Abstract
Novel bio-based composite wood panels (CWPs) that consisted of distiller’s dried grains and solubles (DDGS) flour adhesive bound to a wood filler/reinforcement were subjected to high strain-rate compression loading, and their behavior was investigated. Specimens of DDGS-Paulownia wood (PW) or DDGS-pinewood (Pine) composites made using DDGS with fractions of 10%, 15%, 25%, and 50% were tested at high strain-rates using a modified compression Split Hopkinson Pressure Bar (SHPB). Both DDGS-PW and DDGS-Pine composites displayed strain-rate sensitivity, and DDGS-PW had a 25% fraction, which showed the highest ultimate compressive strength of 655 MPa at approximately 1600/s. The 90%-PW had the highest specific energy of 19.24 kJ/kg at approximately 1600/s when loaded via dynamic compression. The CWPs constructed of DDGS-PW had higher strength and energy absorption than DDGS-Pine with the exception of the 50% DDGS composites.
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High Strain-rate Dynamic Compressive Behavior and Energy Absorption of Distiller’s Dried Grains and Soluble Composites with Paulownia and Pine Wood Using a Split Hopkinson Pressure Bar Technique
Damian Stoddard,a,* Suman Babu Ukyam,a Brent Tisserat,b Ivy Turner,a Rowan Baird,a Sofia Serafin,a Jose Torrado,a Birendra Chaudhary,a Alex Piazza,a Mason Tudor,a and Arunachalam M. Rajendran a
Novel bio-based composite wood panels (CWPs) that consisted of distiller’s dried grains and solubles (DDGS) flour adhesive bound to a wood filler/reinforcement were subjected to high strain-rate compression loading, and their behavior was investigated. Specimens of DDGS-Paulownia wood (PW) or DDGS-pinewood (Pine) composites made using DDGS with fractions of 10%, 15%, 25%, and 50% were tested at high strain-rates using a modified compression Split Hopkinson Pressure Bar (SHPB). Both DDGS-PW and DDGS-Pine composites displayed strain-rate sensitivity, and DDGS-PW had a 25% fraction, which showed the highest ultimate compressive strength of 655 MPa at approximately 1600/s. The 90%-PW had the highest specific energy of 19.24 kJ/kg at approximately 1600/s when loaded via dynamic compression. The CWPs constructed of DDGS-PW had higher strength and energy absorption than DDGS-Pine with the exception of the 50% DDGS composites.
Keywords: Bio-based adhesive; Dried Distiller’s Grain and Solubles (DDGS); Engineered wood composite; Split Hopkinson Pressure Bar (SHPB); Energy Absorption; Paulownia wood (PW); Pinewood (Pine)
Contact information: a: Mechanical Engineering Department, University of Mississippi, 229 Carrier Hall, University, MS 38677, USA; b: Functional Foods Research Unit, National Research Center for Agricultural Utilization, Agricultural Research Service, U.S. Department of Agriculture, Peoria, IL 61604, USA; *Corresponding Author: DLStodda@olemiss.edu
INTRODUCTION
By 2030, global consumption of industrial and solid wood is predicted to increase by 60% (Elias and Boucher 2014). Engineered wood products, including composite wood panels (CWPs) (e.g., fiberboards, particleboard, medium density fiberboard, and high density fiberboards) are an important material in the building and furniture industries (Woodpansonline 2015; Grand View Research 2018; Displays2GO 2019). The global CWP market is valued at approximately $91 billion (Woodpansonline 2015). Composite wood panels are designed precisely as per international standards to meet the increasing demand for wood in various applications, such as domestic housing projects and industries. Currently, CWPs are composed of a matrix adhesive (typically a synthetic resin) that binds wood particles, fibers, or veneers of wood together using heat and pressure. Composite wood panels fulfill certain applications that solid wood cannot perform due to their dimensional versatility and overall isotropic strength obtained through the design process. Composite wood panels are available in a wide variety of thicknesses, sizes, and grades to meet application-specific performance requirements.
Composite wood panels manufactured using petroleum-based resins emit volatile organic compounds, such as formaldehyde (Sawyers 2009; Grand View Research 2018). Formaldehyde is a known carcinogen and has adverse environmental and health consequences (Sawyers 2009; Grand View Research 2018). Several bio-adhesives have employed soy adhesives, which is the most common bio-adhesive employed currently; however, there are numerous alternative bio-based adhesives such as tannins, lignins, starch etc. (Amaral-Labat et al. 2008; Frihart and Birkeland 2016; Vnučec et al. 2016; Ghahri and Mohebby 2017; Hemmilä et al. 2017). Soybean flour proteins are abundant, renewable, biodegradable, and free of formaldehyde. Soy flour adhesives have high adhesion strength; however, they are more expensive than synthetic urea-formaldehyde and phenol-formaldehyde resins (Vnučec et al. 2016). The protein portion of the soy flour is responsible for its adhesive properties (Amaral-Labat et al. 2008; Frihart and Birkeland 2016; Vnučec et al. 2016; Ghahri and Mohebby 2017; Hemmilä et al. 2017). Defatted soy flour contains approximately 50% protein (Amaral-Labat et al. 2008; Frihart and Birkeland 2016; Ghahri and Mohebby 2017). Alternatively, distiller’s dried grain and solubles (DDGS) obtained from dry mill processing is a less expensive bio-based adhesive (USGC 2017). In the United States, the main feedstock for the production of ethanol is corn. Distiller’s dried grain and solubles is a byproduct of the ethanol fermentation process from corn (Pažitný et al. 2011). In 2017, approximately 90% of U.S. ethanol was produced from 214 dry grind ethanol plants. As a result, about 36.5 million metric tons of distiller’s co-products were expected to be produced in 2017 (USGC 2017). Distiller’s dried grain and solubles is composed of approximately 30% protein, 10% oil, and 54% carbohydrates, and it has a 10% moisture content (USGC 2017). In addition, DDGS has a long shelf life and can be shipped to locations far from the ethanol production facility.
