title: Development of an integrated sacrificial sensor for damage detection and monitoring in composite materials and adhesively bonded joints

authors: Ólafsson, G.

abstract: Quality assurance of adhesively bonded joints is of vital importance if their benefits are to be exploited across a wide range of industrial applications. A novel lightweight, low-cost, non-invasive embedded sacrificial sensor is proposed, capable of detecting damage within an adhesively bonded joint, which could also be used in a laminated composite structure. The sensor operation uses changes in electrical resistance, increasing as the sensing material area diminishes with damage progression. Initial tests prove the sensor concept by showing that the electrical resistance of the sensor increases proportionally with material removal, mimicking the sensor operation. Thermography is used to verify the current flow through the sensor and that any localised heating caused by the sensor is minimal. Short beam interlaminar shear strength tests show that embedding sensors in a composite laminates did not cause a reduction in material interfacial structural performance. Finally, the in-situ performance of the sensor is demonstrated in quasi-static tensile tests to failure of adhesively bonded Single Lap Joints (SLJs) with sensors embedded in the bond line. Prior to crack initiation an electrical response occurs that correlates with increasing applied load, suggesting scope for secondary uses of the sensor for load monitoring and cycle counting. Crack initiation is accompanied by a rapid increase in electrical resistance, providing an indication of failure ahead of crack propagation and an opportunity for timely repair. As the crack damage propagated, the electrical response of the sensor increased proportionally. The effect of the sensor on the overall structural performance was assessed by comparing the failure load of joints with and without the embedded sensor with no measurable difference in ultimate strength. The research presented in the paper serves as an important first step in developing a simple yet promising new technology for structural health monitoring with numerous potential applications.

text: Development of an integrated sacrificial sensor for damage detection and monitoring in composite materials and adhesively bonded joints Quality assurance of adhesively bonded joints is of vital importance if their benefits are to be exploited across a wide range of industrial applications. A novel lightweight, low-cost, non-invasive embedded sacrificial sensor is proposed, capable of detecting damage within an adhesively bonded joint, which could also be used in a laminated composite structure. The sensor operation uses changes in electrical resistance, increasing as the sensing material area diminishes with damage progression. Initial tests prove the sensor concept by showing that the electrical resistance of the sensor increases proportionally with material removal, mimicking the sensor operation. Thermography is used to verify the current flow through the sensor and that any localised heating caused by the sensor is minimal. Short beam interlaminar shear strength tests show that embedding sensors in a composite laminates did not cause a reduction in material interfacial structural performance. Finally, the in-situ performance of the sensor is demonstrated in quasi-static tensile tests to failure of adhesively bonded Single Lap Joints (SLJs) with sensors embedded in the bond line. Prior to crack initiation an electrical response occurs that correlates with increasing applied load, suggesting scope for secondary uses of the sensor for load monitoring and cycle counting. Crack initiation is accompanied by a rapid increase in electrical resistance, providing an indication of failure ahead of crack propagation and an opportunity for timely repair. As the crack damage propagated, the electrical response of the sensor increased proportionally. The effect of the sensor on the overall structural performance was assessed by comparing the failure load of joints with and without the embedded sensor with no measurable difference in ultimate strength. The research presented in the paper serves as an important first step in developing a simple yet promising new technology for structural health monitoring with numerous potential applications.

year: 2021

title: Genetic variability of New Zealand seagrass (Zostera muelleri) assessed at multiple spatial scales

authors: Jones, Tracey C.

