In recent years, the furniture design trends include ensuring ergonomic standards, development of new environmentally friendly materials, optimised use of natural resources, and sustainably increased conversion of waste into value-added products. The circular economy principles require the reuse, recycling or upcycling of materials. The potential of reusing waste corrugated cardboard to produce new lightweight boards suitable for furniture and interior applications was investigated in this work. Two types of multi-layered panels were manufactured in the laboratory from corrugated cardboard and beech veneer, bonded with urea-formaldehyde (UF) resin. Seven types of end corner joints of the created lightweight furniture panels and three conventional honeycomb panels were tested. Bending moments and stiffness coefficients in the compression test were evaluated. The bending strength values of the joints made of waste cardboard and beech veneer exhibited the required strength for application in furniture constructions or as interior elements. The joints made of multi-layer panels with a thickness of 51 mm, joined by dowels, demonstrated the highest bending strength and stiffness values (33.22 N∙m). The joints made of 21 mm thick multi-layer panels and connected with Confirmat had satisfactory bending strength values (10.53 N∙m) and Minifix had the lowest strength values (6.15 N∙m). The highest stiffness values (327 N∙m/rad) were determined for the 50 mm thick cardboard honeycomb panels connected by plastic corner connector and special screw Varianta, and the lowest values for the joints made of 21 mm thick multi-layer panels connected by Confirmat (40 N∙m/rad) and Minifix (43 N∙m/rad), respectively. The application of waste corrugated cardboard as a structural material for furniture and interiors can be improved by further investigations.

In recent years, 3D printing technology has become very important in many fields of science, manufacturing, design, medicine, aviation, sports, etc. Furniture design and manufacturing are also not left out of this trend. In this study, the results of bending moments and stiffness of joints of thin structural elements connected by 3D printing with polylactic acid (PLA) connectors are given. The connectors are newly developed, and information on their strength characteristics is lacking in the literature. Ten joints were investigated, made with 9 and 12 mm plywood and 6 mm MDF. The tested joints constructed by 3D-printed connecting elements show a high strength under arm compression bending load, between 44.16 and 24.02 N·m. The stiffness coefficients of joints with 3D-printed connecting elements are between 348 and 145 N·m/rad and are higher than those of conventional detachable mitre joints but lower than those of glued ones. The type of filling of the hollow section of the connecting elements and the wall thickness influenced the joints’ strength and stiffness. Reducing the width of the connecting elements from 40 to 30 mm and the inner radius between the arms from 2 to 1 mm does not significantly affect the joints’ strength and stiffness coefficients.

One of the biggest challenges for designers and manufacturers of furniture is to reduce the thickness of conventional furniture materials such as particleboard (PB), medium-density fibreboard (MDF) and plywood. Designing furniture based on thin (less than 16 mm) and ultra-thin materials (less than 10 mm) is desirable for aesthetic reasons and because of the substantial material savings. However, the use of thin and ultra-thin materials reduces the strength of the furniture, especially the strength and deformation resistance of the joints. This study aimed to establish the possibilities for efficient furniture construction made of thin and ultra-thin materials using mitre joints. For this purpose, 14 types of L-type joints were tested: 12 glued and 2 detachable. The joints were made of eight wood-based panels and one non-wood panel. The bending moments and the stiffness coefficient under compression were determined. The obtained results show that the mitre joints made of laminated material with high-pressure laminate (HPL), 8 mm thick, MDF achieved the highest bending moment, and the highest stiffness coefficient was achieved by joints made of 10 mm thick compact HPL. Compact HPL joints were significantly affected by the type of adhesive used. Detachable joints had a relatively high bending strength but very low stiffness.

Acrylic solid surface composites made of poly (methyl methacrylate) (PMMA) and aluminum trihydrate, Al(OH)₃ (ATH) are widely used in furniture and interior applications. However, independent brand comparative data, especially on density-normalized (“specific”) properties, remain limited. This study quantifies the flexural response of 11 commercial sheets (6, 8, and 12 mm, including one translucent) under ISO 178 three-point bending and evaluates the effects of heating and cooling relevant to thermoforming. The density is concentrated in the range 1680–1748 kg/m³ (weighted mean of 1712 kg/m³). The flexural strength ranged between 51 and 79 MPa, divided into three groups—high (76–79 MPa), medium (63–67 MPa), and low (51–56 MPa) levels, while the modulus ranged between 7700 and 9400 MPa with a narrow dispersion. The strength showed no significant correlation with density, while the modulus increased with density, indicating that stiffness is composition-dominated, while strength is influenced by factors related to microstructural defects/particle boundaries. Heating at 160 °C and subsequent cooling have a significant influence on flexural strength and strain. Flexural strength increased by an average of approximately 7%, and flexural strain increased by approximately 12%, while the modulus remained virtually unchanged (within ±0.5%); additionally, shock cooling did not bring any benefits. The density-normalized parameters (σ/ρ, E/ρ) reflected these trends, allowing for a more accurate comparison when limited by mass or deformation. Overall, the results are broadly consistent with manufacturers’ declarations and demonstrate that thermoforming-relevant heating at 160 °C, followed by cooling, can be used not only to improve formability but also to modestly increase flexural strength and strain without compromising stiffness.

Quantitative data on the bending capacity and rotational stiffness of corner joints made from acrylic solid-surface PMMA/ATH composites are limited, despite their widespread use in furniture and interior components. The study provides comparative bending moment and rotational-stiffness benchmarks for 18 PMMA/ATH corner-joint series, using a stiffness-evaluation procedure tailored to corner-joint testing. L-type joints produced from two commercial PMMA/ATH materials (Kerrock and Corian) at 6- and 12-mm thickness were manufactured in 18 configurations, including glued butt, 45° mitre, reinforced mitre, rebate, groove variants, and detachable Minifix eccentric and Lamello Clamex connectors. Specimens were tested under arm-compression bending and maximum bending moment (M_max), and joint rotational stiffness was derived. The best-glued solution was the 12 mm Kerrock 45° mitre with M_max 186.21 N·m, whereas the strongest 6 mm joint reached 40 N·m. Reinforcing the 12 mm Kerrock mitre joint increased stiffness to 9521 N·m/rad but did not increase bending capacity relative to the non-reinforced mitre. Detachable joints formed a clearly distinct low-rigidity class with bending moments of 2.22–3.89 N·m and stiffness below 194 N·m/rad. Overall, thickness and joint geometry dominate both strength and stiffness, and the tested detachable connectors should be reserved for applications requiring disassembly rather than for load-bearing corners.