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Joint efficiency is the key to composite structures assembly design, good structures response is dependent upon multi-holes behaviour as subjected to remote loading. Current benchmarking work were following experimental testing series taken from literature on multi-holes problem. Eleven multi-hole configurations were investigated with various pitch and gage distance of staggered holes and non-staggered holes (singlerow holes). Various failure modes were exhibited, most staggered holes demonstrates staggered crack path but non-staggered holes series displayed crack path along net-section plane. Stress distribution were carried out and good agreement were exhibited in experimental observation as reported in the respective literature. Consequently, strength prediction work were carried out under quasi-static loading, most showed discrepancy between 8%-31%, better prediction were exhibited in thicker and non-staggered holes plate combinations.

A study on structures response in multi-holes plates is important to understand the effect of neighbouring hole on stress concentration as subjected to tensile loading prior to bearing failure in multi-bolted joints. Current work implemented experimental framework on staggered and non-staggered multi-holes configurations to include various lay-up types, plate thickness and hole configurations as specified in the testing series. Experimental observations found that all configurations failed in net-section path suggesting that fracture initiates and propagates from the notch tip perpendicular to loading direction in self-similar fashion through the plate thickness. Non-staggered hole configurations demonstrated peak load compared to staggered counterparts due to more congested holes in staggered configurations. Two-dimensional Extended Finite Element Method (XFEM) modelling framework was carried out in all configurations investigated by sufficient meshing refinements, damage stabilization value and boundary conditions. XFEM was extended from classical finite element expression which has enriched function to enable the crack be tracked visually. A physically-based constitutive model from traction-separation relationship was applied and independently measured material properties and in-plane elastic properties were implemented in current work. Strength prediction results showed that good agreement was found in all testing series and showed discrepancies of less than 15%, the best prediction in combination of PX4 lay-ups and staggered multi-holes configurations series.

Single-lap bolted joint is the widely applied technique in joining parts of aerospace and civil engineering structures, due to joint efficiencies where staggered arrangements are commonly adopted. This particular joint type exhibits secondary bending phenomenon due to eccentric loading path. Stress analysis enables the structure engineers to predict the failure path and maximum stress that may lead to catastrophic failures. Stress analysis study were carried out in multi-bolted woven fabric kenaf reinforced polymer (WKRP) joints with variation of lay-up types, hole configurations and plate thicknesses. 3-D FEA modelling implemented here explicitly incorporates out-ofplane deformation to provide better prediction upon crack initiation from maximum stress exhibited along the hole boundary. WKRP plates tested were failed in net-tension where the crack propagated normal to its applied stress. It was found that plate variation (i.e., layup types, hole configurations and plate thicknesses) correspondingly affect tangential stress distributions along its hole boundary. Current 3-D models used modulus properties from independent experimental work which regarded as smeared-out properties through their plate thickness. Staggered configurations demonstrated more evenly stress distribution to their adjacent bolts due to stress resistance diagonally and larger staggered plate width. Slightly contrast in lay-up types where larger tangential stress is exhibited in cross-ply due to more volume fraction of 0° fiber direction. Larger tangential stress in thicker plates associated to effective friction stress transfer to give higher failure load. Effects of secondary bending is more prominent in cross-ply and thinner plates, assumption of smeared-out properties is less good due to plate edge lifting, however, effect of secondary bending phenomenon in multi-bolted is lesser than single-bolted joints.

The use of waste material as a partial replacement has become popular in concrete mixture studies. Many research has utilized waste materials like cement, fine aggregate, coarse aggregate, and reinforcing materials substitute. The current paper focuses on some of the waste elements that are utilized in a concrete mortar (use in roof tile) as a partial replacement for fine aggregates such as rubber ash, sawdust, seashells, crumb rubber, pistachio shells, cinder sand, stone dust, and copper slag. There are many variations of mix proportion and water-cement ratio for every waste material. Compressive strength was compared and found that stone dust and the combination of seashell and coconut fiber shows an incensement when used to replacing fine aggregate. The suitable replacement level for stone dust is 25% and 50%. While the suitable replacement levels for the combination of sea shell and coconut fiber are 20% and 30%. Material from the rubber families such as rubber crumb and rubber ash is only suitable for replacement levels. Rubber families especially rubber crumbs have shown low water absorption value which is good in the production of roofing products. As we know, the roof should have waterproof properties to prevent any leaks from happening when it rains. Most of the waste materials added as fine aggregates in concrete have increased the amount of water absorption and found that sawdust is the most abundant material with a high percentage of water absorption compared to the others. Research on the partial replacement of fine aggregates replaced with waste materials is needed more extensively to provide more confidence about their use in concrete mortars, especially on roof tiles.