Search NASA⌕ Search

SEARCH · Search NASA

Results for “Defect”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

In Situ Thermal Inspection of Automated Fiber Placement Operations for Tow and Ply Defect Detection

The advent of Automated Fiber Placement (AFP) systems have aided the rapid manufacturing of composite aerospace structures. One of the challenges that AFP systems pose is the uniformity of the deposited prepreg tape layers, which complicates detection of laps, gaps, overlaps and twists. The current detection method used in industry involves halting fabrication and performing a time consuming, visual inspection of each tape layer. Typical AFP systems use a quartz lamp to heat the base layer to make the surface tacky as it deposits another tape layer. The innovation proposed in this paper is to use the preheated base layer as a through-transmission heat source for inspecting the newly added tape layer in situ using a thermographic camera mounted on to the AFP hardware. Such a system would not only increase manufacturing throughput by reducing inspection times, but it would also aid in process development for new structural designs or material systems by providing data on as-built parts. To this end, a small thermal camera was mounted onto an AFP robotic research platform at NASA, and thermal data was collected during typical and experimental layup operations. The data was post processed to reveal defects such as tow overlap/gap, wrinkling, and peel-up. Defects that would have been impossible to detect visually were also discovered in the data, such as poor/loss of adhesion between plies and the effects of vacuum debulking. This paper will cover the results of our experiments, and the plans for future versions of this inspection system.

Juarez, Peter D.↗
NASA NTRS2023

Leveraging Automated Fiber Placement Computer Aided Process Planning Framework for Defect Validation and Dynamic Layup Strategies

Process planning represents an essential stage of the Automated Fiber Placement (AFP) workflow. It develops useful and efficient machine processes based upon the working material, composite design, and manufacturing resources. The current state of process planning requires a high degree of interaction from the process planner and could greatly benefit from increased automation. Therefore, a list of key steps and functions are created to identify the more difficult and time-consuming phases of process planning. Additionally, a set of metrics must exist by which to evaluate the effectiveness of the manufactured laminate from the machine code created during the Process Planning stage. Layup strategies, in addition to dog ears, stagger shifts, steering constraints, and starting points, represented the group of functions labeled as process optimization and ranked the highest in terms of priority for automation. The laminates resulting from the selected parameters are evaluated through the occurrences of principal defect metrics such as fiber gaps, overlaps, angle deviation and steering violations. This document presents an automated software solution to the layup strategy and starting point selection phase of process planning. A series of ply scenarios are generated with variations of these ply parameters and evaluated according to a set of metrics entered by the Process Planner. These metrics are generated through use of the Analytical Hierarchy Process (AHP), where relative importance between each of the fiber features are defined. The ply scenarios are selected which reduce the overall fiber feature scores based on the defects the Process Planner wishes to minimize.

HiCAM↗
NASA NTRS2022

Latex–collagen membrane: an alternative treatment for tibial bone defects

Due to the difficulty of consolidation, the risk of fractures, and the high cost of therapy, the orthopedic field views the restoration of bony defects or post-traumatic diseases as a significant issue. In recent years, efforts have been made toward guided bone regeneration as a viable solution. In this study, natural rubber latex (NRL) and latex–collagen (NRL-COL) membranes were developed and characterized, and their effects on bone regeneration in rat tibial lesions were assessed. According to the physicochemical findings, the hydrolyzed COL was effectively incorporated into the NRL membrane to produce a more robust membrane (348% increase in stress) and showed good biocompatibility for human dermal fibroblast cells and in hemolytic activity assay. According to bone analysis using computed microtomography, a substantial difference in bone volume (BV) was found among NRL, control (CONT), and NRL-COL. NRL-COL exhibited the greatest value for the bone volume/total volume ratio (BV/TV). The presence of NRL and COL was significant for the analysis of BV and BV/TV, respectively. All the experimental groups demonstrated a higher bone quality and fracture resistance, as shown by the mechanical properties of the bone. In the COL group, both neoformation of bone and total collagen levels were greater, indicating that treated defects had been closed and mature bone cells were present. Due to its angiogenic properties and the low cost of NRL membrane production, the NRL-COL membrane could be a good substitute for upcoming bone regeneration applications.

Marcela Britto de Paiva↗
NASA NTRS1966

Quenched-in defects in Mo-35Re

Feasibility of using quenched-in defect technique to study effect of rhenium on vacancy clustering in Mo-35Re

CRYSTAL STRUCTURE DEFECT↗