OPTIMIZATION OF PROCESS PARAMETERS DURING CO-CURE OF HONEYCOMB SANDWICH STRUCTURES

Honeycomb sandwich structures are co-cured to bond partially cured thermoset prepreg facesheets with an adhesive layer to both sides of the honeycomb core under a pre-defined pressure and temperature cycle in an autoclave. High dependency of the co-cure process on the materials and process parameters makes it susceptible to defect such as poorly consolidated facesheet and highly porous bondline which can cause premature failure of the structure. The temperature and pressure in the autoclave and pressure in the vacuum bag are the parameters that describe the cure cycle of the process. In this work, an optimization of the process cycle for the co-cure process of sandwich structures that maximizes the fiber volume fraction within the prepreg and reduces the porosity is presented. The objective function is constructed to reflect the quality of both the facesheet consolidation and bond-line porosity. The Surrogate Optimization Algorithm is employed to find the cure cycle resulting in the highest facesheet consolidation level and the lowest porosity within the bond-line.

Coronavirus – A Dreaded Lurgy

Who would have thought that oxygen that was so much abundant in atmosphere would become luxury? 2019 witnessed an emergence of a disease named coronavirus, a disease that affected mankind physically, mentally and socially. The coronavirus disease-2019 (COVID-19) pandemic, caused by the new coronavirus SARS-CoV-2, spread around the globe with unprecedented consequences for the health of millions of people. While the pandemic is still in progress, with new incidents being reported every day, the resilience of the global society is constantly being challenged. Health system has been catastrophied by this pandemic. There is shortage of medicine, hospital beds, hospital staff and basic amenities as well. In these tough times people have looked to alternative system of medicine to get rid of this deadly virus. Homeopaths marched forward in treating mild to moderate cases and the after effects of SARS-COV-2 infection on human economy. Effective results have been noticed the cure process. Prevention and management of this highly transmissible respiratory viral illness require a holistic and interprofessional approach that includes physicians' expertise across specialties, nurses, pharmacists, public health experts, and governmental authorities.

Surface Functionalization of Cotton Fabric with Ag3PO4 via Citric Acid Cross-linking Using An Industrialized Padding Process and Its Self-Cleaning Performance

Cotton fabric was first modified with citric acid to introduce surface carboxyl groups, which then coordinated with Ag+ ions to prepare the Ag3PO4 finished cotton fabric through further reacting with PO43- ions using an industrialized pad-dry-cure process. Increasing surface carboxyl groups could significantly enhanced the loaded content of Ag3PO4. The padding process could more strongly fix Ag3PO4 on fabric than the conventional dipping method. The Ag3PO4 finished cotton fabric showed higher photocatalytic capacity than pure Ag3PO4 particles owing to the synergetic effect of the Ag complex with the carboxyl groups on the fabric. Moreover, the treatment of KBr and fixing agent further improved the the stability and anti-photocorrosion performance of the samples. Importantly, the finished fabric also exhibited better self-cleaning performance for Reactive Red 195 as a model stain under varied irradiation. The dye was found to be decomposed and mineralized on the finished fabric under artificial or solar irradiation.

Modeling of Leadframe Strip Warpage after Die Attach Cure Process

In the leadframe package assembly process, silicon die is attached to the leadframe using a die attach adhesive material and the bonded strip is then cured. However, excessive strip warpage after the die attach cure process is a challenging problem that also affects the succeeding assembly processes. In this study, strip warpage modeling was done using a finite element analysis (FEA) technique to understand the warpage mechanism after die attach cure and find options to reduce strip warpage. The effect of changing the leadframe thickness, die thickness, and the leadframe design in terms of the number of strip panels or changing the connecting bar was analyzed. Modeling demonstrated that lead frame contracts faster than the silicon die resulting in the “frowning” warpage that agrees with the actual observation. It was also shown that increasing the die thickness by 25% results in 27% warpage reduction. Results also showed that increasing the number of panels or maps in a strip could significantly reduce the strip warpage. Improving the panel-to-panel isolation using stress relief cuts is also another option to reduce warpage after die attach cure.