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The use of statistical methods for evaluating durability of adhesively bonded joints.

Twine, T J*; Broughton, W R (1999) The use of statistical methods for evaluating durability of adhesively bonded joints. NPL Report. CMMT(A)203

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This report presents a compilation of case studies that demonstrate the use of statistical methods in evaluating durability data generated in high humidity weathering conditions and accelerated laboratory tests. A number of case studies are based on data supplied by industrial organisations within the United Kingdom. The remaining case studies utilise data specifically generated within the experimental programme to evaluate key parameters (e.g. interaction between temperature and humidity) that influence long-term durability of adhesively bonded structures. Factors considered in the report include: (i) test method; (ii) surface treatment; (iii) adhesive type; (iv) processing variables (time, temperature and pressure); and (v) environmental conditions.
Statistical analysis has been used to determine the effect of high humidity weathering conditions (i.e. 95% humidity with the temperature cycled between 42 °C and 48 °C) on the performance of zinc and organic coated steel joints bonded with a range of adhesives (polyurethane, acrylic and epoxy). The data, supplied by British Steel Plc, was for a 12 month exposure period. Data, supplied by British Aerospace (Sowerby), relating to the lap shear and thick adherend shear test (TAST) methods conducted on two adhesives over the temperature range of -67 °F (-55 °C) to 350 °F (177 °C) have been compared in order to determine relative sensitivity and data variability for the two methods. A third case study examines data supplied to the programme by Alcan International Limited, in which a full factorial analysis is used to determine the optimum combination of processing variables for long-term durability performance.
The report concludes with two case studies based on durability data generated within the programme. The first demonstrates the use of a “Design of Experiment” approach to maximise information from an experiment, and simultaneously minimise the impact of spurious non-experimental, or “noise” factors, during the execution of the experiment. The case study concludes with an analysis of the results of the controlled experiment. The final case study considered in this report examines the interaction of temperature and humidity on residual strength of titanium alloy joints bonded with an epoxy structural adhesive. Single-lap joints were exposed to nine combinations of temperature (3 levels) and humidity (3 levels). A full factorial analysis has been carried out on the data to determine empirical relationships between the various factors of time, temperature and humidity.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CMMT(A)203
Subjects: Advanced Materials
Advanced Materials > Adhesives
Last Modified: 02 Feb 2018 13:18
URI: http://eprintspublications.npl.co.uk/id/eprint/1279

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