Short answer

Implement rigorous quality control during the lamination process to ensure consistent fibre orientation across all veneers, and refine material models for simulations to account for complex wood behaviour under environmental stress.

Field: Final Production
Source: BioResources (2019)
Method: Experimental study combined with finite element modelling (FEM).
Sample: 90 cross-laminated shells.
Evidence: Strong effect

Even minor deviations in fibre orientation within individual veneers of a laminated product can lead to substantial shape distortion when exposed to varying relative humidity. This final production research insight is drawn from a 2019 study published in BioResources. Using Experimental study combined with finite element modelling (fem). with 90 cross-laminated shells., researchers explored how this design variable affects real-world outcomes. The key design takeaway: Implement rigorous quality control during the lamination process to ensure consistent fibre orientation across all veneers, and refine material models for simulations to account for complex wood behaviour under environmental stress.

Study

Final ProductionHigh ImpactStrong effect

Fibre orientation deviation in laminated veneer significantly increases post-moulding distortion by up to 7° under humidity changes.

Even minor deviations in fibre orientation within individual veneers of a laminated product can lead to substantial shape distortion when exposed to varying relative humidity.

BioResources · 2019

Key Findings

01Deviation in fibre orientation of individual veneers significantly influences the shape stability of laminated products.
02The placement of a veneer with deviated fibre orientation impacts the degree of distortion.
03Finite element models significantly underestimated the observed distortion compared to experimental results, indicating complexity in modelling material behaviour.

Application

Design takeaway

How to apply

During the veneer layup stage, use jigs or visual inspection to ensure consistent alignment of grain direction across all plies. For critical applications, consider post-moulding stabilization treatments or material selection that minimizes hygroscopic expansion.

Project actions

01When selecting materials for a laminated design, research their dimensional stability under varying environmental conditions.
02If using wood or wood-based composites, pay close attention to grain direction and its potential impact on the final form.
03Consider how environmental factors like humidity and temperature might affect your design's performance over time.

Method & Evidence

AimTo investigate the influence of individual veneer fibre orientation deviation on the distortion of cross-laminated shells under relative humidity variations and to assess the predictive capability of finite element modelling.

MethodExperimental study combined with finite element modelling (FEM).

ProcedureCross-laminated shells were manufactured with birch veneers. Some shells incorporated individual veneers oriented at a 7° deviation from the main fibre orientation. These shells were then subjected to relative humidity variations, and the resulting distortion was measured. A finite element model was developed to simulate these conditions and compare its predictions with experimental results.

Sample90 cross-laminated shells.

ContextManufacturing of laminated veneer products, specifically moulded shells.

Variables

IVDeviation in individual veneer fibre orientation (e.g., 0° vs. 7°).

DVDegree of distortion in the laminated shell.

CVGeometrical shape of the shell, number of veneers, type of veneer (birch), initial straightness of veneers.

Strengths & Limitations

Strengths

+Combines experimental validation with theoretical modelling.
+Investigates a specific, practical manufacturing issue.
+Uses a substantial sample size for the experimental component.

Limitations

The study focused on birch veneer and specific humidity variations. Results might differ for other wood species, veneer types, or a wider range of environmental conditions. The FE model's accuracy is also a key limitation.

Reliability & validity

The study's reliability is supported by the experimental approach and the use of a relatively large sample size (90 shells). Validity is enhanced by directly measuring distortion under controlled humidity changes. However, the discrepancy between experimental results and FE modelling suggests potential limitations in the model's validity for predicting these specific outcomes.

Think critically

Given the limitations of current FE modelling in accurately predicting distortion in laminated veneer, what alternative or complementary methods could designers employ to ensure the dimensional stability of their products?

Design Principles

"Dimensional stability in composite materials is highly sensitive to internal structural alignment and environmental exposure."

This research highlights a critical factor in the manufacturing of laminated veneer products, directly impacting product quality and longevity. Understanding and controlling fibre orientation is essential for designers and manufacturers aiming to produce dimensionally stable components, especially in applications exposed to environmental fluctuations.

What This Means for Your Design

If you're making something out of layers of wood veneer, like a curved chair, make sure the wood grain in each layer is lined up correctly. If even one layer is slightly off, the whole thing can warp when the air gets more or less humid.

How to use in your project

1.Reference this study when discussing material properties and their influence on product performance, particularly concerning dimensional stability and environmental factors.
2.Use the findings to justify design choices related to material selection and manufacturing processes aimed at minimizing distortion.

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Quick Cite

Paragraph starter

The dimensional stability of laminated veneer products is significantly influenced by the orientation of fibres within individual veneers. Research by Blomqvist et al. (2019) demonstrated that even minor deviations (e.g., 7°) in fibre orientation can lead to substantial post-moulding distortion when exposed to relative humidity variations. This underscores the critical need for precise manufacturing controls to ensure product integrity and performance, especially in applications susceptible to environmental changes.

Source

BioResources

Distortion in laminated veneer products exposed to relative-humidity variations – Experimental studies and finite-element modelling

journal · 2019

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Questions About This Research

What does the research say about fibre orientation deviation in laminated veneer significantly increases post-moulding distortion by up to 7° under humidity changes?: Implement rigorous quality control during the lamination process to ensure consistent fibre orientation across all veneers, and refine material models for simulations to account for complex wood behaviour under environmental stress. Evidence: BioResources (2019).
Why does "Fibre orientation deviation in laminated veneer significantly increases post-moulding distortion by up to 7° under humidity changes." matter for design?: This research highlights a critical factor in the manufacturing of laminated veneer products, directly impacting product quality and longevity. Understanding and controlling fibre orientation is essential for designers and manufacturers aiming to produce dimensionally stable components, especially in applications exposed to environmental fluctuations.
How can designers apply this research?: Implement rigorous quality control during the lamination process to ensure consistent fibre orientation across all veneers, and refine material models for simulations to account for complex wood behaviour under environmental stress.
What were the main findings?: Deviation in fibre orientation of individual veneers significantly influences the shape stability of laminated products.. The placement of a veneer with deviated fibre orientation impacts the degree of distortion.. Finite element models significantly underestimated the observed distortion compared to experimental results, indicating complexity in modelling material behaviour.
What research method was used?: Experimental study combined with finite element modelling (FEM). with 90 cross-laminated shells..
How strong is the evidence?: Evidence strength is rated Strong effect, based on a 2019 journal from BioResources.
What should I do differently in my next project?: During the veneer layup stage, use jigs or visual inspection to ensure consistent alignment of grain direction across all plies. For critical applications, consider post-moulding stabilization treatments or material selection that minimizes hygroscopic expansion.
What are the limitations?: The FE model's underestimation suggests that factors such as veneer density variations, annual ring orientation, loose/tight side orientation, and moulding tool design parameters were not fully captured or accurately represented in the simulation.