ENHANCING THE COMPRESSIVE PERFORMANCE OF BASALT/EPOXY PULTRUDED RODS USING POLYHEDRAL OLIGOMERIC SILSESQUIOXANE (POSS) AS NANO-REINFORCEMENT
Topic(s) : Manufacturing
Co-authors :
Eleni GEORGIOU (UNITED KINGDOM), Gustavo QUINO (UNITED KINGDOM), Ian HAMERTON , Richard S. TRASKAbstract :
1 Introduction
Continuous fibre reinforced polymers (FRPs) have become increasingly popular for advanced structural applications in the aerospace, wind energy, marine, and automotive sectors. However, longitudinal compression failure is a design limiting factor, with compression strength being up to 60% lower than the tensile strength for a given composite material [1]. With compressive loads arising in structures intentionally and otherwise, the safety margins accounted for at the design stages often result in overdesigned and inefficient structures [2]. Compressive failure is typically governed by matrix or fibre-matrix interface shearing at regions with high degrees of fibre misalignment.
In this study, we consider the manufacturing and testing of toughened resin/natural fibre pultruded rods which will be used to fabricate a hierarchical ply-level structure to improve the compressive performance of sustainable fibre constructs. Pultrusion is becoming increasingly popular with industry due to its cost effectiveness, good part quality, and minimal waste production for constant cross-section profiles. Critically to this investigation, resin-bath pultrusion facilitates the manufacture of composites with a high degree of fibre alignment. The addition of POSS, which is a functionalised cage-like organic-inorganic hybrid nanoparticle, to a commercial LY556/XB3473 epoxy will be explored to increase the resin strength and modulus, therefore potentially increasing the composite compressive strength. Basalt fibre is chosen to demonstrate the applicability of the methods to more sustainable fibres for structural purposes, and to improve confidence in natural fibres via mechanical characterisation.
2 Experimental
We will present our latest investigations on pultruded basalt/epoxy rods, which have been tested in compression using the “cradle test”. This consists of a PMMA beam under four-point bending with the rod on the compression side[3]. The effects of process variability of pultrusion on the compressive strength is explored. Tests were quasi-static and conducted using a servo-hydraulic Instron 8872 machine. Surface strains were measured using Digital Image Correlation (DIC) and force histories were obtained from the load cell. The effects of the addition of POSS to the epoxy on the thermal and mechanical properties of the rods are discussed with reference to the un-modified epoxy. The effect of heating zone temperatures and initial resin viscosity on the rod void and matrix contents are investigated using optical microscopy and used as evidence for the observations seen in testing. The influence of POSS on the compressive performance will be discussed leading to clear recommendations for the future manufacture of optimised natural fibre structures for sustaining in-service compression loads.
Continuous fibre reinforced polymers (FRPs) have become increasingly popular for advanced structural applications in the aerospace, wind energy, marine, and automotive sectors. However, longitudinal compression failure is a design limiting factor, with compression strength being up to 60% lower than the tensile strength for a given composite material [1]. With compressive loads arising in structures intentionally and otherwise, the safety margins accounted for at the design stages often result in overdesigned and inefficient structures [2]. Compressive failure is typically governed by matrix or fibre-matrix interface shearing at regions with high degrees of fibre misalignment.
In this study, we consider the manufacturing and testing of toughened resin/natural fibre pultruded rods which will be used to fabricate a hierarchical ply-level structure to improve the compressive performance of sustainable fibre constructs. Pultrusion is becoming increasingly popular with industry due to its cost effectiveness, good part quality, and minimal waste production for constant cross-section profiles. Critically to this investigation, resin-bath pultrusion facilitates the manufacture of composites with a high degree of fibre alignment. The addition of POSS, which is a functionalised cage-like organic-inorganic hybrid nanoparticle, to a commercial LY556/XB3473 epoxy will be explored to increase the resin strength and modulus, therefore potentially increasing the composite compressive strength. Basalt fibre is chosen to demonstrate the applicability of the methods to more sustainable fibres for structural purposes, and to improve confidence in natural fibres via mechanical characterisation.
2 Experimental
We will present our latest investigations on pultruded basalt/epoxy rods, which have been tested in compression using the “cradle test”. This consists of a PMMA beam under four-point bending with the rod on the compression side[3]. The effects of process variability of pultrusion on the compressive strength is explored. Tests were quasi-static and conducted using a servo-hydraulic Instron 8872 machine. Surface strains were measured using Digital Image Correlation (DIC) and force histories were obtained from the load cell. The effects of the addition of POSS to the epoxy on the thermal and mechanical properties of the rods are discussed with reference to the un-modified epoxy. The effect of heating zone temperatures and initial resin viscosity on the rod void and matrix contents are investigated using optical microscopy and used as evidence for the observations seen in testing. The influence of POSS on the compressive performance will be discussed leading to clear recommendations for the future manufacture of optimised natural fibre structures for sustaining in-service compression loads.