Experimental characterization and phenomenological modeling of strainrate-dependent compressive mechanical responses of PVC foams up to 500s-1
Bibliographic record
Abstract
Abstract: Polymeric foams have a ubiquitous presence in modern industrial design due to their unique combination of crucial advantages, including high strength-to-weight ratio, corrosion resistance and significant energy absorbing capacity. Proper understanding and characterization of the dynamic mechanical response of polymeric foams are crucial for safe and optimized engineering design. Therefore, significant research efforts have investigated the rate sensitivity of polymeric foams utilizing various experimental and simulation techniques. The Split Hopkinson Pressure Bar (SHPB) is the most frequently employed apparatus in the dynamic testing of polymeric foams. It is important to note that the SHPBs technique was originally developed for evaluating the mechanical properties of metallic materials with high impedance levels. However, applying this technique for testing soft materials presents a considerable challenge that requires further research and development to overcome. Furthermore, specimens with smaller dimensions (especially when comprised of testing soft materials) are more desirable for SHPB testing. The minimum specimen geometry in accordance with ASTM D1621, the standard test method for compressive properties of rigid cellular plastics, is typically not attainable when utilizing SHPBs. Therefore, in most previous experimental investigations, the specimen geometry requirements by ASTM D1621 were not fulfilled. Technical challenges associated with utilizing SHPBs (and other dynamic testing machines) in testing polymeric foams have resulted in a lack of reliable dynamic material characterization data at strain rates ranging from 50 s-1 to 500 s-1. In this research work, the strain rate sensitivity of PVC foams with nominal densities of 45 kg/m3 and 250 kg/m3 was experimentally investigated utilizing a pneumatic high strain rate testing machine in combination with a novel sacrificial energy absorber. The pneumatic machine was equipped with a bullet, having a mass of 11.5 kg, being massive compared to other pneumatic testing apparatuses considered by other research investigations. Therefore, testing larger foam specimens, enabling conformance to ASTM D1621 requirements at near-constant strain rates, was achieved by employing the described testing machine. The remaining amount of the bullet’s kinetic energy was dissipated by the novel energy absorber to prevent damaging the machine’s structure and the load transducers after foam compaction was achieved. Strain rates up to 500 s-1 were successfully achieved by using this apparatus. A phenomenological model based on the work of Avalle and a modified version of Nagy’s model was proposed to characterize the PVC foams’ rate-sensitive stress/strain response. The model accurately predicted the complete stress/strain response with an average accumulative error of 6.85%.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".