Characterization of Maple and Ash Material Properties for the Finite Element Modeling of Wood Baseball Bats  
[PERSON]  
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[PERSON]  
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[PERSON]  
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[PERSON]  
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in the late 1990s. Maple became the trendy choice after [PERSON] historic 2001 season in which he set a MLB single-season record of 73 homeruns using a maple bat. To develop a baseline on the rate of bat breakage, MLB completed a two-and-a-half-month collection of broken bats in August 2008. The lessons learned from this and subsequent wood bat collections led to new requirements in the WBBS (Wooden Baseball Bat Specifications), specifically ash bats continue to be impacted on the edge grain, maple bats change to be impacted on the face grain and the slope-of-grain (SoG) of the wood used to manufacture baseball bats to be within \(\pm 3^{\circ}\) of the centerline of the bat longitudinal axis. To complement the wood bat collections, research efforts were conducted to investigate how finite element modeling can aid in explaining how bat profile and wood quality relate to bat durability [1]. Previous research studies conducted on metal, composite and wood baseball bats utilizing the finite element method have been demonstrated to be an effective way of analyzing the effect of high-speed impact on the bat after impact with the baseball occurs [2; 3; 4; 5]. These finite element models have been found to be valuable tools for providing insight into the mechanical response of wood baseball bats over a range of impact speeds [6]. However, the description of the material properties to date has been limited to what can be extracted from quasistatic four-point bend testing of dowels and from the Wood Handbook [7]. These quasistatic test programs were completed at the USDA (United States Department of Agriculture) Forest Product Labs (FPL) and have documented the Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) for ash, maple and yellow birch as a function of wood density [8]. To further improve the level of correlation between these finite element models and lab-simulated bat/ball impacts, the material behavior for these wood species must also be characterized at strain rates comparable to those experienced during game-condition bat/ball collisions. In the current research, Charpy Impact testing of ash and maple was completed to characterize the high strain-rate behavior of these wood species. To date the documented research on the dynamic behavior of wood during impact is fairly limited [9; 10] compared to other engineering materials. By following the testing methodologies that were used by the Federal Highway Administration (FHWA) [11] to characterize southern yellow pine and applying them to maple and ash, the current high-speed testing characterized the material behavior of these wood species further than is currently available. Once characterized, the resulting material properties can be prescribed in the *MAT_WOOD (Material Model 143) and *MAT_EROSION material models in LS-DYNA for use in finite element analyses of bat/ball impacts. In addition to the mechanical testing data from the FPL and the Charpy programs, past test data for maple and ash bats in the ADC Bat Durability Testing System that are available at the UMass Lowell Baseball Research Center (UMLBRC) [1; 12] along with properties taken from the Wood Handbook [7] were utilized to further refine wood properties. With a level of confidence in the material parameter inputs established, the finite element modeling can be used to support scientifically defensible arguments for proposing future changes to wood bat specifications aimed at reducing bat breakage rates. In some cases, these changes can be essentially transparent to players as to what they have come to expect in bat feel and performance. This paper describes the Charpy test program that was used to characterize the strain-to-failure of ash and maple wood specimens under dynamic loading and the subsequent finite element modeling using the material parameters derived from the test program.