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Dive into the research topics where Lloyd V. Smith is active.

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Featured researches published by Lloyd V. Smith.


Journal of Thermoplastic Composite Materials | 2000

Effects of Moisture on the Durability of a Wood/Thermoplastic Composite

Sudarshan V. Rangaraj; Lloyd V. Smith

The effects of simulated marine environments on the performance of wood/thermoplastic composites under quasi-static and fatigue loading is investigated. The material under consideration consists of wood flour embedded in a thermoplastic matrix. The effects of additives and processing methods were included in the durability study. Moisture sorption studies are presented for these formulations and are found to compare favorably with a linear Fickian diffusion model. Qualitative and quantitative evidence of hygrothermal damage was nevertheless consistently observed. The combination of Fickian diffusion and damage is explained from moisture-induced swelling considerations of the constituents. The influence of marine environments on fatigue response was examined by immersing the coupons in seawater during the fatigue test. The synergistic effects of moisture and fatigue are discussed.


Journal of Composite Materials | 2002

Isolating Components of Processing Induced Warpage in Laminated Composites

David A. Darrow; Lloyd V. Smith

This study considers laminate warpage (or spring-in) associated with the curing of reinforced thermoset composites. This processing induced spring-in shows up in flat parts as well as those with curved geometry, and is most prevalent with parts that do not have a closed cross section. Three contributions to spring-in were considered, namely: thickness cure shrinkage, mold expansion, and fiber volume fraction gradients. These effects were combined into a predictive finite element model (FEM). Mold stretching and thickness shrinkage were described through a modified in-and out-of-plane material thermal expansion, respectively, while fiber volume fraction gradients were accounted for by scaling the thermal and elastic properties of the composite through the thickness with the fiber volume fraction. For thin parts (< 2 mm) spring-in was dominated by fiber volume fraction gradient and mold stretching effects. For thick parts (> 2 mm) spring-in was dominated by thickness cure shrinkage. The FEM was able to account for 80% of the observed spring-in for parts ranging between 1 and 5 mm thick and having a 3 to 13 mm bend radius. This study shows that a relatively simple, linear-elastic analysis, can accurately describe competing contributions to spring-in over a range of material types and thicknesses.


Composite Structures | 2001

Performance assessment of wood, metal and composite baseball bats

Mahesh M Shenoy; Lloyd V. Smith; John T. Axtell

Abstract The purpose of this investigation was to develop and verify a predictive capability of determining baseball bat performance. The technique employs a dynamic finite element code with time dependent baseball properties. The viscoelastic model accommodates energy loss associated with the baseballs speed dependent coefficient of restitution (COR). An experimental test machine was constructed to simulate the ball–bat impact conditions in a controlled environment and determine the dynamic properties of the baseball. The model has found good agreement with the experimental data for a number of impact locations, impact speeds, bat models and ball types. The increased hitting speed generally associated with aluminum bats is apparent, but not for impacts inside of the sweet spot. A reinforcing strategy is proposed to improve the durability of wood bats and is shown to have a minimal effect on its hitting performance. The utility of using a constant bat swing speed to compare response of different bat types is also discussed.


Mechanics of Time-dependent Materials | 1999

The Nonlinearly Viscoelastic Response of a Wood-Thermoplastic Composite

Sudarshan V. Rangaraj; Lloyd V. Smith

This study considers the time-dependent response of a woodthermoplastic composite. The extruded material under considerationconsists of wood flour embedded in a high-density polyethylene (HDPE)matrix. The characterization study is based on a series of creep andrecovery tests. Stiffness reduction (i.e. damage) and permanentdeformation was observed in the material when the creep stress amplitudeexceeded a threshold value. The damage and permanent strains were foundto depend on creep stress amplitude and duration. The permanentdeformation was more efficiently accommodated by considering the coupontotal strain, however. A nonlinearly viscoelastic model is presentedthat incorporates damage and permanent deformation effects. Damage wasmodeled by considering an effective stress. The model is shown tocompare favorably with the experimental creep/recovery data as well astwo-step load history verification tests.


Journal of Thermoplastic Composite Materials | 2004

Nonlinear Viscoelastic Response of a Wood–Plastic Composite Including Temperature Effects

Douglas J. Pooler; Lloyd V. Smith

Current timber waterfront structures require the use of treated lumber to reduce environmental damage. Wood–plastic composites (WPCs) have been proposed as an alternative to treated timber due to their potential for reduced water absorption and degradation without chemical treatment. Even though WPCs are primarily made of wood (58% wood flour in the current case) their mechanical response to applied loads is quite different. The current study attempts to describe the time and temperature dependence of a commercial WPC formulation. Characterization of the formulation was undertaken by means of a series of creep and recovery tests. A Prony Series was used to describe the material’s time dependent compliance, where time was shifted with stress and temperature to describe the observed nonlinear response and temperature dependence. Damage effects were successfully correlated isothermally using an effective stress. The model was evaluated by comparing the behavior predicted by the model with experimental results in 3-point bending and fatigue.


