Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This project investigates the use of Rapid Prototyping (RP), with specific focus on Three Dimensional Printing (3DP), in the manufacture of complex shaped advanced composite parts, using variants of the Resin Transfer Moulding (RTM) method of composite manufacture. This study developed design guidelines, cost models and a process chain by studying data obtained by making example parts, from literature and consultation with industry. Advanced composite materials offer some of the best low weight and high specific strength properties for the solution of design problems. A major disadvantage of these processes, however, is the low production rates possible and the need of costly moulds. The 3DP technologies combined with the RTM composite process was found to enable a lowering of costs and increase in productivity if smaller batch sizes are considered. The most meaningful area of application for RP techniques seems to be for smaller and more complex components. The geometrical freedom allowed by RP technologies allowed the manufacture of parts which are challenging to manufacture by conventional technology such as CNC machining. Example part case studies were completed for a simple part utilising the one sided mould Resin Infusion RTM variant as well as for a complex part utilising the closed mould Vacuum Assisted Resin Transfer Moulding (VARTM) process variant. During these two case studies it was clear that proper part infusion with resin is critical for the manufacture of good quality composite parts free of voids and dry spots. It is possible to improve the resin infusion by correct placement of resin inlet and outlet ports as well as resin channels incorporated in the mould. Correct placement of these features for the case studies was obtained through simulations done with RTM-Worx software. Results also indicated that another useful application of RP technology to RTM is the manufacture of disposable cores for parts with thick cross sections. Resin channels were included on the surface of these cores to improve the mould filling with resin and consequently part quality. An early cost estimation model, based on the work of Veldsman (1995), was developed for the combined RP and RTM manufacturing process. This model may help designers to eliminate expensive design features and enables a quick cost comparison with competing processes. Drawbacks of applying RP techniques to RTM include the limited lifetime of moulds produced with 3DP and the size and accuracy limitations of the RP t echnology. / AFRIKAANSE OPSOMMING: Hierdie projek handel oor die toepassing van die drie-dimensionele druk metode van Snel-Prototipering (Rapid Prototyping) op die vervaardiging van komplekse gevorderde saamgestelde materiaal komponente met die Hars-Inspuit Giet (Resin Transfer Moulding) metode. Die projek behels die opstel van ontwerpsriglyne, koste-modelle en ’n proses-ketting deur data te bestudeer wat bekom is deur middel van die vervaardiging van eksperimentele parte, literatuurstudie asook raadpleging met individue in die industrie. Gevorderde saamgestelde materiale verskaf van die beste sterk, dog ligte oplossings vir sekere ontwerpsprobleme. ’n Ernstige nadeel van hierdie materiale is egter die stadige produksietempo moontlik en die vereiste van duur gietstukke. Die Snel- Prototipering metodes, gekombineerd met ’n saamgestelde materiaal vervaardigingsproses, maak laer kostes met beter produktiwiteit moontlik indien ontwerpers die part grootte- en akkuraatheidsbeperkings in ag neem. Die mees betekenisvolle area van toepassing blyk kleiner en meer komplekse komponente te wees. Die vryheid in geometrie wat moontlik gemaak word deur die Snel- Prototipering tegnologie laat die vervaardiging toe van parte wat uitdagend is om te vervaardig met konvensionele tegnologie soos CNC masjinering. ’n Gevallestudie is voltooi vir ’n eenvoudige part vervaardig met die enkelkant gietstuk vakuum-infusie weergawe van die Hars-Inspuit Giet metode asook vir ’n komplekse part wat vervaardig is met die geslote gietstuk Vakuum Hars-Inspuit Giet weergawe van die basiese metode. Dit het tydens die twee gevallestudies duidelik geword dat deeglike hars infusie van kritieke belang is vir die vervaardiging van goeie kwaliteit parte sonder enige droë kolle of lugruimtes. Dit is moontlik om die hars infusie te verbeter deur hars inlate en uitlate asook hars kanale in die korrekte posisies te plaas. Die korrekte posisies vir hierdie komponente is verkry deur middel van ’n reeks simulasies met die RTM-Worx sagteware. Resultate dui ook daarop dat Snel-Prototipering tegnologie handig te pas kom by die vervaardiging van verbruikbare kerne vir saamgestelde materiaal parte met groter diktes. Hars kanale kan maklik op die kerne se oppervlak geskep word om die hars verspreiding en gevolglik part kwaliteit te verbeter. ’n Vroeë kostevoorspellings model, gebaseer op werk voltooi deur Veldsman (1995), is saamgestel vir die gekombineerde Snel-Prototipering en Hars-Inspuit Giet proses. Hierdie model kan gebruik word om duur ontwerpsbesonderhede op parte te elimineer en om ’n vinnige koste vergelyking met ander vervaardigingsprosesse te toon. Nadele van die toepassing van Snel-Prototipering tegnieke op Hars-Inspuit Giet sluit die beperkte gietstuk-leeftyd en beperkte akkuraatheid in.

