Experimental Investigation of Thermal Properties of Coir-Based Epoxy Composites

Abstract

Natural-fibre-reinforced polymer composites are being investigated for applications that require a balance of thermal response, manufacturability and material-resource efficiency. This study organizes and critically evaluates the thermal-property results reported for epoxy-based composites associated with coconut coir and glass fibre. The source apparatus comprises an aluminium–composite–plywood layered assembly, a nominal heater input of 30 W and nine temperature-measurement locations. Using the calculations recorded in the thesis, the reported thermal-conductivity estimates are 1.12, 0.91 and 0.89 W m?¹ K?¹ for specimens labelled as containing 4, 20 and 8 g of coir, respectively. A separate six-entry summary table reports conductivity decreasing from 0.90 to 0.68 W m?¹ K?¹ across nominal reinforcement levels 0–100, equivalent to a 24.4% endpoint decrease within that table. These two result groups are not directly comparable because the reinforcement basis and specimen mapping are not documented consistently. The specific-heat values also require recalculation because the source uses a power value without specifying heating duration or absorbed energy. The study therefore presents a transparent preliminary analysis, derives the relevant series thermal-resistance formulation and identifies the measurement records required for validation. The current evidence indicates variation among reported values but does not establish a statistically supported composition–conductivity relationship or confirm suitability for a specific insulation application.

Introduction

This study examines the thermal properties of epoxy composites reinforced with coconut coir and glass fibre, focusing on thermal conductivity and the reliability of the numerical results reported in the supplied thesis. Natural fibres such as coconut coir are attractive because of their availability and resource-efficiency benefits. However, their performance depends on fibre treatment, composition, fibre–matrix bonding and manufacturing conditions.

The study documents a layered experimental arrangement consisting of a 4 mm aluminium plate, a 6 mm composite specimen and a 4 mm plywood layer. A nominal 30 W heater and nine temperature measurement locations (T1–T9) were described. Fourier’s law and a series thermal-resistance model were used to estimate conductivity.

Key Results

Two separate sets of conductivity results were reported:

1. Worked-example calculations: Conductivity values were 1.12 W/m·K for the specimen labelled 4 g coir, 0.91 W/m·K for 20 g coir and 0.89 W/m·K for 8 g coir. The 4 g specimen showed the highest reported value.

2. Separate summary table: Conductivity decreased from 0.90 to 0.68 W/m·K across nominal reinforcement levels of 0 to 100, representing a reported reduction of approximately 24.4%. Thermal diffusivity increased from 4.12 to 12.40 × 10?? m²/s over the same series.

These two datasets were kept separate because their specimen labels, trends and numerical values could not be reconciled using the available information.

Reliability and Limitations

The reported thermal properties cannot yet be considered fully validated because important experimental details are missing. These include the exact composite composition, fibre treatment, sensor positions, temperature units, actual heat-transfer rate, calibration details and measurement uncertainty. The nominal 30 W electrical heater input was used in calculations without establishing how much heat actually passed through the composite.

Additionally, specific heat calculations lack clearly documented units and heating duration. Thermal diffusivity and resistance values also require further verification. No statistical analysis was performed because independent specimen replicates were not clearly identified.

Required Improvements

• Document the exact quantities of coir, glass fibre, epoxy resin and hardener.

• Provide a dimensioned sensor arrangement and calibrated temperature measurements.

• Measure the actual heat flow and account for environmental heat losses.

• Reconcile all graphs and tables using the original experimental dataset.

• Measure density and specific heat using appropriate methods.

• Conduct repeat experiments and report measurement uncertainty.

Conclusion

This manuscript has organized the available experimental record for epoxy-based composites associated with coconut coir and glass fibre and evaluated the reported thermal-property calculations. The source’s worked examples give conductivity estimates of 1.12, 0.91 and 0.89 W m?¹ K?¹ for specimens labelled as containing 4, 20 and 8 g of coir. A separate summary table reports conductivity decreasing from 0.90 to 0.68 W m?¹ K?¹ across six nominal levels, a 24.4% endpoint decrease within that table. These datasets have been retained separately because the specimen mapping and reinforcement basis are not documented consistently. A layered thermal-resistance model was stated to show how composite conductivity may be calculated from geometry, boundary temperatures and heat rate. Its application remains conditional on steady one-dimensional conduction, verified layer dimensions, known reference properties, a mapped sensor arrangement and correction for contact resistance and heat loss. The specific-heat calculation is dimensionally incomplete because the source uses a power value without a documented time interval, and the diffusivity and resistance values therefore require verification. Accordingly, the available evidence supports only a preliminary assessment that the reported formulations exhibit different thermal responses. It does not establish a validated optimum composition, statistical significance, or suitability for a particular insulation application. The immediate next steps are to reconcile the raw data, document every formulation, measure actual electrical input and heating duration, calibrate the temperature sensors, repeat tests on independent specimens and report uncertainty. Only after these steps should the final conductivity, specific heat and diffusivity values be used for material selection.

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Copyright

Copyright © 2026 Seeta Rama Swamy, Lakshmi Tulasi Chavali, Ravi Kumar Boddu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.