Journal of Sports Sciences | 2009

Progress and challenges in numerically modelling solid sports balls with application to softballs

Lloyd V. Smith; Joseph G. Duris

Abstract Much of the work surrounding finite element simulation of bat–ball impacts has focused on techniques describing the ball. Determining the accuracy of these models has been hindered by challenges in experimentally characterizing the balls response. In the following, dynamic mechanical analysis and an instrumented impact test were used to characterize the solid ball at deformation rates representative of play. The ball was described in the numerical model as a linear viscoelastic material. It was observed that a Prony series model based on small deformation dynamic mechanical analysis did not provide sufficient energy loss upon impact, while a simpler Power Law model, fitted to large deformation data, described the measured energy loss and impact force over a range of speeds. Results of a parametric study are presented as a guide towards tailoring the parameters of the Power Law model to match the measured energy loss and impact force. Discrepancies observed between the experiment and the numerical model suggest that the ball response should be characterized in environments closely resembling game conditions.


Mechanics of Time-dependent Materials | 1997

Inelastic Behavior of Randomly Reinforced Polymeric Composites under Cyclic Loading

Lloyd V. Smith; Y.J. Weitsman

This study examines the development of damage in randomly reinforced polymeric composite materials. The material under consideration was made in a structural reaction injection molding process (SRIM) involving a continuous strand swirl mat of E-glass fibers and a urethane matrix. Theobjective of this work is to establish a predictive deformation model based on principles of viscoelasticity, damage mechanics and plasticity which maybe experimentally verified. Tests involving creep above a threshold stress level and recovery after load removal showed evidence of damage that was uniformly distributed throughout the coupon in the form of multitudes of matrix micro-cracks. Previous studies have shown that the material possesses a void content of about 5% and exhibits material property scatter of about 20%. The effects of damage could be assessed only when the scatter was separated by normalizing the data with individual coupon stiffness. Damage was measured through an increase in compliance and resulted in a permanent strain after load removel. The current study involves repeated loading. Compliance has been observed to increase with load cycle, while the permanent strain remains small and is neglected.Damage, as a function of load cycle, is incorporated into the non-linear viscoelastic model developed previously for creep/recovery response.Comparisons of the predictive model with experimental data are presented and show good agreement.


American Journal of Physics | 2011

Corked bats, juiced balls, and humidors: The physics of cheating in baseball

Alan M. Nathan; Lloyd V. Smith; Warren L. Faber; Daniel A. Russell

Three questions of relevance to Major League Baseball are investigated from a physics perspective. Can a baseball be hit farther with a corked bat? Is there evidence that the baseball is more lively today than in earlier years? Can storing baseballs in a temperature- or humidity-controlled environment significantly affect home run production? These questions are subjected to a physics analysis, including an experiment and an interpretation of the data. The answers to the three questions are no, no, and yes, respectively.


American Journal of Physics | 2017

Oblique collisions of baseballs and softballs with a bat

Jeffrey R. Kensrud; Alan M. Nathan; Lloyd V. Smith

Experiments are done by colliding a swinging bat with a stationary baseball or softball. Each collision was recorded with high-speed cameras from which the post-impact speed, launch angle, and spin of the ball could be determined. Initial bat speeds were in the range 63–88 mph, producing launch angles in the range 0°–30° and spins in the range 0–3,500 rpm. The results are analyzed in the context of a ball-bat collision model, and the parameters of that model are determined. For both baseballs and softballs, the data are consistent with a mechanism whereby the ball grips the surface of the bat, stretching the ball in the transverse direction and resulting in a spin that was up to 40% greater than would be obtained by rolling contact of rigid bodies. Using a lumped parameter contact model, baseballs are shown to be less compliant tangentially than softballs. Implications of our results for batted balls in game situations are presented.


Journal of Astm International | 2009

Experimental Characterization of Ice Hockey Pucks and Sticks

Rosanna L. Bigford; Lloyd V. Smith

In spite of the broad popularity of ice hockey, little has been done to characterize the performance of pucks or sticks used in play. Data representative of play conditions is particularly lacking. A high speed impact test was developed to measure the puck impact force and coefficient of restitution. Puck brand, temperature, and speed were all shown to have a measurable effect on the relative puck response. The high speed puck test was modified to measure the performance of hockey sticks. The performance of six wood and 11 composite sticks (including different shaft tapers for each group) were compared to evaluate the effect of modern materials on the game. Stick performance was expressed in terms of the maximum puck speed from an idealized slap shot model. In spite of the popularity of the relatively expensive composite sticks, on average the performance of the wood sticks was 10 % higher than the composite sticks. Shaft loading was found to increase the puck speed but did not significantly change the relative performance of the sticks. In contrast to balls in golf and baseball, puck hardness was shown to have a negligible effect on stick performance.

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Derek Nevins

Washington State University

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Jeff Kensrud

Washington State University

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M. Salavatian

Washington State University

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Jeffrey R. Kensrud

Washington State University

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Anita N. Vasavada

Washington State University

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Kasee Hildenbrand

Washington State University

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Brendan Kays

Washington State University

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Scott Burbank

Washington State University

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Warren L. Faber

Washington State University

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Bin Lyu

Washington State University

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