Transient Analysis of EVA Foam Damping and Spatial Optimization of FSR Sensors on Shain Guards

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FORMOSA NEWS - Lampung - Smart Shin Guards: ITERA Scientists Discover Optimal Sensor Placement to Prevent Athlete Injuries. Lower limb injuries in contact sports like football and martial arts pose a significant threat to athletes. High-speed, repeated dynamic impacts often cause microtrauma, soft tissue contusion, and serious tibia stress fractures. To tackle this problem, a research team from the Institut Teknologi Sumatera (ITERA) led by Fahrizal Akbar Herbhakti alongside co-authors Africo Ramadhani, Erny Amalia Lestari, Azry Ayu Nabilah, and Muhamad Ihsan Hufadz conducted a groundbreaking computational study in 2026. They successfully developed an advanced digital framework for Internet of Things (IoT)-enabled smart shin guards. By identifying the precise spatial depth for embedding sensors into protective foam, the ITERA team has effectively bridged the gap between structural durability and signal accuracy, paving the way for next-generation wearable sports safety technology.

The Structural Challenge of Smart Protective Gear
Conventional shin guards made of Ethylene-Vinyl Acetate (EVA) cellular polymer foam are entirely passive. While EVA foam is excellent at dissipating kinetic energy through physical deformation, passive designs cannot provide quantitative data regarding the impact loads athletes receive. This lack of objective data leaves coaches and medical staff in the dark when making critical decisions about player safety, training adjustments, and injury prevention. Transforming these passive guards into active monitoring systems requires embedding a flexible Force Sensitive Resistor (FSR) sensor into the protective EVA foam matrix. When an impact occurs, the mechanical deformation of the foam transfers compressive stress to the FSR sensor, which modulates its electrical resistance to generate tracking data. However, manufacturing these hybrid systems faces a major engineering roadblock: stiffness mismatch. The rigid polyimide substrate of the FSR sensor is thousands of times stiffer than the highly flexible EVA foam surrounding it. If the sensor is planted too close to the surface, extreme shear stress will crack or delaminate the sensor. If it is buried too deeply, the hyperelastic foam absorbs all the kinetic energy, making the data signal too weak to read.

Digital Twin Simulations: Testing Sensor Depths
To eliminate costly and time-consuming trial-and-error manufacturing methods, the ITERA research team designed a precise digital twin model in silico. Using advanced finite element method (FEM) simulations via COMSOL Multiphysics, the scientists coupled solid mechanics and electric currents into a single dynamic computing environment. The computational experiment subjected the digital shin guard model to a peak mechanical impact force of 1,500 Newtons with a contact duration of 20 milliseconds, closely mimicking the real-world kinematics of an intense athletic kick. The team evaluated three distinct sensor embedment depths from the outer surface: 2 mm, 5 mm, and 8 mm.

Key Findings: The 5 Millimeter "Sweet-Spot"
The parametric analysis performed by the ITERA researchers revealed a strict trade-off between signal quality and structural safety across the different depths:

• The 2 mm Depth (Shallow): This configuration yielded a highly sensitive electrical response with an 85% reduction in resistance. However, it caused the interface shear stress to spike to a critical 42.5 MPa, putting the sensor at an immediate risk of mechanical failure and delamination. The resulting signal was also heavily polluted by mechanical noise.
  
• The 8 mm Depth (Deep): This placement provided supreme structural safety, limiting shear stress to just 12.4 MPa. However, the thick layer of EVA foam absorbed too much impact energy, resulting in a weak 25% resistance change that was easily muffled by electronic background noise.
  
• The 5 mm Depth (Optimal): This coordinate emerged as the definitive engineering "sweet-spot". It effectively compressed the interface shear stress to a safe 24.8 MPa well within the durable limits of the polyimide material  while maintaining a robust 62% resistance drop. The resulting signal was clean, linear, and highly reliable.
  

Real-World Impact on Sports Analytics and Medicine
The establishment of the optimal 5 mm depth parameter directly facilitates the integration of smart shin guards into broader cloud-based sports tech networks. In a live deployment, embedded microcontrollers can capture the clean FSR signals, apply the 2.5 ms latency correction, and instantly stream precise impact data to a cloud dashboard via wireless modules. This system offers massive real-world utility for the sports industry. Athletic coaches receive real-time telemetry on smartwatches or tablets, allowing them to modify training intensities or substitute fatigued players before an injury occurs. Medical teams gain access to an intelligent Decision Support System (DSS) that calculates cumulative mechanical doses, tracks long-term electronic health histories, and offers quantitative data for evidence-based diagnosis and rehabilitation. According to the research team at the Institut Teknologi Sumatera (ITERA), utilizing integrated multiphysics modeling to pinpoint these parameters ensures long-term wearable durability while serving as an essential foundation for modern, predictive sports safety ecosystems.

Author Profile
Fahrizal Akbar Herbhakti, S.T., M.T. is a lead researcher and lecturer in the Sports Engineering Study Program at the Institut Teknologi Sumatera (ITERA). His field of expertise focuses on multiphysics computational modeling, smart materials, and the development of intelligent sports instrumentation.
Africo Ramadhani, Erny Amalia Lestari, Azry Ayu Nabilah, and Muhamad Ihsan Hufadz are computational and systems engineering researchers at the Institut Teknologi Sumatera (ITERA), specializing in embedded sensor networks and protective polymer mechanics.

Source:
Herbhakti, F. A., Ramadhani, A., Lestari, E. A., Nabilah, A. A., & Hufadz, M. I. (2026). Transient Analysis of EVA Foam Damping and Spatial Optimization of FSR Sensors on Shin Guards. Formosa Journal of Computer and Information Science (FJCIS), 5(1), 187-200.
DOI: https://doi.org/10.55927/fjcis.v5i1.16645
URL: https://journal.formosapublisher.org/index.php/fjcis