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Title: A study of thermal strains in glass fibre reinforced plastics
Author: Mulheron, Michael John
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1984
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The temperature dependence of the thermal strain in cross-ply glass fibre reinforced epoxy and polyester resin laminates has been determined from the deflection of unbalanced (0 /90) composite beams. These results have been compared with those predicted from measured values of the linear thermal expansion coefficients and moduli of the individual plies. For the epoxy resin based laminates good agreement was found between the experimental and calculated values. For the polyester resin based laminates, however, the predicted values considerably underestimated the experimentally determined thermal strain. The longitudinal and transverse expansion coefficients of dry post-cured unidirectional laminates made using these two resins were consistent with predictions from the Schapery equations, provided the temperature dependence of the resin expansion coefficient was allowed for. Small quantities of absorbed water were found to significantly increase the expansion coefficient of the polyester resin while leaving that of the epoxy resin unaffected. As a result of this effect fully post-cured polyester laminates containing absorbed water demonstrated a significant increase in the transverse expansion coefficient with little change in the longitudinal value. Using values of the thermal expansion coefficient for a polyester laminate containing 0.15 wt% water, good agreement between predicted and experimental values of thermal strain was obtained. Therefore the large thermal strains reported for polyester cross-ply laminates can be explained by small quantities of water in the matrix resin which is not readily removed during post-curing. The sensitivity of the polyester resin to such small quantities of absorbed water is considered to result from a two-phase microstructure consisting of highly cross-linked nodules in a less densely cross-linked matrix.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available