Design and construction of a carbon fiber gondola for the SPIDER balloon-borne telescope

We introduce the light-weight carbon fiber and aluminum gondola designed for the SPIDER balloon-borne telescope. SPIDER is designed to measure the polarization of the Cosmic Microwave Background radiation with unprecedented sensitivity and control of systematics in search of the imprint of inflation: a period of exponential expansion in the early Universe. The requirements of this balloon-borne instrument put tight constrains on the mass budget of the payload. The SPIDER gondola is designed to house the experiment and guarantee its operational and structural integrity during its balloon-borne flight, while using less than 10% of the total mass of the payload. We present a construction method for the gondola based on carbon fiber reinforced polymer tubes with aluminum inserts and aluminum multi-tube joints. We describe the validation of the model through Finite Element Analysis and mechanical tests.Comment: 16 pages, 11 figures. Presented at SPIE Ground-based and Airborne Telescopes V, June 23, 2014. To be published in Proceedings of SPIE Volume 914

Laser processing of carbon fibre reinforced plastic (CFRP)

Carbon fibre reinforced plastic (CFRP) is extensively used in automotive and aerospace industries with the aim to achieve reduction on emission by reducing weight and consequently fuel usage. Due to high demand and governmental regulations to reduce the environmental impact, the need for re-using CFRP is becoming an interesting area of application with economic benefits to industry. Cutting CFRP to meet large manufacturing demands with fast cutting speeds and high-quality cuts can impose significant problems for conventional cutting methods. High power lasers can provide fast and efficient cutting speed, but if not controlled effectively can cause excessive fibre damage that has significant impact on the mechanical strength. Secondly, the joining technology is one of the major obstacles in composite parts application. Traditional joining techniques such as screwing and riveting damage the fibres, leading to major stresses due to drilled holes. One way to achieve higher degree of material application is to use adhesive bonding between two surfaces. However, a good adhesion between two surfaces is necessary to achieve strong and high resistance bonds. A surface pre-treatment is essential before the adhesive bonding to bring reproducibility a clean, slightly rough, and preferably active surface. One of the approaches is to use laser as a method of cleaning. Currently lasers are only used to clean the surface of virgin material for surface contamination. This thesis presents a research work using a 1.5 kW single mode fibre laser to investigate the effects of process parameters such as cutting speed, multi-pass, stand-off, large diameter aperture, double aperture and trenching on the reduction of fibre damage to under 100 μm. The fibre damage was observed using scanning electron microscope. Thermal cameras were used to observe the temperature throughout the cutting process. Regression analysis was carried out to develop five models for CAD/CAM interface for quick adaptation of the laser cutting process – in addition, contour plots have been developed for analysis of process parameters on the fibre damage. For laser cleaning a novel approach was used that employs a flash pumped Nd:YAG laser to clean the glue remained on separated CFRP parts, previously joined with PU and EP adhesive with the aim to reduce the CFRP waste by limiting the damage fibre and composite material substrate as a whole and for re-joining purposes. A feasibility study was conducted to assess the developed laser cleaning process in removing adhesive residue from internal curvatures of 3D CFRP components.Carbon fibre reinforced plastic (CFRP) is extensively used in automotive and aerospace industries with the aim to achieve reduction on emission by reducing weight and consequently fuel usage. Due to high demand and governmental regulations to reduce the environmental impact, the need for re-using CFRP is becoming an interesting area of application with economic benefits to industry. Cutting CFRP to meet large manufacturing demands with fast cutting speeds and high-quality cuts can impose significant problems for conventional cutting methods. High power lasers can provide fast and efficient cutting speed, but if not controlled effectively can cause excessive fibre damage that has significant impact on the mechanical strength. Secondly, the joining technology is one of the major obstacles in composite parts application. Traditional joining techniques such as screwing and riveting damage the fibres, leading to major stresses due to drilled holes. One way to achieve higher degree of material application is to use adhesive bonding between two surfaces. However, a good adhesion between two surfaces is necessary to achieve strong and high resistance bonds. A surface pre-treatment is essential before the adhesive bonding to bring reproducibility a clean, slightly rough, and preferably active surface. One of the approaches is to use laser as a method of cleaning. Currently lasers are only used to clean the surface of virgin material for surface contamination. This thesis presents a research work using a 1.5 kW single mode fibre laser to investigate the effects of process parameters such as cutting speed, multi-pass, stand-off, large diameter aperture, double aperture and trenching on the reduction of fibre damage to under 100 μm. The fibre damage was observed using scanning electron microscope. Thermal cameras were used to observe the temperature throughout the cutting process. Regression analysis was carried out to develop five models for CAD/CAM interface for quick adaptation of the laser cutting process – in addition, contour plots have been developed for analysis of process parameters on the fibre damage. For laser cleaning a novel approach was used that employs a flash pumped Nd:YAG laser to clean the glue remained on separated CFRP parts, previously joined with PU and EP adhesive with the aim to reduce the CFRP waste by limiting the damage fibre and composite material substrate as a whole and for re-joining purposes. A feasibility study was conducted to assess the developed laser cleaning process in removing adhesive residue from internal curvatures of 3D CFRP components

