Q2. What is the corresponding shear fracture toughness?
The corresponding shear fracture toughness is mainly attributed to the complex failure modes involving fibre tensile failure, fibre pull-out, fibre/matrix interface debonding, delamination and following fibre bending fracture.
Q3. What is the effect of the shear deformation on the fibres?
As the shear deformation increases, the voids and fibres rotate towards the direction of crosshead movement, while the fibres pick up loading under tension.
Q4. What is the overall material behaviour under in-plane shear loading?
The overall material behaviour under in-plane shear loading consists of matrix yielding, matrix cracking, fibre rotation, fibre breakage, and delamination.
Q5. What are the disadvantages of the laminate-scale model?
models developed at laminate-scale level have three main disadvantages: loss of accuracy, loss of generality, and increased number of material properties, i.e. parameters need to be remeasured for different layups and geometries.
Q6. What is the expected damage of a continuous fibre composite?
The anticipated damage will occur in the form of net fibre pull-out and breakage in tension and predominantly fibre kink band formation when loaded in compression.
Q7. How was the critical specific work of fracture determined?
The critical specific work of fracture under shear loading was determined by linear regression of 𝑤𝑓 values to zero ligament thickness.
Q8. What was the failure of the V-90 specimens?
The V-90˚ specimens failed at very low strain with a crack propagating through the matrix in the central notch area with little plastic deformation.
Q9. What is the main reason why the matrix can experience large plastic deformation without cracking?
It is noted that the matrix can experience large plastic deformation without cracking, while the fibre can carry load and maintain overall integrity until the failure strain is reached.
Q10. How was the energy dissipated by delamination determined?
The energy dissipated by delamination was determined by multiplying the mode II interlaminar fracture toughness 𝐺𝐼𝐼𝑐 by the delaminated area, 𝑊𝑑𝑒𝑙 = 4𝐺𝐼𝐼𝑐𝐴3.
Q11. What was the important factor in the determination of the fracture toughness?
The measured fracture toughness was also validated in terms of dissipated fracture energy using the area method with a cohesive fracture surface.
Q12. What was the effect of the loading-unloading cycle on the plastic fibres?
Several consecutive loading-unloading cycles were applied to specimens, and considerable permanentshear plastic strain was observed.
Q13. What is the main mechanism raising the toughness of fibre composites?
The main energy-dissipating mechanism raising the toughness of fibre composites could be the extensive fibre breakage, interfacial debonding and fibre pull-out events evident in Fig. 11 and Fig. 12.
Q14. What is the initiation of cracking in unidirectional laminate specimens?
The initiation of cracking in unidirectional laminate specimens, at relatively low loading, suggests that these specimens are not appropriate for the fullcharacterisation of the non-linear behaviour of the composite laminate.
Q15. What was the dominant failure mode of the matrix?
Details of the failure process can be seen in Fig. 5, where matrix cracking was the dominant failure mode, accompanied by fibre rotation, fibre pullout and fibre breakage in the final stages.
Q16. What is the relationship between shear modulus and the elastic properties of the fibres?
This also confirms that the shear modulus is controlled by matrix deformation and fairly independent of fibre properties, while the linear hardening region relies on the elastic properties of the fibres.