<p>  </p> <p>Globally, communities are embracing the cured-in-place-pipe (CIPP) process due to the need to address damaged buried water and sewer pipes. CIPP involves the chemical manufacture of a new plastic pipe inside an existing buried water and sewer pipe, without the need for excavation. The process is popular because it can be 80% less costly than alternative methods and construction workers can be present for hours to not days to weeks. However, as CIPP use has grown, so have the number of hazardous material (HAZMAT) incidents caused by using this practice. Evacuations of daycare centers, schools, homes, healthcare, institutional, and other buildings have been caused. In some cases, chemical exposure victims have required medical assistance and hospital admission. For decades, organizations within the CIPP industry and municipalities have encouraged chemical waste discharge into ambient air, resulting in preventable exposures. Recent work has indicated tons of volatile organic compounds (VOC) may be released during a single CIPP project into the air. Chemicals released include hazardous air pollutants (HAP), carcinogens (CAR), endocrine disrupting chemicals (EDR), and other compounds with little toxicological information. While polymer composites have been manufactured for other applications for more than 50 years, little information exists about what chemicals and materials are used to manufacture CIPPs. As CIPP use has grown along with the number of bystander chemical exposures, concerns about the type, magnitude, and toxicity of chemical emissions from CIPP projects have markedly increased. To reduce the potential for human harm and environmental degradation, a better understanding of CIPP composite chemistry and manufacturing is needed. This dissertation aimed to elucidate the processes that control the composition of waste generated during plastic CIPP manufacture and ascertain how to modify the manufacturing practice to minimize impacts on composite integrity and emission toxicity. </p> <p>Chapter 1 focused on indoor VOC exposure simulation and styrene contamination/ decontamination to evaluate the risk of occupant exposure during CIPP installation. Styrene is a common monomer used in many CIPP resins and can be discharged into the air at CIPP worksites. A review of prior incidents revealed that CIPP waste (liquid, organic chemicals, etc.) could enter nearby buildings through multiple routes including windows, doors, or heating, ventilation, and air conditioning outdoor air intakes. When CIPP is manufactured inside a sanitary sewer pipe, waste can enter buildings through sewer laterals of nearby buildings and through foundation cracks. Study results showed that plumbing seal backflows in bathrooms caused by sewer repair work are hydraulically possible: the minimum pressure required to displace water in the plumbing trap was estimated to be 0.995 kPa and 8.85 kPa for a sink and toilet, separately. These pressures are much lower than those applied by the contractor during the sewer lining (up to 193.05 kPa). Based on the indoor exposure events, the dissipation potential of vapors, as well as the hydraulic calculations, indoor air chemical contamination and decontamination profiles were also examined. A mass balance model of chemical vapor dispersion was developed. Modeling results revealed that bathroom exhaust fan operation during a CIPP project can increase the indoor styrene concentration by enhancing the inflow of styrene-containing air from the sink and toilet. However, the styrene concentration decreased as air leaked across the bathroom door due to reduced suction in the plumbing. Based on incident reviews, chemical magnitudes, and modeling results it was concluded that CIPP waste discharge should be treated as hazardous material discharge, because of its threat to human health. Actions are needed to reduce waste generation and contain the waste, so it does not leave the worksite. Chapter 2 aimed to determine the manufacturing conditions that most influence chemical residual left in the thermally manufactured CIPP. Bench-scale testing of multiple styrene- and non-styrene composites revealed the manufacturing conditions (curing time, temperature, initiator loading) necessary to produce a high integrity composite while minimizing chemical residual and air emissions. Even though the VOC loading of the non-styrene resin (4 wt.%) was much less than that of styrene resin (39 wt.%), the non-styrene resin did contain HAP, EDR, CAR compounds including ethylbenzene, 2-ethylhexanoic acid, methacrylic acid, styrene, toluene, and <em>m</em>-xylene. Study results also revealed that by changing initiator loading a drastic reduction in the amount of styrene (-42 wt.%) and styrene oxide (-33 wt.%) residual left in the newly manufactured composite was achieved. Discoveries prompted a new hypothesis that this decreased residual also prompted a decreased amount of VOCs emitted into the air. The explanation is that this occurs because that a greater amount of the monomer styrene was incorporated into the resin during polymerization and not permitted to enter the air. Despite decades of polymer composite use, this study provides a new fundamental understanding of composite chemicals and techniques for reducing air pollutant emissions during plastic composite manufacture. In Chapter 3, the complexity of organic vapor chemicals found in the air during thermal heating of CIPP composites was explored and quantified. The emission rate of a popular monomer, styrene, was quantified from the materials before, during, and after composite manufacture. Scaling up bench-scale results, 1.9 to 14 US tons and 0.18 to 1.35 US tons of VOCs (0.05 to 0.36 US tons and 0.001 to 0.007 US tons of styrene) were estimated to be emitted during curing of styrene- and non-styrene CIPPs (i.e., typically 1-3 m of diameter pipes). By modifying standard air sampling methods, previously undetectable chemicals associated with CIPP manufacture were found in the styrene-laden air. These include acetophenone, benzaldehyde, phenol, and 1,3,5-trimethylbenzene. Results have immediate relevance to improved air monitoring for public and worker safety. Further, results can be used to examine the cumulative health and environmental risks of the CIPP pollutant mixtures. Chapter 4 focused on identifying CIPP technology/knowledge gaps and feedback from health officials from multiple state and federal agencies. Through this study, a public health workgroup was assembled to include disciplinary experts and 13 federal, state, and city health agencies and public health associations. Building on dialogue with U.S. health officials, the state of knowledge pertaining to CIPP chemical exposures, mitigation, and response actions was reviewed. Topics included 1) CIPP manufacturing process and waste; 2) sewers and buildings; 3) chemical exposure and health; 4) chemical risk assessment; 5) risk communication. This study helped establish relationships among federal, state, and city officials to improve public health response. Additionally, a primer for CIPP chemical fate and transport, as well as assisting in identifying and prioritizing public health information needs was developed. Identification and prioritization of current public health knowledge gaps and proposed practices for reducing exposures to the public and workers were reported. CIPP-related bench and research results throughout the dissertation can serve as an important basis for environmental policy and public health guidelines on the prevention and mitigation aspects of environmental and human health impacts resulting from CIPP manufacturing practices.</p>