ANALYSIS OF SURFACE INTEGRITY IN MACHINING OF CFRP UNDER DIFFERENT COOLING CONDITIONS

Carbon Fiber Reinforced Polymers (CFRP) are a class of advanced materials widely used in versatile applications including aerospace and automotive industries due to their exceptional physical and mechanical properties. Owing to the heterogenous nature of the composites, it is often a challenging task to machine them unlike metals. Drilling in particular, the most commonly used process for component assembly is critical especially in the aerospace sector which demands parts of highest quality and surface integrity. Conventionally, all composites are machined under dry conditions. While there are drawbacks related to dry drilling, for example, poor surface roughness, there is a need to develop processes which yield good quality parts. This thesis investigates the machining performance when drilling CFRP under cryogenic, MQL and hybrid (CryoMQL) modes and comparing with dry drilling in terms of the machining forces, delamination, diameter error and surface integrity assessment including surface roughness, hardness and sub-surface damage analysis. Additionally, the effect of varying the feed rate on the machining performance is examined. From the study, it is concluded that drilling using coolant/ lubricant outperforms dry drilling by producing better quality parts. Also, varying the feed rate proved to be advantageous over drilling at constant feed

탄소/에폭시 수리를 위한 복합재 프린터

학위논문(박사)--서울대학교 대학원 :공과대학 기계항공공학부,2020. 2. 안성훈.Carbon-fiber composites are widely used in airplanes, and the development of electric vehicles has spurred demand as interest in light materials has increased concurrently. Thus, researchers have begun to study how users of these products repair them, but the properties of fiber composites make it difficult to measure the level of destruction in repaired areas. The repair process is usually based on hand-lay-up. The success of this method depends on the repairer's proficiency, and it takes much labor and time to cut carbon fibers according to the size and shape of the repair part. Furthermore, the post-curing process also takes a long time, regardless of the size of the repair area. This can lead to a large amount of waste when repairing small components, such as the surfaces of car parts. Another issue is how best to evaluate the repaired area. If monitoring the life cycle or deformation of the component is conducted, even after the repair has been carried it, the user can anticipate and prepare for repairs based on strain sensor data. Studies of large equipment, such as conventional airplanes, and the use of automated tape layering (ATL) to make large carbon composite materials have been actively underway since 2016. However, most previous research has been aimed at producing large carbon-fiber composite materials and reducing the ᅮ waste and labor required for repair processes. However, there are no automated processes for smallscale repairs. Various small devices, from vehicles to mobile phones, use composites and thus require appropriate repair processes. Studies focusing on these issues are still lacking. In this study, we developed a rapid curing carbon-fiber composite printer. This can achieve a uniform fiber composite by automating the fiber laying method. A rapid curing device using Joule heat is used for local repairs. The repair time is reduced by mounting the rapid curing device on the printer. The proposed printing system is validated by comparing the recovery rates of undamaged specimens and double-lap repaired specimens. These repaired samples achieve uniform quality following