# Relationship Between Hardness and Impact Strength of Epoxy–Glass Composites Modified with Carbonisate from MDF Pyrolysis

## TL;DR

This study shows how adding carbonisate from MDF waste improves the hardness of epoxy-glass composites but slightly reduces their impact resistance.

## Contribution

The novel use of MDF pyrolysis waste as a filler in composites is shown to enhance hardness with minimal impact on fracture resistance.

## Key findings

- Increasing carbonisate content improves surface hardness but reduces impact resistance.
- The optimal composite had 7.5% carbonisate and a 60/40 resin-reinforcement ratio.
- Statistical analysis confirmed significant differences and a trade-off between hardness and impact strength.

## Abstract

The study analysed epoxy–glass laminates containing carbonisate produced during medium-density fibreboard (MDF) waste pyrolysis were evaluated with respect to their hardness and their ability to withstand impact loads. All composite samples were prepared manually using a hand-laying method, using two resin–reinforcement ratios (60/40 and 65/35) and carbonisate additives in amounts of 5% and 7.5% by weight (with particle sizes < 500 µm). The mechanical properties were assessed on the basis of hardness tests using the Barcol method and impact tests using the Charpy method. To analyse the results, a normality assessment (Shapiro–Wilk) was performed, followed by a non-parametric analysis of variance based on ranks (Kruskal–Wallis). It was found that an increase in carbonisate content increases the surface hardness of composites while reducing their impact resistance, which confirms the existence of a typical trade-off between stiffness and energy absorption capacity. The most favourable mechanical properties were obtained for a composite containing 7.5% carbonisate material and a resin–reinforcement ratio of 60/40, which was characterised by the highest hardness (35.19 HBa), a moderate impact strength (43.56 kJ/m2) and the lowest variability of results. The statistical analysis confirmed significant differences between the tested samples and a quantitative relationship between hardness and impact strength. The results of the study indicate that carbonisate (MDF) using waste material as a filler provides a sustainable means of improving the stiffness and consistency of epoxy–glass composites, with only a negligible effect on their ability to resist fracture.