfully used for marine and aerospace applications. However, these processes are not suitable for the automotive industry due to the low production rate, need for highly skilled labor for manufacturing and quality control, and poor joining with traditional structural materials like steel. This necessitates the use of higher throughput outof-autoclave (OOA) processes like high pressure resin transfer molding (HP-RTM), wet compression molding (WCM) or even fiber reinforced thermoplastics (FR-TP) forming. The transition to these OOA processes face two major challenges: a) the time-consuming iterative design and thermal profiling process required for metal tools which increases cost; and b) the lack of a low-cost, scalable, and sustainable multi-material joining pathways that can enable integration of FRP composite parts with traditional metal structures. This is because existing composite joining methods necessitate significant redesign of existing OEM infrastructure, incur high capital costs, and produce weak joints between metal and composite components. iii To address the first challenge, a new paradigm where additive manufacturing of thermoplastic filament reinforced with continuous fiber is used to develop a low-cost and sustainable composite tool, is investigated. Furthermore, additive manufacturing can enable faster tool design turn-around times and allows for designing of complex tool geometries with embedded sensors and conformal cooling channels. This opens greater avenues for process and design optimization and will enable manufacturers to gain a better understanding of the process based on sensor data gathered in real time from the embedded sensors. To address the later challenge, a highly integrated multi-material, FRP-intensive BiW design was developed using unique multi-material transition joints which retain existing OEM joining infrastructure [2]. It incorporates multi-material transition joints where continuous dry fibers are laid through machined looped channels in a metal substrate and additional metal layers are additively manufactured on top of the looped fiber and metal substrate to embed the fibers within the metal and create a strong metal – fiber mechanical interlocking bond. The fibers are then infused with a thermoset matrix that fills out the loops as well, forming a string FRP-metal transition [3]. Thus, the resulting CFRP component with metal tabs can be spot welded to other metal components without piercing, drilling, or punching holes - significantly increasing the mechanical performance of the multi-material joints. To ascertain the advantages of these multi-material designs and the use of state-of-the-art additively manufactured smart tools, their life cycle impact must be investigated and compared with existing technology. The results from the LCA can provide vital understanding of the energy requirements of the new processes methodologies and can help iv quantify the benefits offered by transitioning to this new proposed paradigm of composite design and manufacturing from a sustainability and emission reduction standpoint. To best of the authors knowledge there have been no studies that address the LCA for each of the proposed solutions. Thus, this work, conducts two comparative life cycle analyses on the proposed additively manufactured smart composite tool for OOA processes and for the multi-material designs for automotive structural components. Different scenarios are studied for both the LCAs to consider the existing FRP production processes as well as the production process of traditional materials

Mechanisms for Introduction of Pseudo Ductility in Fiber Reinforced Polymer Composites- A Review

Advanced polymer matrix composites are gaining the market in their way due to their exceptional specific stiffness, specific strength, fatigue, and corrosion resistance in the field of Auto-Tech, Aero-Tech, Biotech, etc. However, the lack of ductility and catastrophic failure has limited their application in these areas. Hence there is a need to explore means and protocols for designing the reduced factor of safety with high-performance toughened composites. To address this problem, a new generation of high-performance composites with pseudo-ductile or ductile behavior is needed. The ongoing High-Performance Ductile Composite Technology (HiPerDuCT) program jointly between the University of Bristol U.K and Imperial College London to address this challenge by developing newer materials. The fiber architectures made under this project gave a more gradual failure rather than catastrophic failure which improves the mechanical properties. This paper mainly focuses on addressing this evolution of pseudo ductility in fiber-reinforced composites. In addition to this, an attempt has been made to newer possible fiber positions in matrix materials for inducing reasonable ductility in composites