repeated repair, and are thus superior to conventional hand-lay-up repaired samples. The use of the rapid curing system improved the recovery rate by 93% or more in the double lap test. As mentioned previously, the variables used to describe the repair performance, which may vary depending on the technician's proficiency, are stabilized under our system. The rapid curing is also optimized by mounting a feedback system between the temperature and electric power. This achieves uniform recovery rates, regardless of user proficiency. Non-destructive testing is also possible if we attach highly sensitive nanoparticle sensors to the device. The quality of the repair is assessed based on the life cycle and deformation of adhesive repair patches, which are evaluated using the proposed sensors. In this study, we propose the use of a rapid curing carbon composite printer and nanoparticle sensors. We expect that the composite printer developed in our research can be used to support the development of carbon composite applications in industries such as electric vehicles and airplanes.탄소 섬유 복합재의 수요는 비행기 산업 및 풍력 발전 산업 등에서 많이 사용되어 왔으며, 전기차의 발전으로 인해 경량소재에 대한 관심 또한 증가하면서 더욱 많은 수요가 발생하였다. 이에 따라 이 제품들을 사용하는 사용자들의 수리방법에 대한 연구가 진행되어왔으며, 섬유 복합재의 특성상 수리된 부위의 파괴수준을 측정하기 어렵고, 이를 확인한 후에도 수리과정이 작업자의 손을 이용한 작업이 주된 방법이다. 이 방법은 수리자의 숙련도에 크게 수리의 성능이 좌우되는 방법이며, 수리부위의 크기와 형태에 따라 탄소 섬유를 재단하는데 큰 노동과 시간이 들어간다. 또한 복합재의 다른 특성인 후경화 과정은 수리과정에서 긴 시간을 요구하며, 이는 수리 부위의 크기와 상관없이 긴 시간이 걸리기 때문에 자동차 부분 파손 혹은 휴대폰 외관 수리와 같은 작은 파트를 수리하는 부분에 있어 큰 낭비가 될 수 있다. 수리를 완료한 이후에도 이 수리부의 수명이나 변형을 측정함으로써, 사용자가 파손을 예측하고 대비하고 정도에 따라 수리과정을 준비할 방법 또한 필요하다. 본 연구에서는 위와 같은 문제들에 대하여 사람의 손으로 진행해야 하는 부분을 자동화함으로써 변수를 통합 및 안정화하고, 긴 시간을 차지하는 후경화를 국지적 주울열을 통한 급속 경화 장치를 추가함으로써 급속 경화 탄소 섬유 복합재 프린터를 개발하였다. 기존의 비행기나 대형 탄소복합재를 만들기 위한 Automated tape laying (ATL) 과 같은 대형 장비들에 대한 연구들이 2016 부터 활발히 진행되었으나, 기존 연구의 대부분은 대형 탄소 섬유 복합재를 제작하는 것을 목적으로 진행하고 있어, 후경화의 단축에 대한 연구수행과 소규모성의 수리를 위한 자동화 공정에 대한 연구는 여전히 부족한 실정이다. 또한 본 연구의 국지적 수리에 적합한 주울열을 통한 급속 경화 장치가 적용된 사례는 없다. 이와 같이 본 연구에서 제안된 프린팅 시스템을 이용하여 양면 접착 방식의 수리 시편을 만들어 기존 미파괴 시편과의 파단강도에 따른 비율을 회복률이라고 정의하였다. 또한 실험을 통해 회복률을 확인하였고, 프린팅을 통한 수리 시편은 인장강도 기준으로 80% 이상 수준을 달성하였고 급속 경화 시스템을 추가한 시편의 경우는 짧은 구간에서 더 높은 접착력을 보이면서 93%이상 회복률로 향상되었다. 또한 앞서 제시한 바와 같이 수리자의 숙련도에 따라 변경될 수 있는 수리 성능에 대한 변수를 규격화 하였으며, 온도와 전력량 간의 피드백 시스템을 형성하여 급속 경화 또한 최적화함으로써 사용자의 숙련도와 상관없이 균일한 회복률을 얻을 수 있는 효과를 얻었고 이에 접착 수리 패치의 수명과 대변형과 같은 수리파손 예방을 위한 나노입자 센서를 부착하고 무선통신 시스템을 적용함으로써 비파괴 검사 또한 진행할 수 있도록 하였다. 본 연구에서 제안된 급속 경화 탄소 복합재 프린터와 이를 검사할 수 있는 시스템의 원리를 응용한 기술은 발전될 탄소 섬유를 이용한 전기차 혹은 휴대기기 시장 등 산업적 응용 분야 확장에 기여할 것으로 기대된다.1 CHAPTER 1. INTRODUCTION 1 1.1 OVERVIEW 1 1.2 CARBON FIBER REINFORCED PLASTIC (CFRP) 5 1.3 CFRP REPAIR 5 1.4 THE GOAL OF THIS RESEARCH 7 1.5 OUTLINE OF DISSERTATION 9 2 CHAPTER 2. BACKGROUND 11 2.1 DEMAND FOR CFRP 11 2.2 BONDED PATCH REPAIR 13 2.3 STRUCTURAL HEALTH MONITORING (SHM) 19 3 CHAPTER 3. DESIGN AND FABRICATION 21 3.1 DIRECT CARBON PRINTING SYSTEM 21 3.1.1 Overview of printing system 21 3.1.2 Fiber feeding component 26 3.1.3 Epoxy feeding component 30 3.2 RAPID CURING SYSTEM 32 3.2.1 Overview of rapid curing process 32 3.2.2 Modeling for rapid curing 33 3.2.3 Joule heating module 39 3.2.4 Electric-Thermal feedback module 44 3.3 HIGHLY SENSITIVE SENSOR PATCH FOR SHM 48 3.3.1 Aerodynamically focused nanoparticle (AFN) printing 48 3.3.2 Highly sensitive strain sensor 53 3.3.3 Design of sensor patch and communication system 57 4 CHAPTER 4. EVALUATION 64 4.1 EVALUATION OF PRINTED SAMPLE 64 4.2 EVALUATION OF DEGREE OF CURING VIA RAPID CURING 77 4.3 EVALUATION OF SHM VIA COMMUNICATION SYSTEM 84 5 CHAPTER 5. CONCLUSION 89 BIBLIOGRAPHY 91 요약 (국문초록) 99Docto

