Strain Distribution and Load Transfer in the Polymer-Wood Particle Bond in Wood Plastic Composites

Strain Distribution and Load Transfer in the Polymer-Wood Particle Bond in Wood Plastic Composites Matthew J. Schwarzkopf Lech Muszyński John Nairn Department of Wood Science and Engineering, Oregon State University, Corvallis, OR

Es, (MPa) UTS, (MPa) Do we understand these results? Secant Modulus ASTM D638 Ultimate Tensile Stress ASTM D638 30 3,000 2,500 2,000 25 20 1,500 15 1,000 10 500 PF WJ FT UW HDPE 0 0.00 0.20 0.40 0.60 0.80 Loading Ratio, (kg/kg) 5 PF WJ FT UW HDPE 0 0.00 0.20 0.40 0.60 0.80 Loading Ratio, (kg/kg) Source: Karas, M

Figure: Clyne, T.W. Photo: Wang, Y

Figure: Clyne, T.W.???

Create an efficient method for the measurement of strain patterns of wood particles embedded in a polymer matrix Couple these empirical measurements with material point method (MPM) numerical modeling using inverse problem methodology

Tensile tests on polymer specimens with embedded particles Observe strain patterns in the particle-matrix interphase Make the test output compatible with numerical modeling software A. Experiment C. Numerical simulation of the experiment B. Experimental results D. Simulation results Difference (Δ) Figure: Clyne, T.W. Property input Adjust property Sensitivity analysis Stop No Δ Yes Prop.

Particles and HDPE mixed HDPE and particles mixed in a blender Molded in a hot press, 1mm thick Wood Particles 0 90 45 Specimens punched out of film Reference Particles

Cross section of particle embedded in HDPE X-ray Computed Tomography Distance from Surface Embedded Wood Particle

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A pattern is applied to the surface of the specimen which provides unique patterns for the computer to recognize. Air Air deposition of laser toner 1 mm 1 mm Reference Specimen Wood Specimen

3D DIC provides full field, non-contacting optical measurements of displacements and strains Tension Tension Particle-Matrix Interphase Embedded Specimen Embedded Specimen

Figure: Clyne, T.W. Reference Particle Analysis Observed Principle Strain Particle Theoretical Observed Shear Strain Particle

Reference Particle Analysis Principal Strain Plots Distance from Surface Embedded Particle

Reference Particle Analysis Principal Strain Plots and Depth from Surface 0.004 mm 0.020 mm 0.100 mm

Reference Particle Analysis Quantitative descriptors Particle length [mm] Particle orientation [degrees from X] Particle distance from the surface [mm] Area of ZOI surface section [mm 2 ] Derivation Measured Measured Measured Measured Equivalent radius of ZOI Circularity of ZOI [r 2 ] Ratio of ZOI equivalent radius to the particle length for 0 and 90 specimens [mm mm -1 ] Ratio of ZOI minor dimension to the particle depth for 45 specimens [mm mm -1 ] Calculated

Reference Particle Analysis

Based on Grediac, M. and F. Pierron, 1998 A. Experiment & imaging C. Morph. Modeling Material property input B. Experimental Results ε 1 (DIC) D. ε 1 from model Adjust property Sensitivity analysis Difference (Δ) Stop No Δ Yes Prop.

An efficient methodology was created for the preparation, testing, optical measurement, and analysis of single wood particles embedded in a polymer matrix Coupling of optical measurements with MPM modeling and inverse problem methodology provided good qualitative agreement of strain patterns of the particle-matrix interphase A. Experiment & imaging C. Morph. Modeling Difference (Δ)

Dr. Lech Muszynski Dr. John Nairn Xiang Lin Farzana Hussain