subjects: RAPDs

abstract: We conducted RAPD analyses at multiple spatial scales to contribute to the conservation and future restoration of New Zealand's seagrass, Zostera muelleri Irmisch ex Asch. (Zosteraceae). Initially we focused on fine-scale genetic variation within two estuaries on the North Island, one on the East coast the other on the West coast. Within each estuary individuals were genetically similar, however, there was clear genetic separation between the two sites (genetic distance D = 0.2965). Genetic variation within a sampling location (m scale) was similar to that observed among sampling locations (km scale) within a site (21% and 28%, respectively) and smaller than that observed between sites (51%). We then expanded our sampling to include a further six populations distributed across almost the entire latitudinal (ca. 15°) gradient of the North and South Islands. At this scale genetic differences were closely correlated with coastal currents. There was a clear separation between North Island and South Island populations and further separation between the East and West coast populations of each Island. Sites located along the same section of coastline were more genetically similar than those from the opposite coast and other Island. Genetic similarity was highest within each of the sites, indicating a low degree of gene flow between populations. We recommend that any future restoration and conservation projects use only locally eco-sourced materials for population augmentations.

text: Genetic variability of New Zealand seagrass (Zostera muelleri) assessed at multiple spatial scales We conducted RAPD analyses at multiple spatial scales to contribute to the conservation and future restoration of New Zealand's seagrass, Zostera muelleri Irmisch ex Asch. (Zosteraceae). Initially we focused on fine-scale genetic variation within two estuaries on the North Island, one on the East coast the other on the West coast. Within each estuary individuals were genetically similar, however, there was clear genetic separation between the two sites (genetic distance D = 0.2965). Genetic variation within a sampling location (m scale) was similar to that observed among sampling locations (km scale) within a site (21% and 28%, respectively) and smaller than that observed between sites (51%). We then expanded our sampling to include a further six populations distributed across almost the entire latitudinal (ca. 15°) gradient of the North and South Islands. At this scale genetic differences were closely correlated with coastal currents. There was a clear separation between North Island and South Island populations and further separation between the East and West coast populations of each Island. Sites located along the same section of coastline were more genetically similar than those from the opposite coast and other Island. Genetic similarity was highest within each of the sites, indicating a low degree of gene flow between populations. We recommend that any future restoration and conservation projects use only locally eco-sourced materials for population augmentations.

year: 2008

title: Biculturalism in practice, ‘Te Pounamu’: Integration of a Māori model with traditional clinical assessment processes

authors: Manna, Leona

subjects: Maori

abstract: Traditional clinical psychological assessment follows a western paradigm of interaction, which relies heavily on verbalisations of internal and external symptoms. This process relies upon the assumption of and acceptance that tangata whaiora (consumer/s) are able to do this. Training encourages a clinical psychologist to take into account differences which may or may not be obvious, e.g., differences in religious beliefs, gender, hearing, or sight. However, as clinicians we often neglect to assess tangata whaiora abilities to verbalise such information. Te Pounamu, as a Māori model demonstrates the underlying principles of Te Tiriti O Waitangi. Providing the best treatment outcomes is about acknowledging all aspects of one’s wellbeing: physical, mental, spiritual, and whānau. Te Pounamu provides a process that acknowledges such aspects in a way of knowing that is healing. From clinical experience, the interactive mode that Te Pounamu utilises has been found efficacious in assisting tangata whaiora to understand how such factors contribute to poor mental health.

text: Biculturalism in practice, ‘Te Pounamu’: Integration of a Māori model with traditional clinical assessment processes Traditional clinical psychological assessment follows a western paradigm of interaction, which relies heavily on verbalisations of internal and external symptoms. This process relies upon the assumption of and acceptance that tangata whaiora (consumer/s) are able to do this. Training encourages a clinical psychologist to take into account differences which may or may not be obvious, e.g., differences in religious beliefs, gender, hearing, or sight. However, as clinicians we often neglect to assess tangata whaiora abilities to verbalise such information. Te Pounamu, as a Māori model demonstrates the underlying principles of Te Tiriti O Waitangi. Providing the best treatment outcomes is about acknowledging all aspects of one’s wellbeing: physical, mental, spiritual, and whānau. Te Pounamu provides a process that acknowledges such aspects in a way of knowing that is healing. From clinical experience, the interactive mode that Te Pounamu utilises has been found efficacious in assisting tangata whaiora to understand how such factors contribute to poor mental health.

year: 2003