Acoustic emission monitoring of wood materials and timber structures: A critical review

The growing interest in timber construction and using more wood for civil engineering applications has given highlighted importance of developing non-destructive evaluation (NDE) methods for structural health monitoring and quality control of wooden construction. This study, critically reviews the acoustic emission (AE) method and its applications in the wood and timber industry. Various other NDE methods for wood monitoring such as infrared spectroscopy, stress wave, guided wave propagation, X-ray computed tomography and thermography are also included. The concept and experimentation of AE are explained, and the impact of wood properties on AE signal velocity and energy attenuation is discussed. The state-of-the-art AE monitoring of wood and timber structures is organized into six applications: (1) wood machining monitoring; (2) wood drying; (3) wood fracture; (4) timber structural health monitoring; (5) termite infestation monitoring; and (6) quality control. For each application, the opportunities that the AE method offers for in-situ monitoring or smart assessment of wood-based materials are discussed, and the challenges and direction for future research are critically outlined. Overall, compared with structural health monitoring of other materials, less attention has been paid to data-driven methods and machine learning applied to AE monitoring of wood and timber. In addition, most studies have focused on extracting simple time-domain features, whereas there is a gap in using sophisticated signal processing and feature engineering techniques. Future research should explore the sensor fusion for monitoring full-scale timber buildings and structures and focus on applying AE to large-size structures containing defects. Moreover, the effectiveness of AE methods used for wood composites and mass timber structures should be further studied

Acoustic emission monitoring of wood materials and timber structures: A critical review

The growing interest in timber construction and using more wood for civil engineering applications has given highlighted importance of developing non-destructive evaluation (NDE) methods for structural health monitoring and quality control of wooden construction. This study, critically reviews the acoustic emission (AE) method and its applications in the wood and timber industry. Various other NDE methods for wood monitoring such as infrared spectroscopy, stress wave, guided wave propagation, X-ray computed tomography and thermography are also included. The concept and experimentation of AE are explained, and the impact of wood properties on AE signal velocity and energy attenuation is discussed. The state-of-the-art AE monitoring of wood and timber structures is organized into six applications: (1) wood machining monitoring; (2) wood drying; (3) wood fracture; (4) timber structural health monitoring; (5) termite infestation monitoring; and (6) quality control. For each application, the opportunities that the AE method offers for in-situ monitoring or smart assessment of wood-based materials are discussed, and the challenges and direction for future research are critically outlined. Overall, compared with structural health monitoring of other materials, less attention has been paid to data-driven methods and machine learning applied to AE monitoring of wood and timber. In addition, most studies have focused on extracting simple time-domain features, whereas there is a gap in using sophisticated signal processing and feature engineering techniques. Future research should explore the sensor fusion for monitoring full-scale timber buildings and structures and focus on applying AE to large-size structures containing defects. Moreover, the effectiveness of AE methods used for wood composites and mass timber structures should be further studied