Previously, DDGS has been employed as an inert low-cost bio-filler with phenolic resin to produce composites of high flexural strength (Cheesbrough et al. 2008). Tisserat et al. (2013b) produced plastic composites of high-density polyethylene (HDPE) matrices and reinforced them with solvent-extracted DDGS that exhibited superior tensile and flexural properties but lower impact energy properties than neat HDPE. Recently, Tisserat et al. (2018a, 2018b) fabricated CWPs composed of a DDGS matrix reinforced with Paulownia wood (PW). These DDGS-PW composite panels exhibited flexural and water resistance properties similar to soy flour-PW composites. In addition, the panels exhibited flexural properties that satisfy the industry standards. However, these CWPs had inferior water resistance, which suggests that their use may be limited to interior applications.
Typically, commercial CWPs are manufactured from sawn wood wastes (i.e., scraps, chips, and sawdust) of various species. However, this study utilized two different wood types as reinforcement components: Paulownia (PW) (Paulownia elongata) and Eastern White Pine (Pinus ponderosa). Paulownia is a fast-growing biomass tree that will likely become a source of woody biomass in the future (Joshee 2012; Sutton 2019). Paulownia is notable because it is a lightweight hardwood (Joshee 2012; Sutton 2019). It is employed in the furniture industry due to its light weight and pale appearance that typically has minimal knots. Paulownia has also been employed to manufacture wood-plastic composites that are relatively light but exhibit strong reinforcement properties (Tisserat et al. 2013a,c). The eastern white pine is a lumber tree grown throughout the north-eastern regions of the US and Canada (Wendel and Smith 1990; ACS 2019).
In many structural applications, engineered wood composites are subjected to dynamic loading conditions. The energy absorption and dissipation capabilities of composites are important during impact events. Thus, a detailed understanding of the dynamic behavior and energy absorption characteristics of engineered wood composites is warranted.
The Split Hopkinson Pressure Bar (SHPB) experimental technique has often been used to evaluate fiber-reinforced composites at high strain-rates. Allazadeh and Wosu (2011) reported the dynamic response of dry maple wood under a high strain-rate compressive loading using an SHPB. Results indicated that the damage mode was dependent on the incident energy, strain-rate, geometrical dimensions, and material structure. Widehammar (2004) performed dynamic tests to study the stress-strain relationships for spruce wood, and he established that wood behavior is greatly influenced by strain-rate, moisture content, and loading direction. In this study, the dynamic compression tests were performed on DDGS-PW and DDGS-Pine (Pine wood) wood composite specimens on a modified SHPB to determine the strain-rate sensitivity and ultimate compressive strength.
EXPERIMENTAL
Materials and Methods
The DDGS employed is marketed as a commercial animal corn feed pellet product, and it was procured from Archers Daniel Midland Co. (Chicago, IL, USA). Pine wood shavings were obtained from commercially sold pet bedding (Petsmart, Phoenix, AZ, USA). Paulownia wood was harvested from 36-month-old trees grown in Fort Valley, GA (Fort Valley State University, Fort Valley, GA, USA) and were then shipped to the USDA-NCAUR laboratory for processing. First, the paulownia was chipped several times through a chipper to obtain suitable shavings. Pine wood and PW were then milled using a Model 4 Thomas-Wiley mill grinder (Thomas Scientific, Swedesboro, NJ, USA) to reduce their size. Sizing of PW and Pine wood particles was conducted with a Ro-TapTm Shaker (Model RX-29; W.S Tyler, Mentor, OH, USA) to obtain one particle size selection of ≤ 600 µm and another size selection of 600 µm to 1700 µm particles. The PW and Pine contained approximately 6% moisture. The DDGS was first ground in a Wiley mill using a 2-mm opening sieve to obtain fine particles, and it was then defatted with hexane using a Soxhlet extractor. Defatted DDGS contained 30% crude protein and 5% moisture. The DDGS was ground into a flour consistency using a laboratory grinder (Ririhong Model RRA-500, Shanghai Yuanwo Industrial and Trade Company, Shanghai, China) and sieved to obtain particles of ≤ 250 µm.
Theory/Analysis
The DDGS-PW and DDGS-Pine composites were fabricated with 10% to 50% DDGS and paulownia or pinewood through a phase change process. The DDGS reacted with PW or Pine particles under high pressure and temperature to become a “liquid-gel” matrix and interfacial bond to the wood to produce CWPs, as shown in Fig. 1. Four different 10-mm-thick particleboards were constructed for each wood constituent type: 10% DDGS-90% wood; 15% DDGS-85% wood, 25% DDGS-75% wood, and 50% DDGS-50% wood. Samples of each variant with dimensions of 10 mm × 10 mm × 10 mm were prepared to maintain an aspect ratio of 1 for SHPB testing.
