## 1 The Evolution of Sports: A Synergy of Historical Development and Technological Innovation
Their outstanding strength-to-weight ratio and fatigue resistance make them key materials in advanced manufacturing fields. However, minor differences in manufacturing processes can significantly affect the final \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sports Equipment** & **Primary Materials** & **Material Category** & **Key Applications** \\ \hline \multirow{2}{*}{Basketball/Soccer/Volleyball} & \multirow{2}{*}{Rubber, PU/PVC Leather} & \multirow{2}{*}{Polymer Materials} & Outer layer: PU synthetic \\  & & & leather; Inner bladder: butyl \\  & & & rubber \\ \hline \multirow{2}{*}{Badminton Racket} & \multirow{2}{*}{Carbon Fiber, Titanium Alloy} & \multirow{2}{*}{Composite + Metallic} & Frame: carbon fiber \\  & & & composite; Shaft: titanium \\  & & & alloy or carbon fiber \\ \hline \multirow{2}{*}{Tennis Racket} & \multirow{2}{*}{Carbon Fiber, Kevlar} & \multirow{2}{*}{Composite Materials} & Main body: carbon \\  & & & fiber-reinforced epoxy resin; \\  & & & Some include Kevlar for \\  & & & toughness \\ \hline \multirow{2}{*}{Golf Club} & \multirow{2}{*}{Titanium Alloy, Carbon Fiber} & \multirow{2}{*}{Metallic + Composite} & Clubhead: titanium alloy; \\  & & & Shaft: carbon fiber composite \\ \hline \multirow{2}{*}{Bicycle Frame} & \multirow{2}{*}{Aluminum/Carbon Fiber/Titanium} & \multirow{2}{*}{Metallic + Composite} & Entry-level: aluminum alloy; \\  & & & Racing: carbon fiber; \\  & & & High-end: titanium alloy \\ \hline \multirow{2}{*}{Treadmill Belt} & \multirow{2}{*}{Rubber + Nylon Fiber} & \multirow{2}{*}{Polymer + Composite} & Surface: anti-slip rubber; Base \\  & & & layer: nylon fiber \\  & & & reinforcement \\ \hline Swimmingoggles & Polycarbonate (PC), Silicone & Polymer Materials & Lens: PC; Seal: silicone \\ \hline \multirow{2}{*}{Skis} & \multirow{2}{*}{Wood + Fiberglass + Polyethylene} & \multirow{2}{*}{Composite Materials} & Core: wood; Reinforcement: \\  & & & fiberglass; Base: \\  & & Polyethylene & ultra-high-molecular-weight \\  & & & polyethylene \\ \hline \multirow{2}{*}{Dumbbells/Barbells} & \multirow{2}{*}{Cast Iron, Steel} & \multirow{2}{*}{Metallic Materials} & Main body: cast iron \\  & & & (chrome-plated); Bar: \\  & & & chromium-molybdenum steel \\ \hline \multirow{2}{*}{Climbing Rope} & \multirow{2}{*}{Nylon, Polyester} & \multirow{2}{*}{Polymer Materials} & Core: braided nylon fibers; \\  & & & Outer sheath: polyester \\ \hline \multirow{2}{*}{Table Tennis Ball} & \multirow{2}{*}{Celluloid/ABS Plastic} & \multirow{2}{*}{Polymer Materials} & Professional: celluloid; \\  & & & Training: ABS plastic \\ \hline \multirow{2}{*}{Ice Skates} & \multirow{2}{*}{Stainless Steel + Carbon Steel} & \multirow{2}{*}{Metallic Materials} & Blade: high-carbon stainless \\  & & & steel; Holder: alloy steel \\ \hline \multirow{2}{*}{Sports Protective Gear (Knee  Pads, etc.)} & \multirow{2}{*}{EVA Foam + Nylon Fabric} & \multirow{2}{*}{Polymer + Composite} & Cushioning: EVA foam; Outer \\  & & & layer: nylon/PU-coated fabric \\ \hline \multirow{2}{*}{Baseball Bat} & \multirow{2}{*}{Aluminum Alloy/Maple Wood/Composite} & \multirow{2}{*}{Metallic + Natural + Composite} & Professional: aluminum alloy; \\  & & & Traditional: maple wood; \\  & & & Advanced: carbon fiber + \\ \hline \multirow{2}{*}{Climbing Carabiners} & \multirow{2}{*}{Aluminum Alloy} & \multirow{2}{*}{Metallic Materials} & Aerospace-grade aluminum \\  & & & alloy \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Sports equipment and their material classifications. performance: Unidirectional braided (UD) maximizes axial stiffness through the parallel arrangement of fibers and is widely used in linear load-bearing components such as bicycle frames, but its obvious anisotropy is prone to delamination failure; bidirectional braided (BD) adopts an orthogonal fiber network design to achieve a balance of mechanical properties in the X/Y axis direction.