Formula SAE Monocoque Chassis Development

Formula SAE is a collegiate competition hosted by SAE International with the primary goal being to design, manufacture, and race an open wheel race car. The Cal Poly Racing Formula SAE team strives for improvement every race season and has remained competitive as a result. The 2019-2020 management team determined that further research and development towards the chassis would yield the greatest performance benefit for future seasons, as the previous chassis platform limited packaging and mounting options for vehicle subsystems which interfaced with the chassis. A redesign of the Cal Poly Racing Formula SAE team’s carbon fiber reinforced polymer monocoque chassis was requested to improve subsystem integration, increase torsional stiffness, and reduce weight compared to the previous platform. Specifically, this senior project team focused on manufacturing process improvement and laminate design to meet these goals for the 2020 Formula SAE competition. This report details the design and manufacturing of such a chassis. Specific emphasis was placed on the geometry, laminate, and manufacturing process design. The geometry was designed using subsystem input for satisfactory integration of all subsystem components while maintaining a high specific torsional stiffness. The team also developed numerous analysis tools including spreadsheets and finite element models to design the asymmetric laminate of the chassis. Modular, multi-piece tooling was designed to produce a single-piece chassis and to allow for easy geometric changes in the future. Though two complete chassis were delivered to the Formula SAE team, the outbreak of COVID-19 prevented the collection of data that would have been used to validate the design. However, the Formula SAE team was made aware of the validation plan proposed in this report

Optimization of Picosecond Laser Parameters for Surface Treatment of Composites Using a Design of Experiments (DOE) Approach

Based on guidelines from the Federal Aviation Administration, research supported by the NASA Advanced Composites Project is investigating methods to improve process control for surface preparation and pre-bond surface characterization on aerospace composite structures. The overall goal is to identify high fidelity, rapid, and reproducible surface treatments and surface characterization methods to reduce the uncertainty associated with the bonding process. The desired outcome is a more reliable bonded airframe structure, and to reduce time to achieve certification. In this work, a design of experiments (DoE) approach was conducted to determine optimum laser ablation conditions using a pulsed laser source with a nominal pulse width of 10 picoseconds. The laser power, frequency, scan speed, and number of passes (1 or 2) were varied within the laser system operating boundaries. Aerospace structural carbon fiber reinforced composites (Torayca 3900-2/T800H) were laser treated, then characterized for contamination, and finally bonded for mechanical testing. Pre-bond characterization included water contact angle (WCA) using a handheld device, ablation depth measurement using scanning electron microscopy (SEM), and silicone contamination measurement using laser induced breakdown spectroscopy (LIBS). In order to accommodate the large number of specimens in the DoE, a rapid-screening, double cantilever beam (DCB) test specimen configuration was devised based on modifications to ASTM D5528. Specimens were tested to assess the failure modes observed under the various laser surface treatment parameters. The models obtained from this DoE indicated that results were most sensitive to variation in the average laser power. Excellent bond performance was observed with nearly 100% cohesive failure for a wide range of laser parameters. Below about 200 mW, adhesive failure was observed because contamination was left on the surface. For laser powers greater than about 600 mW, large amounts of fiber were exposed, and the failure mode was predominately fiber tear

Special Issue of the Manufacturing Engineering Society (MES)

This book derives from the Special Issue of the Manufacturing Engineering Society (MES) that was launched as a Special Issue of the journal Materials. The 48 contributions, published in this book, explore the evolution of traditional manufacturing models toward the new requirements of the Manufacturing Industry 4.0 and present cutting-edge advances in the field of Manufacturing Engineering focusing on additive manufacturing and 3D printing, advances and innovations in manufacturing processes, sustainable and green manufacturing, manufacturing systems (machines, equipment and tooling), metrology and quality in manufacturing, Industry 4.0, product lifecycle management (PLM) technologies, and production planning and risks