###### Abstract  
The mechanical properties of sliced lamellae are critical for structural and decorative engineered wood products. This study evaluates the impact of slicing thickness on the tensile mechanical properties of plain oak (_Quercus robur_ L. and _Quercus petraea_ L.) sliced lamellae, perpendicular to the grain direction. The mechanical performance parameters in terms of the modulus of rupture (MOR), strain at break, and modulus of elasticity (MOE), were analysed using a one-way analysis of variance (ANOVA) and contrast analysis. Our findings indicate that slicing thickness substantially affects the mechanical properties of the modulus of rupture and strain at break, whilst the modulus of elasticity was somewhat independent of the slicing thickness. The mean MOR value increased from 0.8 to 1.43 N mm\({}^{-2}\) for an increase in the sliced lamellae thickness from 1.5 to 4.5 mm. The strain at break increased, on average, from 1.37 to 2.64% for an increase in the sliced lamellae thickness from 1.5 to 4.5 mm. The MOE was approximately 100-120 N mm\({}^{-2}\), indicating a substantially reduced stiffness compared to other sliced lamellae species and solid oak reported values. The slicing check depth ratio diminished from approximately 69% to 50% for an increase in the sliced lamellae thickness from 1.5 mm to 4.5 mm. These findings indicate a negative correlation between the slicing check depth ratio and the tensile performance perpendicular to the grain, suggesting the importance of obtaining an optimal slicing quality. This study employs digital image correlation (DIC) analysis to gain insights into the fracture mechanisms of the tested sliced lamellae and provides an alternative method for strain and stress measuring. The DIC analysis highlighted the role of slicing checks in the stress concentration and ultimate failure areas. This research provides insights into the fracture behaviour of sliced lamellae that are perpendicular to the grain, which is critical for the performance of both structural and decorative products. v 2023 20  
extended to a series of multi-layered products such as engineered wood flooring, interior panels, and furniture. The potential impact of extensively using sliced lamellae for joinery products is high; for example, the engineered wood flooring market is estimated at nearly 90 mln. m\({}^{2}\) in Europe alone [3]. The main advantage of the slicing technique over traditional sawing is an increased yield due to no kerr being required when cutting. Due to the kerrless cutting aspect, slicing produces fewer combustion-use by-products than sawing, allowing for the sustainable and cascaded use of the wood raw material. Moreover, slicing technology may increase the fire and health safety of production units compared to traditional sawmills. Hence, the main advantage of the slicing technique resides in producing thin wood elements without compromising the surface quality; therefore, a high volume-to-area conversion ratio is achieved. Plain and lengthwise slicing are the most common flat slicing techniques [4]. Plain slicing is performed on vertical slicers where the cutting is perpendicular to the material direction, similar to a 0-90 cutting situation [5]. Lengthwise slicing is performed on horizontal slicers using a highly oblique slicing knife and occurs when cutting parallel to the grain, following the specimen feed direction. The advantage of plain slicing over lengthwise slicing is the increased processing speed [6]. Material cutting in slicing occurs via wood compression in front of the knife's cutting edge, assisted by a pressure bar displaced on the back-side of the cut veneer. The role of the pressure bar is to counter excessive tensile forces perpendicular to the grain that would lead to lamellae collapse [4; 5]. Hence, parts of the cutting energy may not be countered in the slicing process, and it is released by generating small cracks, known as lathe or slicing checks [5]. Slicing checks are a significant quality issue of sliced lamellae and sliced-lamellae-based products.