This study presents a systematic evaluation of the dimensional accuracy and process capability of fused deposition modeling (FDM) additive manufacturing, with emphasis on the influence of process‐induced thermal and kinematic effects on dimensional performance. Two geometries made of polylactic acid (PLA) were considered: a staircase specimen to assess process capability and directional effects, and a geometric benchmark test artifact (GBTA) to evaluate dimensional reliability across representative features. Measurements were performed using a digital caliper for the staircase model and a coordinate measuring machine (CMM) for the GBTA. Under manufacturer‐recommended, unoptimized printing conditions, staircase analysis showed that the investigated FDM system achieved process performance indices ( P m and P m k ) ≥ 1.33 at a 95% confidence level. Dimensional stability varied across the build chamber due to spatially nonuniform cooling conditions, with statistically significant position‐dependent deviations observed particularly along the build direction. Larger features exhibited higher relative precision. Achievable ISO 286‐1 International Tolerance grades ranged from IT9 to IT14. GBTA results confirmed systematic undersizing of cylindrical and curved features. Absolute dimensional deviations remained approximately constant across nominal sizes, whereas percentage errors increased for smaller features due to scale effects. Despite these variations, the geometric form was preserved, demonstrating high repeatability. The proposed capability‐based evaluation framework provides a structured approach to quantifying dimensional reliability in polymer‐based material extrusion processes for functional components.
Three‐dimensional (3D) printing has transformed medical engineering by enabling customized bone prostheses. This study designs and evaluates a 3D‐printed femur segment with manually crafted porosity mimicking natural bone tissue. Mechanical performance is assessed through compression testing, dynamic simulation, fatigue analysis, and crack propagation. Compression tests yielded average fracture force of 9.456 kN, stress of 11.76 MPa, strain of 8.68 mm, and energy of 42.6 kJ. The biomimetic porosity showed superior resistance compared to alternatives. Fatigue simulations indicated infinite life under in vivo loads. Crack simulations at failure sites showed stresses of 12.82 and 11.89 MPa. Findings highlight biomimetic designs′ potential in bone tissue engineering.
The recent trends have seen natural fiber–reinforced composites (NFRCs) garnering a large following due to their low density, commercial viability, low health risk, high tensile strength and modulus, and renewability. This paper discusses the thermal properties such as the thermal conductivity, heat deflection temperature, thermal stability, and dielectric strength of kenaf‐reinforced bulk molding compound (BMC). The Lewis–Nielsen method was used to calculate theoretical values and compare with the experimental values. It has been found that the average thermal conductivity decreases as the fiber loading increases for all fiber lengths. The highest was observed in the BMC reinforced with 9‐mm kenaf short fiber, with a value of 0.42. It has also been found that the heat deflection temperature decreases proportionally to the loading of the fiber due to varied fiber stress loading in the material. It was also found that fiber length did not play a significant part in the heat deflection temperature. From the DSC and TGA results, it can be said that thermal stability is preserved for all materials and peaks at 12 mm 20%. However, dielectric strength was found to be directly proportional to fiber loading as well as fiber length. The highest was at 15 mm 30% loading. It can be concluded that both fiber loading and fiber length play a significant part in the thermal and electrical properties of the composites.
Carbon fiber–reinforced polymers (CFRPs) have gained widespread use across the aerospace, automotive, and energy sectors due to their high strength‐to‐weight ratio. Many structural applications require joining CFRPs to aluminium alloys, with adhesive bonding offering several advantages over mechanical joining methods, including uniform stress distribution and compatibility with CFRPs. Among various strategies to improve bond strength, surface preparation plays a critical role. This study investigates the effect of chemical etching on CFRP using sulfuric acid solution to enhance bond strength in single‐lap joints with aluminium alloys when tested in lap shear test. Experimental results show that optimised chemical etching can triple the lap shear strength compared with untreated samples. Acid concentration significantly influences joint performance; furthermore, the soaking method of etching can yield stronger bonds than the pipette method. Additionally, chemically etched CFRP–Al joints can outperform those treated with conventional sandpaper abrasion. These findings demonstrate the effectiveness of controlled chemical etching in improving the structural integrity of CFRP–metal adhesive joints and provide insights for designing more robust hybrid structures for lightweight applications.
The increasing incorporation of biodegradable plastics into conventional recycling streams has raised concerns regarding their influence on the performance of recycled polymers. In particular, the presence of polylactic acid (PLA) in recycled high‐density polyethylene (rHDPE) may significantly affect mechanical stability during reprocessing and environmental exposure. This study systematically evaluates the combined effects of PLA content (0–50 wt%), recycling cycles, exposure time, and aging conditions (natural and accelerated) on the mechanical performance of rHDPE/PLA blends using a multilevel full factorial experimental design comprising 96 experimental runs. Tensile stress, elongation at break, and impact resistance were measured according to ASTM standards. Statistical analyses including ANOVA, regression modeling, and interaction analysis were applied to identify significant factors and combined effects, followed by multiresponse optimization using a desirability‐function approach. PLA incorporation produced a drastic reduction in ductility and toughness, with elongation at break decreasing by more than 95% and impact resistance by approximately 80%–85% as PLA content increased from 0 to 50 wt%. Accelerated aging generated the most pronounced reduction in tensile strength, with decreases on the order of 20%–30% compared with natural aging conditions. Recycling cycles further contributed to mechanical degradation, although to a lesser extent. Significant interaction effects among composition, recycling cycle, and aging environment demonstrated that mechanical degradation results from synergistic thermo‐oxidative, processing‐induced, and interfacial incompatibility mechanisms. The results provide a comprehensive statistical framework for understanding the degradation behavior of rHDPE systems contaminated with biodegradable polymers and support the identification of optimal operating conditions for maximizing the mechanical performance of recycled polymer blends.
