Ultimate Strength of Quasi-Isotropic Composites: ISO 12215-5:2019 Validation

Glass fibre reinforced polymer composites are the most common materials employed for the manufacturing of small crafts, with the scantlings governed by ISO 12215-5:2019. However, no validation data is available to ascertain the relevance of the default ultimate strengths provided by the standard. This paper experimentally characterises the ultimate flexural, tensile and compressive strength of hand laminated and vacuumed bagged quasi-isotropic glass-epoxy laminate. The results show that ISO 12215-5:2019 default ultimate strengths for the quasi-isotropic composite laminate tested are (i) conservative for the ultimate flexural strength, (ii) appropriate for the ultimate tensile strength, and (iii) optimistic for the ultimate compressive strength, especially for vacuum bagged samples, with the main cause identified as the value of the ultimate compressive breaking strain for chopped strand mat. These findings provide validation data for ISO12215-5:2019 and it is anticipated the results may contribute to future improvements in small craft regulations.